Search

The cognitive process of innovation in animals produces new or modified behaviours in response to new challenges. Common raccoons rely on their problem-solving ability to exploit anthropogenic resources that are not freely available. As a result, they are often involved in human–wildlife conflict. We used two food extraction tasks of varying difficulty levels to measure problem-solving ability in wild raccoons living in three Canadian protected areas. We conducted experiments in two distinct locations within each park based on human footprint: recreation and preservation zones. We also looked at the effect of the presence of conspecifics and of two behavioural traits (exploratory diversity and persistence) on performance. Performance differed between the puzzles, with one of them being easier to solve based on success rate and time to success. The zone (presence of humans) did not affect problem-solving performance, while there was a tendency for solving time to increase with the presence of conspecifics. Exploratory diversity was positively related to success rate and time taken to solve. Contrary to predictions, persistence did not improve performance. There were also individual differences in performance in term of success rate and time to completion. We encourage using multiple concurrent tests to evaluate problem solving with wild individuals. Overall, we provide additional evidence that raccoons are apt problem-solvers, with the potential to adapt to new foraging opportunities, and a relevant species to study innovation in mammals. • We measured problem-solving ability in wild raccoons using food-extraction tasks. • Performance greatly differed between tasks, but exposure to humans had no effect. • Solving time increased with the presence of conspecifics. • Increase in exploratory diversity improved success rate and reduced solving time. [ABSTRACT FROM AUTHOR]

Behavioural lateralization is widespread across animal taxa. Consistent with the idea that lateralization indicates advantageous specialization of the brain hemispheres, individuals with more lateralized behaviour are often found to have better cognition. Among-individual differences in behavioural lateralization nevertheless exist, sometimes associated with differences in other phenotypic traits. Knowing which phenotypes are associated with behavioural lateralization gives cues as to why differences in lateralization exist within populations, but past research has often focused on one or a few phenotypes, and found different, sometimes opposed, correlations with lateralization. Here, we assayed behavioural lateralization of common waxbills, Estrilda astrild , in a feeding task, to test for associations with phenotypic differences, using a broad set of traits that might influence or be influenced by lateralization: a cognitive trait (inhibitory control), size, personality, social dominance, cues of stress and sex. Most individuals consistently fed with the right side towards the food, resulting in a population level right-side lateralization. However, evaluating photographs from waxbills feeding in the wild worldwide, we found no evidence of a preferred feeding side, contrasting with results in our population. There were also differences between individuals in our population in the direction and strength of lateralization. Females were, on average, more right-side lateralized than males, and there were larger among-individual differences in lateralization among males. None of the phenotypes studied predicted differences in the strength of lateralization. However, individual differences in the direction of lateralization were related to inhibitory control, an aspect of cognition, more strongly so in males than in females. These are among the few results indicating that the direction of behavioural lateralization, rather than its strength, is associated with cognitive differences among individuals. It is also the first time that a sex-dependent association between behavioural lateralization and cognitive performance has been found, suggesting that sex-specific functions are implicated in maintaining differences in behavioural lateralization. • It is still not clear why individuals differ in behavioural lateralization. • We studied the direction and strength of common waxbill behavioural lateralization. • Most individuals fed preferentially with their right side from a feeder. • We found sex differences in lateralization and, in males, associations with cognition. • Sex-specific functions may thus help maintain differences in lateralization. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) offer invaluable contributions to wildlife observation, reducing costs and human risk while minimizing disturbance to animals during aerial surveys. However, within a population, individual animals can exhibit different responses to UAVs. This indicates that the level of UAV disturbance might differ between individuals even when the disturbance is mild at the population level. However, few studies have investigated UAV disturbance at the individual level. In this study, we explored the variation in response to UAVs among individual Weddell seals along the Terra Nova Bay coastline in Antarctica. We also examined how internal factors such as age, group composition and whether their eyes were open, as well as external factors such as UAV flight schemes, influenced responses. Our findings showed substantial variation among individual seals in both their overall response and changes in response to descending UAVs. Notably, seals were more sensitive to UAVs with vertical flight schemes than to those with horizontal flight schemes. When seals were in groups or had their eyes closed, their vigilance responses to UAVs decreased. Therefore, our findings highlight the importance of not only considering individual factors but also avoiding vertical flight patterns during UAV-based aerial surveys of Weddell seals, thus minimising disturbance. Additionally, we recommend developing more effective approaches for wildlife research that utilize UAVs by incorporating the consideration of individual differences in responses to UAVs. • UAV effects on wildlife rarely focus on individual impacts. • Individual Weddell seals' responses to UAVs varied. • UAV vertical flights made seals more vigilant than horizontal flights. • Seals in groups or with closed eyes showed less UAV vigilance. • Consider both individual states and UAV flight patterns to reduce disturbance. [ABSTRACT FROM AUTHOR]

Dispersal is critical to population persistence, colonization and connectivity which are all critical components of invasive success. While individual propensity to disperse varies within populations, the underlying mechanisms promoting individual dispersal remain unclear. Collectively, dispersal is influenced by the environment and individual phenotype. Here we investigated individual dispersal propensity in the Trinidadian guppy, Poecilia reticulata , and related individual variation in dispersal behaviour to phenotype and social/environmental conditions. Namely, we addressed the effect of sex ratio (social/environmental factor) on the tendency for individuals to disperse across physical barriers via jumping behaviour. Jumping is vital for the dispersal of many aquatic species and has been anecdotally linked to the guppy's global invasive success. We found similar jumping behaviour for males and females, with population sex ratio not influencing the magnitude of male or female dispersal. Further, we found consistent among-individual variation in jumping probability; individual differences explained 17.46% and 7.92% of total variation in jumping probability for males and females, respectively. These results strongly indicate that sex ratio does not influence jumping behaviour, suggesting that species invasions are mediated by a nonrandom subset of individuals with greater dispersal tendencies. Overall, this study stresses the need to move the focus of invasion biology from the species level to incorporate information on individual variation in behaviour. • Guppies differ in individual propensity to disperse over physical barriers. • Sex ratio does not influence jumping behaviour. • Species invasions are mediated by individuals with greater dispersal tendencies. [ABSTRACT FROM AUTHOR]

An individual's future behaviour and fitness are strongly influenced by early life experience. Within the suite of factors that underpin juvenile development, sleep plays a particularly important role, fulfilling vital physiological and cognitive functions. Sleep ontogeny is the process by which sleep time becomes shorter and more consolidated into fewer bouts from in utero development to adulthood; however, how sleep quantity, fragmentation and quality develop in neonates in the wild is unknown. We investigated this question in 19 free-ranging fallow deer fawns, Dama dama , during the first 5 weeks of life. Specifically, we examined how sleep developed, how it differed between and within individuals, and how it was affected by environmental conditions, using accelerometer-derived estimates of sleep and a Bayesian hierarchical modelling approach. We showed that sleep duration rapidly decreased and became more consolidated, quickly approaching an adult-like condition. Moreover, fawns exhibited consistent individual differences in sleep quantity, fragmentation and quality, as well as in the rate at which sleep developed. Finally, environmental conditions affecting thermoregulation mediated sleep behaviour; sleep time was reduced and was of lower quality on warmer days, and sleep quality was further compromised in more humid conditions but was higher with greater rainfall. While sleep ontogeny in free-ranging fawns is partially shaped by the environment, our study reveals previously unknown individual differences in sleep behaviour present from birth, and in the rate of sleep development. We suggest that such individual differences may represent pace-of-life syndromes and may have important consequences for individual fitness later in life. • Fallow deer fawns' sleep rapidly decreases and consolidates in their first 5 weeks. • Fawns differ in sleep patterns and the rate of development from birth. • High temperature and humidity impair fawns' sleep. • Individual differences in sleep ontogeny may be related to pace-of-life syndromes. • Minimally invasive biologging is a viable approach to studying sleep in the wild. [ABSTRACT FROM AUTHOR]

Caching food for later retrieval is vital for many animals' survival, but little is known about how this behaviour varies among individuals in the wild. If individuals consistently differ in where, when and how they store food, it could indicate that caching is subject to selection. In this study, we experimentally quantified the repeatability and relationship between different aspects of caching behaviour over two winter seasons in a wild population of toutouwai, Petroica longipes. Individuals were repeatable both within and between years in the number of cache sites they created, the distance they travelled to cache and food item handling time prior to caching. All three of these caching behavioural measures were positively correlated with one another, suggesting that toutouwai exhibit a caching syndrome analogous to a behavioural syndrome, with individuals ranging between 'clump caching' and 'scatter caching'. The number of food items that birds ate prior to caching and latency to begin cache retrieval were also consistently correlated, indicating a second 'fast - slow' syndrome linking cache retrieval to satiation level. In both syndromes most individuals were normally distributed between the behavioural extremes, indicating that birds tended to partake in intermediate caching rather than clustering at either end of the continuum. We posit that this distribution may be the result of stabilizing selection that balances the costs and benefits of each extreme. • Toutouwai are repeatable in numerous aspects of food-storing behaviour. • Different measures of caching behaviour consistently correlate with one another. • Individuals fall along an axis between 'scattering' and 'clumping' caching types. • An intermediate caching type may be maintained by stabilizing selection. [ABSTRACT FROM AUTHOR]

In cannibalistic species, conspecifics can be both predators and prey. As a result, conspecifics present a unique conflict at the intersection of predation, competition and nutritional resources in these species. To better understand how individuals respond to the complex information of conspecific chemical cues, we studied aggressive and cannibalistic tadpoles of the dyeing poison frog, Dendrobates tinctorius. We used a standardized open field test to compare behavioural responses to a positive cue (food), a negative cue (predator) and two conflicting cues (conspecific density and injured conspecifics). We specifically used chemical cues to understand how individuals respond in the absence of additional information that would disambiguate their status as conspecific predator versus prey. We found that the injured conspecific cue elicited a response distinct from either the food cue or the predator cue: tadpoles explored more relative to baseline and predator cues but spent less time moving compared to the food cue. We suggest that these patterns reflect cue-dependent behavioural strategies that maximize exploration while minimizing detection in the presence of conspecific cannibals. In addition to cue-specific changes in behaviour, we observed consistent differences in individuals' behaviour across environments and found that activity and exploratory behaviour were positively correlated across environments. Taken together, our results demonstrate that conspecific cues are interpreted as distinct from either food cues or predator cues in a cannibalistic species where they can represent both. • In cannibalistic species, conspecifics can be both predators and prey. • Therefore, chemical cues of conspecifics provide conflicting information. • Cannibalistic tadpoles exhibited distinct behavioural responses to conspecific cues. • Tadpoles also showed consistent individual differences across contexts. [ABSTRACT FROM AUTHOR]

Identity cues in animal calls are essential for conspecific vocal individual recognition. Some acoustically active species mainly show reliable identity cues in their vocalizations because of variation in anatomy and life history. Long and strenuous-to-produce vocalizations may be particularly effective for showing identity cues because sustaining such calls may reveal individual anatomical differences in sound production. It is largely unknown whether reptiles possess acoustic individuality despite some groups being vocal. We analysed 814 bellows from 47 American alligators, Alligator mississippiensis , extracting spectral characteristics and manually corrected contours of the fundamental frequency. Recognition was up to 66% correct with a supervised classifier (random forest) and 61% with unsupervised clustering (chance = 2.1%), indicating that individual alligators have highly distinct bellows. Alligators were distinguished primarily based on the call spectrum, fundamental frequency contour and amplitude modulation, which also provided information about the animal's size. Neither manual supervision of acoustic analyses nor supervised training on labelled data was necessary to achieve reasonable accuracy, which has promising potential for identification of individuals via passive acoustic monitoring for research and conservation purposes. Additionally, our results highlight the importance of studying the utilization of acoustic individuality in the social lives of crocodylians. • The bellows of American alligators are highly individually distinct. • Classification algorithms can identify American alligators based on their bellows. • Acoustic individuality likely comes from anatomical differences between individuals. • This analytical method has potential for passive acoustic monitoring of Crocodylians. • Crocodylians may utilize such acoustic individuality in their social lives. [ABSTRACT FROM AUTHOR]

• We identified the linear association of co-expressed, immune-related genes to the strength of depression-like immobility behaviors of individual animals by an in-depth transcriptomic study of the mouse PFC. • The involvement of epigenetic changes in similar genes in patients with MDD was identified, which showed correlations to the thinning of cortical regions. • Our results highlighted the possible involvement of the interferon pathway, especially USP18, in the neuroinflammation-related pathophysiology of depression. A growing body of evidence suggests that immune-related genes play pivotal roles in the pathophysiology of depression. In the present study, we investigated a plausible connection between gene expression, DNA methylation, and brain structural changes in the pathophysiology of depression using a combined approach of murine and human studies. We ranked the immobility behaviors of 30 outbred Crl:CD1 (ICR) mice in the forced swim test (FST) and harvested their prefrontal cortices for RNA sequencing. Of the 24,532 analyzed genes, 141 showed significant correlations with FST immobility time, as determined through linear regression analysis with p ≤ 0.01. The identified genes were mostly involved in immune responses, especially interferon signaling pathways. Moreover, induction of virus-like neuroinflammation in the brains of two separate mouse cohorts (n = 30 each) using intracerebroventricular polyinosinic:polycytidylic acid injection resulted in increased immobility during FST and similar expression of top immobility-correlated genes. In human blood samples, candidate gene (top 5%) expression profiling using DNA methylation analysis found the interferon-related USP18 (cg25484698, p = 7.04 × 10−11, Δβ = 1.57 × 10–2; cg02518889, p = 2.92 × 10−3, Δβ = − 8.20 × 10–3) and IFI44 (cg07107453, p = 3.76 × 10–3, Δβ = − 4.94 × 10–3) genes to be differentially methylated between patients with major depressive disorder (n = 350) and healthy controls (n = 161). Furthermore, cortical thickness analyses using T1-weighted images revealed that the DNA methylation scores for USP18 were negatively correlated with the thicknesses of several cortical regions, including the prefrontal cortex. Our results reveal the important role of the interferon pathway in depression and suggest USP18 as a potential candidate target. The results of the correlation analysis between transcriptomic data and animal behavior carried out in this study provide insights that could enhance our understanding of depression in humans. [ABSTRACT FROM AUTHOR]

In a variant of Hylland and Zeckhauser (1979) 's model that allows agents to start out with different endowments, we develop a pseudo-market procedure that allows the policymaker to decide to what extent individual endowment differences shall be balanced by the average endowment. Our procedure sidesteps the known non-existence problem of Walrasian equilibria, and finds an efficient and balanced individually-rational allocation. Envy in our procedure is justified in a utilitarian sense: an envying agent's endowment must make a lower contribution to standard weighted utilitarian welfare than that of the envied agent. [ABSTRACT FROM AUTHOR]

Individuals of the same species often show consistent differences in behaviour, categorized as personalities. For an animal with parental care, reproductive success may be affected by the behaviour of the parent. When reanalysing a previously published field study, I found that nest-guarding male common gobies, Pomatoschistus microps , showed individual differences in behavioural response to disturbance during simulated predation risk. There was also a difference in nesting success with some nests being abandoned prematurely. The males were tested over a nesting cycle with respect to individual behaviour patterns. Two behaviours were quantified, in the presence of a live eelpout, Zoarces viviparus , behind glass: (1) time away from nest after being evicted by the approach of a finger, and (2) the distance between the finger and the nest when the male escaped from the nest. Of 24 males studied, only half remained in their nest for the whole nesting cycle, while the other nests were abandoned earlier, failing in the current reproductive event. No direct effects of behaviour were found in males that abandoned early or remained at the nest for the full nesting cycle. However, larger males stayed away from the nest for longer and more often abandoned their nests prematurely than smaller males. This may be explained by a better competitive ability to renest for a larger male. Behaviour, but not nesting success, was also connected with brood size. Males with smaller broods stayed away from the nest for longer. Nesting success thus seemed to result from a combination of size and male personality. • Nesting male common gobies showed consistent individual differences in behaviour. • Larger males abandoned the nest prematurely more often than smaller ones. • Larger males stayed away from the nest for longer than smaller males. • Behaviour pattern and size seem to affect reproductive success. [ABSTRACT FROM AUTHOR]

The distance at which animals move away from threats, flight initiation distance (FID), is often used to study antipredator behaviour and risk assessment. Variation in FID is explained by a variety of internal and external biotic and physical factors, including anthropogenic activities. Most prior studies focused on unidentified individuals, so our understanding of the fitness consequences of FID is relatively limited. We asked whether consistent individual differences in variation in flight initiation distance is associated with variation in summer survival and/or winter survival in an individually marked population of yellow-bellied marmots. We found no clear association between flight initiation distance and summer survival or winter survival. This suggests that FID decisions, while demonstrably optimizing current survival, may not have longer-term fitness consequences. Our results may be explained by the relatively modest repeatability of FID or it may have emerged from our attempt to explain longer-term measures of fitness. Future studies of the fitness consequences of personality traits should pay particular attention to the time interval between measuring the individuality of a trait and examining its fitness consequences. • We examined fitness consequences of flight initiation distance (FID) in marmots. • FID was modestly repeatable in individually marked yellow-bellied marmots. • However, we found no association between FID and summer or winter survival. • For marmots, fleeing had immediate but not longer-term survival benefits. • Future studies should focus on the timing of measures of repeatability and fitness. [ABSTRACT FROM AUTHOR]

Ideal free distribution theory attempts to predict the distribution of well-informed ('ideal') and unconstrained ('free') foragers in space based on adaptive individual decisions. When individuals differ in competitive ability, a whole array of equilibrium distributions is possible, and it is unclear which of these distributions are most likely. In the first part of our study, we show that strong competitors have an intrinsically stronger preference for highly productive habitat patches than poor competitors. This leads to an equilibrium distribution where the average competitive ability on a patch is strongly correlated with the productivity of the patch. In the second part of our study, we consider what happens if differences in competitive ability are heritable and, hence, subject to natural selection. Under constant environmental conditions, selection eliminates such differences: a single strategy prevails that optimally balances the costs and benefits associated with competitive ability. If the productivity of patches changes during the lifetime of individuals, the spatial assortment of competitors of equal competitive ability gives poor competitors a systematic advantage in times of environmental change, while good competitors benefit from equilibrium conditions. Using evolutionary individual-based simulations, we demonstrate that environmental change may then lead to the diversification of competitive ability. • Strong and weak competitors differ systematically in their habitat preferences. • This leads to the spatial assortment of individuals of similar competitive abilities. • In stable environments, selection removes heritable differences in competitiveness. • Fluctuating environments lead to the coexistence of strong and weak competitors. • Weak competitors can persist as they flourish in periods of environmental change. [ABSTRACT FROM AUTHOR]

In mate choice, social learning may take the form of mate choice copying or anticopying, whereby observed mating decisions are either mimicked or avoided. Alternatively, independent mating decisions may be based on innate preferences or early life social learning. While mate choice copying is widespread among some animal taxa, research in arthropods is limited and results are mixed. We tested these hypotheses using Enchenopa treehoppers (Hemiptera: Membracidae). Enchenopa males produce plant-borne vibrational advertisement signals and females express their mate preferences by selectively duetting with males. Individuals on the plant can monitor these public signals during pair formation. We randomly assigned females to treatment duets consisting of either unattractive or attractive male signals, followed by a long female treatment response (enthusiastic), a short female treatment response (reserved) or no female treatment response. We described the test females' mating preferences before and after the treatment duet. We found that female mate preferences were not affected by the treatment duets. Instead, females had consistent individual differences, which supports the independent mate choice hypothesis and rejects both social learning hypotheses. Our findings suggest that independent mate choice does not necessarily represent a lack of opportunity for social influences from the immediate social context of mate choice. • Pair formation in Enchenopa treehoppers involves male–female signal duets. • These duets provide information about the mating decisions of nearby individuals. • We tested for mate choice copying in Enchenopa with duet playback treatments. • Enchenopa mate preferences were unaffected by the playbacks. • No copying may represent selection for fixed preferences, instead of no opportunity. [ABSTRACT FROM AUTHOR]

The accurate identification of mucinous pancreatic cystic lesions (PCLs) is paramount for cancer risk stratification. Cyst fluid carcinoembryonic antigen (CEA), the only routinely used test, requires high volumes and has low sensitivity. We aimed to compare the performance of two investigational small-volume biomarkers, glucose and the protease gastricsin, to CEA for PCL classification. We obtained cyst fluid samples from 81 patients with pathologically confirmed PCLs from four institutions between 2003 and 2016. Gastricsin activity was measured using an internally quenched fluorescent substrate. Glucose levels were measured with a standard glucometer. CEA levels were obtained from the medical record. Models using Classification and Regression Trees were created to predict mucinous status. Model performance was evaluated using nested cross-validation. Gastricsin activity, CEA, and glucose levels from patients with mucinous (n = 50) and nonmucinous (n = 31) PCLs were analyzed. Area under the curve (AUC) was similar for individual classifiers (gastricsin volume normalized [GVN] 0.88; gastricsin protein concentration normalized [GPN] 0.95; glucose 0.83; CEA 0.84). The combination of two classifiers did not significantly improve AUC, with CEA + GVN (0.88) performing similarly to CEA + GPN (0.95), GVN + glucose (0.87), GPN + glucose (0.95), and CEA + glucose (0.84). The three-analyte combination performed similarly to single and dual classifiers (GPN + glucose + CEA AUC 0.95; GVN + glucose + CEA AUC 0.87). After multiple comparison corrections, there were no significant differences between the individual, dual, and triple classifiers. Gastricsin and glucose performed similarly to CEA and required <5% of the volume required for CEA; these classifiers may be useful in patients with limited cyst fluid. Future multicenter prospective studies are needed to validate and compare these novel small-volume biomarkers. [ABSTRACT FROM AUTHOR]

The patterning of interactions between individuals over time form the foundation for relationships, which are the basis for social group structure. The emergent social structure scaling from interactions might, therefore, be influenced by individual differences in how individuals respond to stressors and uncertainty, which are often intrinsic aspects of social dynamics. During a 17-month study of wild olive baboons, Papio anubis , in Laikipia, Kenya, we measured individual differences in coping style and stress reactivity by experimentally presenting a stressor with multiple solutions. We measured individual differences in sociality through focal animal and ad libitum sampling that recorded grooming, aggression, proximity, and social displacements. We examined whether experimental measures of coping style and stress reactivity (1) are linked to social network assortativity, (2) predict network position and (3) covary with social dominance rank. Homophily was observed for coping styles in a strong proximity network but not when weak associations were included in the analysis. Coping style scores did not predict social network strength or degree. Partner stability indices of proximity associations and social dominance rank did not covary with coping style measures. Static summative network structures may obfuscate investigative inquiries into the role of individual differences and, also, social structure may constrain or facilitate the behavioural expression of such differences. Thus, we should prioritize more fine-grain investigative approaches inclusive of variation in situation, context and consistency of group structure. [ABSTRACT FROM AUTHOR]

Individuals respond adaptively to their environment. Yet, they may differ in their responses even when confronted with the same environmental challenge. Several complementary conceptual frameworks suggest that within populations among-individual variation in life history strategies aligns not only with individuals' propensities to take risks across different situations but also with their sensitivity to variation in environmental cues. Risk-prone individuals, suggested to invest more in current reproduction at the cost of their future reproductive prospects, are predicted to be less sensitive to environmental variation than risk-averse individuals. We tested this prediction in a population of breeding blue tits, Cyanistes caeruleus , by confronting them with different levels of predation threat at their nests and recording their latency to resume brood provisioning after the removal of the predator stimulus. We presented taxidermic woodpecker, Dendrocopos major (a common brood predator) and sparrowhawk, Accipiter nisus (a common adult predator) mounts at each nest, respectively representing low and high levels of threat to adult blue tits. As a nonpredator control stimulus, we presented a blackbird, Turdus merula , mount. We found that on average parents took longer to resume provisioning after presentation of a sparrowhawk than a woodpecker or blackbird. Furthermore, individual latency responses across all threat levels taken together were repeatable. However, despite the population level plastic adjustment to the level of predation threat, we found no evidence for among-individual variation in plasticity. Instead, individual differences in responses were roughly maintained across all levels of threat. While our findings show that individuals differ in their level of risk taking, in the high-stakes and ecologically relevant context of predation risk during parental care, commonly held expectations about among-individual variation in behavioural plasticity were not met. • Individuals are predicted to differ in their adjustment to risky situations. • Breeding blue tits adjust their risk-taking responses to predation threat levels. • Risk taking was repeatable within and across levels of threat. • Individuals did not differ in their plastic adjustment to varying threat levels. [ABSTRACT FROM AUTHOR]

For small, arboreal marmoset monkeys, antipredator vigilance is essential to ensure survival. However, since antipredator vigilance is incompatible with some other behaviours, such as feeding in a head-down position, it has to be regulated efficiently within individuals and perhaps even at the group level. To investigate what drives individual differences in vigilance and feeding behaviour in common marmosets, Callithrix jacchus , and whether they adjust these behaviours to each other, we collected behavioural data on 14 marmosets in contexts where feeding and vigilance were mutually exclusive. The presence of infants resulted in higher overall vigilance and less feeding. Moreover, individuals increased their vigilance when the pair mate was feeding and thus could not be vigilant itself. They thus adjusted their own vigilance to the risk level of their pair mate, which resulted in a turn taking-like pattern of feeding and being vigilant in the pair. This flexibility of vigilance is consistent with marmosets' sensitivity to other's needs in another context, food sharing, when sharing is increased when food is more difficult to obtain. Together, these results suggest considerable awareness of the current state of group members in common marmosets. • Marmosets increased their vigilance when the partner was feeding head down. • This resulted in a turn-taking-like pattern of feeding and being vigilant. • Adults increased their vigilance and decreased feeding when infants were present. • Marmoset vigilance is flexible and takes others' risk level into account. [ABSTRACT FROM AUTHOR]

Behavioural studies have shown that even after accounting for individual differences in contextual and temporal plasticity, considerable unexplained (residual) variation remains. Recent studies show that individuals differ in the magnitude of residual variation (= their predictability), but hardly any studies exist that assess whether this individual attribute itself is repeatable and potentially subject to selection, and whether predictability is related to aspects of different underlying state variables. Using data on the latency to emerge after disturbance of 100 pill bugs, Armadillidium vulgare , measured 24 times each over time and across contexts, we found substantial among-individual variation in mean boldness (latency) and in their behavioural predictability. Individual mean boldness across weeks was highly consistent over time, as was individual predictability; by contrast, unadjusted repeatability of boldness scores (the familiar 'intraclass correlation') and repeatability adjusted for time-related behavioural changes were low to moderate, indicating substantial residual variation. Individual mean boldness was not related to individual predictability, indicating that while selection can potentially act on individual means and individual variances, correlated selection is unlikely, for the traits assessed. Neither boldness nor predictability in boldness was related to mass or to sex, nor did they vary over time concurrent with gains in mass under ad libitum food conditions and in experience with the behavioural assay, indicating they were not clearly related to these potentially important life history and state variables. • Few studies assess repeatability of individual predictability (residual variance). • We report moderate repeatability of predictability in Armadillidium vulgare. • Repeatability suggests predictability is potentially a trait, subject to selection. • Individual predictability was neither linked to personality nor state dependent. • Our evidence supports predictability as a distinct form of behavioural plasticity. [ABSTRACT FROM AUTHOR]

Animal personality results from a complex interplay between consistent individual differences in behaviour and behavioural plasticity in response to environmental variation and can have significant impacts on intraspecific interactions. Littoraria irrorata , the marsh periwinkle, is an important consumer in salt marsh ecosystems and can directly influence marsh health, primarily through its interaction with its main predator, the blue crab, Callinectes sapidus. Here we examine the roles of behavioural type, plasticity and predictability in shaping the antipredator responses of L. irrorata across environmental contexts (i.e. with and without a predator cue). Specifically, we examine changes in measures of boldness: climbing height and time out of refuge, as well as their association with shell morphology. We found that snails exhibited different behavioural types along a bold–shy continuum and that they were correlated across traits. Snails also differed in the shape of their reaction norm and their degree of predictability, both of which were correlated with behavioural type: shy snails climbed higher, spent more time in the refuge and were less plastic and more predictable. Although shell length and size class did not influence snail behaviour, aperture size was strongly linked to key aspects of snail personality, as snails with larger apertures were less bold, less plastic and more predictable. Personality thus appears to be related to certain features of shell morphology and is consistent with phenotypic compensation, where individuals invest in more pronounced morphological defences to compensate for a riskier lifestyle. Given that personality can often determine an individual's growth, development and probability of predation, understanding its role in various ecological contexts, such as population dynamics and predator–prey relationships, is critical. • Littoraria irrorata exhibited consistent individual differences in boldness. • Snails with larger apertures were less bold, less plastic and more predictable. • Size-dependent plasticity may reflect phenotypic compensation for risky behaviour. • Personality may affect salt marsh health via predator–prey interactions. [ABSTRACT FROM AUTHOR]

In many species, individual animals often maintain relatively consistent individual differences in behaviour, indicative of temperament or personality. These stable individual differences are important for life history, survival and health consequences, and the field has seen exponential growth in temperament (e.g. boldness, exploration, sociability, aggression and activity) research. Quantification of animal temperament can be difficult because it requires (1) repeated behavioural measures from the same individual (to gauge within-individual consistency across time and contexts) and (2) identification of the most appropriate behaviour(s) to characterize temperament. In the current study, we took an atheoretical approach and conducted repeat, diverse behavioural tests in a low-variable environment to determine behaviours that were individually consistent over time and across conditions. To control environmental effects on behaviour, we conducted this work with individually housed outbred male Sprague–Dawley rats in a laboratory. To determine individual consistency, we measured each rat's behavioural response to five different arenas (i.e. different contexts) and repeated the five tests at three time points. To identify potential composite, multibehaviour estimates of temperament, we used factor analyses to determine behaviours that covaried on each test arena, and calculated factor scores. To determine individual consistency of behaviours and factor scores across time and contexts, we used reliability and correlation analyses. Several behaviours consistently covaried on each test, and with a few notable exceptions, the resulting factors tended to align with five commonly studied temperament categories. Certain behaviours/factors were more consistent across time and contexts than others; distance travelled/activity were highly consistent, as were sociality- and boldness-related behaviours, whereas aggression and exploration were less consistent. We did not find strong evidence that multibehaviour estimates of temperament (factor scores) were more consistent over time or across conditions than single-behaviour metrics. Where possible, similar atheoretical approaches to cross-time and cross-context behaviour testing will be beneficial for initial temperament characterization. • We quantified behavioural traits in male laboratory rats in low-variable conditions. • Male behaviour was tested on five different arenas, each repeated three times. • Multibehaviour factors scores were no more consistent than single behaviours. • Activity and social boldness were consistent across time and across contexts. [ABSTRACT FROM AUTHOR]

• We evaluated stability of peripheral inflammatory biomarkers in healthy individuals. • Single measures of CRP, IL-6, TNF-α show strong stability up to 6 months. • Over periods >6 months, repeated measures of inflammatory biomarkers are indicated. • Fibrinogen may have moderate stability over periods >3 years. • Inflammatory biomarker stability is similar to blood pressure and lipids. Peripheral immune markers are widely used to predict risk for inflammatory disease. However, whether single assessments of inflammatory biomarkers represent stable individual differences remains unclear. We reviewed 50 studies (N = 48,674; 57 % male; mean age 54 (range 13–79) years) that assessed markers of inflammation on >1 occasion, with time between measures ranging from 24 h to 7+ years. Separate random effects meta -analyses were conducted for each inflammatory marker and time interval. Markers that had broad coverage across most time intervals included C-reactive protein (CRP; k = 37), interleukin (IL)-6 (k = 22), TNF-α (k = 10), and fibrinogen (Fg; k = 9). For CRP, IL-6, and TNF-α, stability estimates generally decreased with time, with strong to moderate stability over intervals <6 months (r's = 0.80-0.61), modest to moderate stability over 6 months – 3 years (r's = 0.60-0.51), and low stability for >3 years (r's = 0.39-0.30). Estimates were less reliable for Fg for time intervals ≤ 3 years although they generally followed the same pattern; more reliable findings suggested greater stability for Fg than other markers for intervals >3 years (r = 0.53). These findings suggest that single measures of inflammatory biomarkers may be an adequate index of stable individual differences in the short term (<6 months), with repeated measures of inflammatory biomarkers recommended over intervals ≥ 6 months to 3 years, and absolutely necessary over intervals >3 years to reliably identify stable individual differences in health risk. These findings are consistent with stability estimates and clinical recommendations for repeated measurement of other cardiovascular measures of risk (e.g., blood lipids, blood pressure). [ABSTRACT FROM AUTHOR]

Strong-aroma Baijiu is a beloved drink in China because of its elegant cellar aroma, sweetness and mellow taste, and its sales account for more than half of the Baijiu production. In this study, three different grades of strong-aroma Baijiu were analyzed systematically using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry coupled with molecular sensory science. A total of 342 aroma compounds were identified in the three samples, including 152 aroma-active compounds. Principal component analysis revealed that higher-grade Baijiu contained more terpenes, acetals, and esters. In contrast, lower-grade Baijiu contained fewer esters and many compounds likely generated by the Maillard reaction, such as 5-methylfurfural, 2-propanoylfuran, 2,6-dimethylpyrazine, and 5-ethyl-2(5 H)-furanone. Most of the aroma attributes of Baijiu samples could be simulated through aroma recombination experiments, but there were still some slight differences in individual aromas. Finally, the key aroma compounds of the three different grades of Baijiu were revealed through omission experiments. This study provided a scientific basis for the classification of strong-aroma Baijiu quality grades, thereby contributing to the high-quality development of the Baijiu industry. • Sensory attributes and key aroma compounds in strong-aroma Baijiu were identified. • Esters played an important role in the different grades of strong-aroma Baijiu. • Profiles of the three different grades of strong-aroma Baijiu were reconstructed. • Ethyl hexanoate, hexanoic acid, ethyl acetate, and ethyl pentanoate are key odorants. [ABSTRACT FROM AUTHOR]

• Age 4 patterning was a unique predictor of children's geometry knowledge at age 5. • Age 4 approximate number system was a unique predictor of age 5 geometry knowledge. • Age 4 patterning was a unique predictor of age 5 numeracy. • Age 4 approximate number system did not relate to age 5 numeracy. Preschoolers' mathematics knowledge develops early and varies substantially. The current study focused on two ontogenetically early emerging cognitive skills that may be important predictors of later math skills (i.e., geometry and numeracy): children's understanding of abstract relations between objects and quantities as evidenced by their patterning skills and the approximate number system (ANS). Children's patterning skills, the ANS, numeracy, geometry, nonverbal intelligence (IQ), and executive functioning (EF) skills were assessed at age 4 years, and their numeracy and geometry knowledge was assessed again a year later at age 5 (N = 113). Above and beyond children's initial knowledge in numeracy and geometry, as well as IQ and EF, patterning skills and the ANS at age 4 uniquely predicted children's geometry knowledge at age 5, but only age 4 patterning uniquely predicted age 5 numeracy. Thus, although patterning and the ANS are related, they differentially explain variation in later geometry and numeracy knowledge. Results are discussed in terms of implications for early mathematics theory and research. [ABSTRACT FROM AUTHOR]

Perceivers' ability to use multiple sources of information when forming impressions—including top-down, perceiver-level features, and bottom-up, target-level features—is a hallmark of social cognition. We investigate this primary foundation by examining the role of perceiver-level and target-level variation in perceived racial prototypicality in the U.S. In Study 1 (200 unique faces; 2608 raters), we quantified contributions of perceiver- and target-level effects to perceived racial prototypicality. Perceiver- and target-level contributions varied across racial category (Asian, Black, Latine, Middle Eastern, and Multiracial), with Multiracial and Middle Eastern prototypicality being more perceiver-driven. Although several appearance features (e.g., perceived ambiguity, skin tone) related to perceived prototypicality, there were distinctions in how perceivers used them (e.g., some people strongly used skin tone to infer Black prototypicality, while others used this less or not at all). A second study (N = 511) experimentally manipulated race essentialist beliefs. While there was no impact on perceived racial prototypicality, regardless of the category (Asian, Black, Latine, Middle Eastern, Multiracial, and Native American), Middle Eastern, Multiracial, and Native American prototypicality were generally more perceiver-driven than other categories, converging with Study 1. Further, perceivers' social dominance orientation, but not several other individual differences, were associated with less use of each of these categories. Taken together, findings suggest perceived racial prototypicality may originate less from stable individual differences like attitudes and instead reflects both i) differences in perceptions of target features and ii) differences in how people use particular target features in making racial prototypicality judgments. [ABSTRACT FROM AUTHOR]

How strongly do higher investment premiums tempt people to invest in unethical assets, such as harmful 'sin stocks'? We present two experimental studies (N total = 1260) examining baseline willingness to invest in 'sin stocks' (without a premium), changes in investments as premiums increase, and how individual differences in deontological and utilitarian inclinations and dark personality traits impact baseline and changes to investments. We compare results to hypothetical models of sensitivity to higher returns: a) full resilience (to moral decay), where people increase investment in regular but not sin stocks with increasing premiums, b) partial resilience, where increasing premiums increases investment more slowly for sin than regular stocks, c) sin deduction: a flat baseline penalty for sin versus regular stocks resulting in similar sensitivity to increasing premiums, and d) decay, where investment differences in sin versus regular stocks reduce as premiums increase. On average, responses aligned best with the partial resilience model. Individual differences in morally-relevant traits moderated effects: most notably, people with higher deontological inclinations and lower dark traits showed greater resilience. However, 21–33% of participants exhibited full resilience, refusing to invest more in sin stocks even as premiums increased, which was more common in people with higher deontological inclinations and lower dark traits. These findings suggest that decisions to invest in sin stocks reflect the sensitivity to the sinfulness of the stock, which remains strong even after unethical investments are made more attractive. We conclude that increasing the economic reward of unethical investments does not crowd out moral concerns. [ABSTRACT FROM AUTHOR]

Individual differences in electrical impedance spectroscopy (EIS) parameters is a technical bottleneck in fruit quality detection. To achieve non-destructive fruit quality testing and minimize the impact of individual differences, this paper proposes a frequency selection + support vector machine strategy based on the frequency response characteristics of biological tissues and the path of current flow. This study found obvious differences in the EIS parameters of different samples. The measurement stability was affected by the electrode type and frequency. The destructive needle electrode was much less affected by individual differences than the non-destructive patch electrode. The effect of low frequencies was greater than that of high frequencies. The heterogeneity of the fruit peel and pulp and the contact area between the electrode and peel were the main reasons for individual differences. When detecting banana maturity, the highest precision of the models was 98.9% by proposed methods; however, the generalizability of the model and its application for other fruit quality tests still require further verification and optimization. The results promote the practical application of EIS in the field of fruit quality assessment and provide new insights for the quality evaluation of other agricultural products. • Measurement stability of needle is superior to patch electrodes. • Heterogeneity of cell tissue and uneven electrode area results differences in EIS. • Frequency selection + SVM method can reduce the impact of individual differences. [ABSTRACT FROM AUTHOR]

• Left-lateralized occipito-frontal functional connectivity correlated with individual Braille reading proficiency. • Increased bidirectional LOC-IFC information flow with predominant top-down communication emerged in a natural Braille reading task. • Greater top-down modulation contributed to higher Braille reading proficiency. • A 'two-tale' model of the LOC-IFC neural link better predicts individual differences in natural Braille reading among late blind people. Natural Braille reading presents significant challenges to the brain networks of late blind individuals, yet its underlying neural mechanisms remain largely unexplored. Using natural Braille texts in behavioral assessments and functional MRI, we sought to pinpoint the neural pathway and information flow crucial for Braille reading performance in late blind individuals. In the resting state, we discovered a unique neural connection between the higher-order 'visual' cortex, the lateral occipital cortex (LOC), and the inferior frontal cortex (IFC) in late blind individuals, but not in sighted controls. The left-lateralized LOC-IFC connectivity was correlated with individual Braille reading proficiency. Prolonged Braille reading practice led to increased strength of this connectivity. During a natural Braille reading task, bidirectional information flow between the LOC and the IFC was positively modulated, with a predominantly stronger top-down modulation from the IFC to the LOC. This stronger top-down modulation contributed to higher Braille reading proficiency. We thus proposed a two-predictor multiple regression model to predict individual Braille reading proficiency, incorporating both static connectivity and dynamic top-down communication between the LOC-IFC link. This work highlights the dual contributions of the occipito-frontal neural pathway and top-down cognitive strategy to superior natural Braille reading performance, offering guidance for training late blind individuals. [ABSTRACT FROM AUTHOR]

• We characterized white matter microstructure in childhood procedural learning using FBA. • Fiber density of cerebellar tracts was related to procedural learning on the SRT task. • This relationship mirrors what we have previously observed in adults. In adults, individual differences in procedural learning (PL) are associated with white matter organization within the basal ganglia-cerebellar circuit. However, no research has examined whether this circuitry is related to individual differences in PL during childhood. Here, 28 children (M age = 10.00 ± 2.31, 10 female) completed the serial reaction time (SRT) task to measure PL, and underwent structural magnetic resonance imaging (MRI). Fixel-Based Analysis was performed to extract specific measures of white matter fiber density (FD) and fiber cross-section (FC) from the superior cerebellar peduncles (SCP) and the striatal premotor tracts (STPMT), which underlie the fronto-basal ganglia-cerebellar system. These fixel metrics were correlated with the 'rebound effect' from the SRT task – a measure of PL proficiency which compares reaction times associated with generating a sequence, to random trials. While no significant associations were observed at the fixel level, a significant positive association was observed between average FD in the right SCP and the rebound effect, with a similar trend observed in the left SCP. No significant effects were detected in the STPMT. Our results indicate that, like in adults, microstructure of the basal ganglia-cerebellar circuit may explain individual differences in childhood PL. [ABSTRACT FROM AUTHOR]

• The single-trial ERP-behavioral correlation approach was applied to show how the ERP was associated with behavior. Accumulated functional magnetic resonance imaging (fMRI) and electroencephalography evidence indicate that numerosity is first processed in the occipito-parietal cortex. fMRI evidence also indicates right-lateralized processing of numerosity, but there is no consistent evidence from event-related potential (ERP) studies. This study investigated the ERP of numerosity processing in the left, right, and bilateral visual fields. The single-trial ERP-behavioral correlation was applied to show how the ERP was associated with behavioral responses. The results showed a significant early behavioral-ERP correlation on the right N1 component when stimuli were presented in the left visual field rather than in the right visual field. The behavioral ERP correlation was termed BN1. There was bilateral BN1 based on the reaction time or error rate, but the right BN1 was larger than that the left BN1 when the stimulus was present in the bilateral visual field. Therefore, this study provided a new neural marker for individual differences in processing numerosity and suggested that processing numerosity was supported by the right occipito-parietal cortex. [ABSTRACT FROM AUTHOR]

• Emphasizes relatively underexplored semantic contributions of word-level features. • Item-level familiarity increased the likelihood that a word was read correctly. • Set for variability, age of acquisition, and morphemes were significant predictors. • The effect of age of acquisition varies across word reading efficiency. • Results support the importance of word knowledge for reading polysyllabic words. Across word reading development, there are important and evolving relationships between oral and written semantic knowledge. Recent research has focused on these relationships, with accumulating evidence supporting the role of word knowledge and related word characteristics as important factors influencing polysyllabic word reading abilities. The purpose of this study was to investigate how semantic-related effects across child-level skills (e.g., general vocabulary knowledge), word-level properties (e.g., age of acquisition), child-by-word-level familiarity (e.g., item-level familiarity), and interactions between key child attributes and word characteristics (e.g., word reading skill by age of acquisition) contribute to polysyllabic word reading. Specifically, we emphasize the semantic contributions of word-level features to word reading development, which have been relatively underexplored in the literature. A sample of elementary school students oversampled for word reading difficulty (N = 92) in Grades 3 to 5 read a set of polysyllabic words (J = 45) and completed a battery of reading and language-related measures. Using cross-classified random-effects models and accounting for various control variables, semantic-related variables representing item-level familiarity; child-level set for variability; and word-level age of acquisition and number of morphemes were significant predictors in the main-effects model. A significant interaction between sight word efficiency and age of acquisition indicated higher probabilities of correctly reading polysyllabic words at lower levels of acquisition for better readers. Results indicate important semantic-related influences on polysyllabic word reading at the child, word, and child-by-word levels, suggesting meaningful relationships between knowledge of the orthographic form of a word and semantic knowledge in developing readers. [ABSTRACT FROM AUTHOR]

• Objectively-assessed sleep duration is highly heritable in middle childhood. • Positive parent personality moderated heritability of child sleep duration. • Parental stress and strain moderated heritability of sleep duration in childhood. • Genetic expression of sleep duration may be altered by early-life parental factors. • Parental factors may be central to child sleep health. Early-life positive and adverse parental factors, such as positive parent personality and parental stress, affect the environmental context in which children develop and may influence individual differences in children's sleep health. This study examined the moderating role of early-life parental factors in the heritability (i.e., the extent to which individual differences are due to genetic influences) of objectively assessed childhood sleep duration. A total of 351 families from the Arizona Twin Project were studied. Primary caregivers (95% mothers) reported on multiple dimensions of stress and facets of their own personality when the twins were 12 months old. Seven years later (M age = 8.43 years, SD = 0.68), families completed a home visit, and twins (51% female; 57% White, 29% Hispanic; 30% monozygotic, 39% same-sex dizygotic, 31% other-sex dizygotic) wore actigraph watches to assess their sleep, with caregivers completing similar assessments on their personality attributes and stress. Early-life positive parent personality moderated the heritability of sleep duration (Δ−2LL [−2 log likelihood] = 2.54, Δ df = 2, p =.28), such that as positive parent personality increased, the heritability of duration decreased. Early-life parental stress also moderated the genetic contribution to sleep duration (Δ−2LL = 2.02, Δ df = 2, p =.36), such that as stress increased, the heritability of duration increased. Concurrent positive parent personality and parental stress composites showed similar patterns of findings. Results highlight the likely contribution of parent positive traits and adverse experiences to the etiology of children's sleep health, with genetic influences on children's sleep more prominent in "riskier" environments. Understanding how genetics and environments work together to influence the etiology of sleep may inform prevention programs. [ABSTRACT FROM AUTHOR]

• Free word generation can be used as a proxy for the stream of thought. • The heightened variability of spontaneous thought associated with ADHD is also present in the general population as a continuum. • Stream of thought dynamics is linked to a general tendency for exploration. For a long time, clinical knowledge and first-person reports have pointed to individual differences in the dynamics of spontaneous thoughts, in particular in the extreme case of psychiatric conditions (e.g. racing thoughts in Attention Deficit / Hyperactivity Disorder, ADHD; rumination in depression). We used a novel procedure to investigate this individual variability by combining verbal fluency tasks and introspective reports of thought content. Our goal was twofold. First, we tested the hypothesis that a greater segmentation of the stream of thoughts would be associated with trait inattention, in line with subjective reports of ADHD patients. Second, we tested whether the segmentation of the stream of thoughts increased with an increased tendency for exploratory behavior, following recent theoretical claims on the mechanisms underpinning the generation of spontaneous thoughts. Our results support both hypotheses, shedding light on the factors contributing to the individual variability in the dynamics of the stream of thought. [ABSTRACT FROM AUTHOR]

• We examine new aspects of children's ordinal understanding of a number line. • We measure if children place numbers correctly relative to each other and benchmarks. • Our new measures may reflect unique aspects of children's ordinal understanding. • Children with fewer rather than more ordinal errors scored higher on math ability. • Children with fewer vs. more ordinal errors made larger estimation gains (lower PAE). Children's performance on the number line estimation task, often measured by the percentage of absolute error, predicts their later mathematics achievement. This task may also reveal (a) children's ordinal understanding of the target numbers in relation to each other and the benchmarks (e.g., endpoints, midpoint) and (b) the ordinal skills that are a necessary precursor to children's ability to understand the interval nature of a number line as measured by percentage of absolute error. Using data from 104 U.S. kindergartners, we measured whether children's estimates were correctly sequenced across trials and correctly positioned relative to given benchmarks within trials at two time points. For both time points, we found that each ordinal error measure revealed a distinct pattern of data distribution, providing opportunities to tap into different aspects of children's ordinal understanding. Furthermore, children who made fewer ordinal errors scored higher on the Test of Early Mathematics Ability and showed greater improvement on their interval understanding of numbers as reflected by a larger reduction of percentage of absolute error from Time 1 to Time 2. The findings suggest that our number line measures reveal individual differences in children's ordinal understanding of numbers, and that such understanding may be a precursor to their interval understanding and later mathematics performance. [ABSTRACT FROM AUTHOR]

Limited evidence is available about the variability of appetitive responses within individuals after an acute bout of exercise. The present study aimed to assess the consistency and individual variability of post-exercise appetitive responses in healthy individuals. Twenty participants (10 females, 23.9 ± 4.1 years, 22.5 ± 2.0 kg m−2) joined the laboratory to perform four sessions separated by a minimum of 5 days: i) a control session with a rest period before and an ad libitum lunch (REST), and ii) three identical exercise sessions (EX) with a 30-min moderate-intensity (60–70% of predicted maximal heart rate) walking bout ending 25 min before the ad libitum lunch. Subjective appetite sensations were assessed before and after the meal at regular intervals, and satiety quotients were calculated. Food reward was assessed by the Leeds Food Preference Questionnaire before and after lunch. For each EX session, the difference with the REST session was calculated (Δ = EX – REST). Energy and macronutrient intake were consistent in response to exercise (all intraclass correlation coefficients (ICC) > 0.8) while results showed that post-exercise subjective appetite sensations and satiety quotients varied across the three EX sessions (almost all ICC < 0.7). Food reward was overall consistent in response to exercise before the test meal but not after. When considering the changes (Δ), the results showed no or poor consistency for most of the appetitive outcomes. To conclude, energy and macronutrient intake, as well as pre-meal food reward, are consistent after exercise in healthy individuals, while subjective appetite sensations are not stable within individuals across the sessions. Regarding the variations from REST to EX sessions, the results suggest that the individual changes observed are only random day-to-day variations. [ABSTRACT FROM AUTHOR]

We find that people implicitly and explicitly represent healthy foods they categorize as healthy in their purest, least prepared forms but represent foods they categorize as unhealthy in their most prepared forms (e.g., a veggie patty is represented as frozen while a beef burger is represented in a bun with melted cheese and ready to eat). We find this effect across several studies using both image and word sorting measures in explicit tasks and implicit association tasks. The effect results from the perception of health and taste as two conflicting goals. Preparation (e.g., cooking, adding toppings) makes food more delicious, which creates categorization ambiguity. Hence, healthy food is thought of as unprepared. Indeed, individual differences in perceived health-taste goal conflict moderate the effect. Critically, the representation of healthy foods matters for food decisions. In an experiment that manipulated the descriptive language on a restaurant menu, emphasizing the preparation of foods increased participants' preference for healthy foods (with no improvement for unhealthy foods). [ABSTRACT FROM AUTHOR]

Research has identified forgiveness as one of the most productive forms of resolution following an interpersonal transgression. Despite the benefits of forgiveness, some individuals are more forgiving than are others. Although past work has examined gender differences in forgiveness, less is known about how within-sex individual differences may affect the willingness to forgive. In this paper, we study how masculinity concerns relate to forgiveness in men. We assert that forgiveness is associated with a perceived lack of masculinity and predict that, because of this relationship, men who are more concerned about maintaining their sense of masculinity will be less forgiving following a transgression. Across four studies, we find support for our predictions. In addition, we show how a small intervention in which participants reassert their sense of manhood reduces this effect, making men more willing to forgive. [ABSTRACT FROM AUTHOR]

• Study of the robustness of punishment can reveal additional individual differences. • Punishment resistance is a prerequisite to model abstinence from addiction. • Repeated punishment cycles could be used to model progressive recovery. Continued drug use despite negative consequences is a hallmark of addiction commonly modelled in rodents using punished drug intake. Over the years, addiction research highlighted two subpopulations of punishment sensitive and resistant animals. While helpful to interrogate the neurobiology of drug-related behaviors, these procedures carry some weaknesses that need to be recognized and eventually defused. Mainly focusing on footshock-related work, we will first discuss the criteria used to define punishment-resistant animals and how their relative arbitrariness may impact our findings. With the overarching goal of improving our interpretation of the punishment-resistant phenotype, we will evaluate how tailored punishment protocols may better apprehend resistance to punishment, and how testing the robustness of punishment resistance could yield new results and strengthen interpretations. Second, we will question whether and to what extent punishment sensitivity, as currently defined, is reflective of abstinence and suggest that punishment resistance is, in fact, a prerequisite to model abstinence from addiction. Again, we will examine how challenging the robustness of the punishment-sensitive phenotype may help to better characterize it. Finally, we will evaluate whether diminished relapse-like behavior after repeated punishment-induced abstinence could not only contribute to better understand the mechanisms of abstinence, but also uniquely model progressive recovery (i.e., after repeated failed attempts at recovery) which is the norm in people with addiction. Altogether, by questioning the strengths and weaknesses of our models, we would like to open discussions on the different ways we interpret punishment sensitivity and resistance and the aspects that remain to be explored. [ABSTRACT FROM AUTHOR]

Theories of parallel memory systems suggest that flexible wayfinding (e.g., shortcutting) requires knowledge about the spatial structure of an environment, whereas automatic wayfinding (e.g., route-following) does not. Distal landmarks have widely been assumed to promote learning a spatial representation of an environment and, thus, flexible wayfinding through it. There is, however, little behavioural evidence to corroborate this assumption. In three experiments reported here, participants learned a circuitous route through a large-scale virtual garden maze, after which they completed orientation and wayfinding tests that measured their knowledge of the spatial structure of the environment and ability to shortcut through it, respectively. In Experiment 1, we found no evidence of a benefit to navigation in the presence versus the absence of distal landmarks when participants had continuous experience of the learned route, but pointing accuracy and shortcutting ability decreased when the learned route was complex compared to simple. In Experiment 2, participants learned a simple circuitous route in segments, and we observed superior knowledge of how the separately learned local spaces were aligned in the presence versus the absence of distal landmarks. Across all experiments, consistent with parallel memory systems, we observed that knowledge of the spatial structure of the environment was related to shortcutting but not route-following. This pattern of data suggests that distal landmarks promote the integration of separately learned local spaces into a coherent global representation, but do not promote learning of local spaces beyond what can be achieved by tracking self-motion. • Flexible wayfinding (e.g., shortcutting) requires knowledge of spatial relations. • Route-following does not require knowing the spatial structure of the environment. • Shortcutting, but not route-following, was correlated with pointing judgements. • Distal landmarks did not support learning a spatial representation of local spaces. • Distal cues supported integrating local spaces in a coherent global representation. [ABSTRACT FROM AUTHOR]

Many animal species use vocal and nonvocal acoustic signals to communicate over large distances. Wild chimpanzees, Pan troglodytes , drum on the buttress roots of trees, generating low-frequency sounds that can reach distances of over 1 km. Buttress drumming is produced in bouts of beats and is often accompanied by pant hoots, the species-typical long-distance vocalization. We investigated whether individual differences exist in the acoustic structure of drumming bouts produced by male chimpanzees of the Waibira community in the Budongo Forest in Uganda, and whether individual, contextual and social factors affected their use of drumming. We found individual differences in drumming bouts produced by seven male chimpanzees during travel events as well as in their timing within the pant hoot, and discriminated specific patterns of beats for some chimpanzees. In contrast, we found no evidence for individual differences in the acoustic structure of drumming bouts produced by four males during displays. Together these findings suggest that chimpanzees may be able to choose to encode identity within individual drumming 'signatures'. Chimpanzees drummed less frequently as their party size increased. We found no evidence that the age of the signaller or the presence of preferred social partners, higher-ranking males or females in oestrus affected the use of drumming. These findings suggest there may be flexibility in buttress drumming across social and behavioural contexts and provide support for the hypothesis that, by encoding individual identity, long-distance drumming may be used to facilitate chimpanzee fission–fusion social dynamics. • Chimpanzees produce low-frequency sounds by drumming on buttress roots of trees. • Drumming is used across contexts with apparently long- and short-distance functions. • Chimpanzee drums encode individual signatures in travel events but not in displays. • Patterns of production suggest drumming coordinates fission–fusion dynamics. [ABSTRACT FROM AUTHOR]

Interindividual differences in behaviour within the members of a social group can affect the group's productivity. In eusocial insects, individual differences between workers in a colony play a central role in division of labour and task allocation. Extensive empirical and theoretical work has highlighted variation in response thresholds as a proximate mechanism underlying individual behavioural differences and hence division of labour. However, other response parameters, like response probability and intensity, can also affect these differences. In this study, we first extended a previously published agent-based model on honey bee, Apis mellifera , foraging to understand the relative importance of response (dance) probability and response (dance) intensity in the task of recruitment. Comparing variation obtained from the simulations with previously published empirical data, we found that response intensity played a more important role than probability in producing consistent interindividual differences in recruitment behaviour. We then explored the benefits provided by this individual variation in recruitment behaviour to the colony's collective foraging effort under different environmental conditions. We found that individual variation led to a greater energy yield per forager, but only when food was abundant. Our study highlights the need to consider all response parameters while studying division of labour and adds to the growing body of evidence linking individual variation in behavioural responses to the success of social groups. • A. mellifera foragers show consistent individual differences in recruitment. • Agent-based models were used to explore the role of these differences in the colony. • Empirical findings were reproduced by including response probability and intensity. • Individual variation reduced total recruitment and slightly increased energy yield. • Studies on division of labour should include thresholds, probability, and intensity. [ABSTRACT FROM AUTHOR]

Knowledge of the drivers of fine-scale spatial ecology in wide-ranging marine species is vital to understand population structuring and conserve threatened species. Movements and habitat use are likely to be strongly influenced by social relationships between individuals, and social units within animal populations may be subject to distinct selective pressures. Here we used passive acoustic telemetry and network-based analyses to investigate the site visit patterns and social affiliations of reef manta rays, Mobula alfredi , in Raja Ampat, West Papua. Acoustic transmitters were externally deployed on 27 rays that were tracked for up to 110 days. Visit profiles were retrieved from nine acoustic receivers positioned in clusters at known aggregation sites, enabling analysis of movement behaviour and social processes at various spatial scales. We utilized Bayesian inference and a double permutation method to address issues in sampling and hypothesis testing on social networks constructed from automated telemetry data. We found that social affiliations were assorted into spatially defined communities which remained stable over several weeks to months, although many affiliations were short lived. Interindividual variability in detection profiles was correlated with social network metrics. Individuals with high levels of site attachment had stronger social affiliations, while individuals that regularly attended different receiver clusters were more central to the overall social network. These results suggest that reef manta ray movements, habitat preferences and social relationships should be understood as linked behavioural processes for which variability between individuals and groups may drive emergent population structure. Future research and local management of manta rays will likely benefit from identifying how, where and why social gatherings occur. • We used acoustic telemetry to record fine scale social dynamics in reef manta rays. • Social affiliations were assorted into spatial communities. • Social structuring persisted over time periods of weeks to months. • Individuals with high levels of area fidelity had stronger affiliations. • Mobile individuals were important in connecting social networks. [ABSTRACT FROM AUTHOR]

Cognition is vital for carrying out behaviours required for survival and reproduction. Cognitive performance varies between species, but also between individuals within populations. While variation is a prerequisite for natural selection, selection does not act on traits in isolation. The extent to which cognitive traits covary with other aspects of phenotype (e.g. personality traits) may be important in shaping evolutionary dynamics. Here we adopted a multivariate approach to test spatial learning in male Poecilia reticulata and asked whether differences in cognitive performance are associated with (repeatable) differences in stress response behaviour. Functional links between cognitive traits and 'stress coping style' have been hypothesized. Furthermore, individual level studies of cognitive performance typically rely on multiple testing paradigms that may themselves be a stressor. There is a risk that variation in stress responsiveness is itself a cause of apparent, but artefactual variance in cognitive ability. Fish repeatedly experienced two spatial learning tasks (maze layouts) and an acute stress response test (open field trial). We found repeatable differences between individuals in performance within and across maze layouts. On average, performance improved with experience in the first maze, consistent with spatial learning, but not in the second. Individuals varied in the trajectory of mean performance with trial number in both mazes, suggesting they differ in 'learning rate'. Acute stress response behaviour was repeatable but predicted neither average time to solve the maze nor learning rate. We found no support for between-individual correlation between acute stress response and cognitive performance. However, we highlight the possibility that cumulative, chronic stress effects may nevertheless cause declines in performance for some individuals (leading to lack of improvement in mean time to solve the second maze). If so, this may represent a pervasive but difficult challenge for our ability to robustly estimate learning rates in studies of animal cognition. • Multivariate approach to test spatial learning and acute stress response in guppies. • Spatial learning performance is repeatable among individuals across contexts. • Acute stress response behaviour is also repeatable among individuals. • No support for correlation between acute stress response and cognitive performance. • Cumulative chronic stress may cause declines in performance for some individuals. [ABSTRACT FROM AUTHOR]

• CVA decreases as executive function demands increase. • CVA changes moderate the association of changes in cognitive and prefrontal response. • A larger CVA withdrawal may be adaptive in situations requiring high executive demands. Phasic cardiac vagal activity (CVA), reflecting ongoing, moment-to-moment psychophysiological adaptations to environmental changes, can serve as a predictor of individual difference in executive function, particularly executive performance. However, the relationship between phasic CVA and executive function demands requires further validation because of previous inconsistent findings. Moreover, it remains unclear what types of phasic changes of CVA may be adaptive in response to heightened executive demands. This study used the standard N-back task to induce different levels of working memory (WM) load and combined functional Near-Infrared Spectroscopy (fNIRS) with a multipurpose polygraph to investigate the variations of CVA and its interactions with cognitive and prefrontal responses as executive demands increased in fifty-two healthy young subjects. Our results showed phasic decreases in CVA as WM load increased (t (51) = -3.758, p < 0.001, Cohen's d = 0.526). Furthermore, phasic changes of CVA elicited by increased executive demands moderated the association of cognitive and cerebral hemodynamic variations in the prefrontal cortex (B = 0.038, SE = 0.014, p < 0.05). Specifically, as executive demands increased, individuals with larger phasic CVA withdrawal showed a positive relationship between cognitive and hemodynamic variations in the prefrontal cortex (β = 0.281, p = 0.031). No such significant relationship was observed in individuals with smaller phasic CVA withdrawal. The current findings demonstrate a decrease in CVA with increasing executive demands and provide empirical support for the notion that a larger phasic CVA withdrawal can be considered adaptive in situations requiring high executive function demands. [ABSTRACT FROM AUTHOR]

• The difference in median response time (ΔMRT) between negative faces and neutral shapes can be utilized in quantifying individual differences in the speed of emotional facial discrimination. • Negative faces task condition functional connectivity (FC) predicted individual ΔMRT in healthy adults and adolescents. • Negative faces task condition FC performed better in predicting these individual differences compared to resting-state FC. Every individual experiences negative emotions, such as fear and anger, significantly influencing how external information is perceived and processed. With the gradual rise in brain-behavior relationship studies, analyses investigating individual differences in negative emotion processing and a more objective measure such as the response time (RT) remain unexplored. This study aims to address this gap by establishing that the individual differences in the speed of negative facial emotion discrimination can be predicted from whole-brain functional connectivity when participants were performing a face discrimination task. Employing the connectome predictive modeling (CPM) framework, we demonstrated this in the young healthy adult group from the Human Connectome Project-Young Adults (HCP-YA) dataset and the healthy group of the Boston Adolescent Neuroimaging of Depression and Anxiety (BANDA) dataset. We identified distinct network contributions in the adult and adolescent predictive models. The highest represented brain networks involved in the adult model predictions included representations from the motor, visual association, salience, and medial frontal networks. Conversely, the adolescent predictive models showed substantial contributions from the cerebellum-frontoparietal network interactions. Finally, we observed that despite the successful within-dataset prediction in healthy adults and adolescents, the predictive models failed in the cross-dataset generalization. In conclusion, our study shows that individual differences in the speed of emotional facial discrimination can be predicted in healthy adults and adolescent samples using their functional connectivity during negative facial emotion processing. Future research is needed in the derivation of more generalizable models. [ABSTRACT FROM AUTHOR]

• Parents judged their children's interest level in science and non-science topics. • In general, parents somewhat accurately judged children's interests. • Parents underestimated science interests. • Favorable attitudes toward science positively biased parent judgments. • Parents of older (vs. younger) kids judged non-science interests more accurately. Parents' judgments about their children's level of interest in different science topics may affect the science-learning opportunities they provide their children. However, little is known about how parents judge these interests. We used the truth and bias model of judgment of West and Kenny (Psychological Review [2011], Vol. 118, pp. 357–378) to examine factors that may affect parents' judgments of their children's science interests such as the truth (children's self-reported interest) and potential sources of parental bias. We also investigated whether several individual difference measures moderated the effect of truth or bias on judgments. Children (N = 139, ages 7–11 years) rated their level of interest in five science and five non-science topics. Separately, parents (N = 139) judged their children's interest in the same topics. Overall, parents accurately judged their children's science interests, but we also found evidence of some forms of bias, namely that parents generally under-estimated their children's science interests. In addition, parents' personal science attitudes were related to judgments of science interests, such that parents more favorable of science tended to rate their children's interest in science topics higher than parents with a less favorable view. We did not find evidence that individual differences among parents moderated the effect of truth or bias on judgments; however, parents were more accurate at judging the non-science interests of older children than younger children. Parents should be aware that they may be under-estimating their children's interest in science topics and that their personal attitudes about science may be influencing their judgments of their children's science interests. [ABSTRACT FROM AUTHOR]

• Competition was tested as one possible mechanism for the single-language learning advantage. • Competition in bilingual word learning exists even when language is tagged by a speaker cue. • The one-person one-language input format does not mitigate the single-language advantage. • Bilingual children successfully learn words in both dual- and single-language contexts. • Individual differences in language ability do not moderate differences between dual- and single language learning. This study investigated the role of dual- and single-language input in bilingual children's word learning. In Experiment 1, 26 Spanish–English bilingual children aged 4 and 5 years (9 girls; 73% Latino; 65% White) learned novel words in single- and dual-language conditions. In the single-language condition, children learned English-like labels for novel objects. In the dual-language condition, the same children learned Spanish- and English-like labels for a different set of objects; all labels were produced by the same bilingual speaker, creating competition between the two languages. A second group of bilingual children (N = 25; 14 girls; 72% Latino; 40% White) participated in Experiment 2, which tested whether tagging language by speaker in the dual-language condition (mimicking the one person–one language input strategy) would influence performance. In both experiments, participants learned novel English words above chance (p s <.05) in both conditions, with better performance in the single-language condition. These results indicate an advantage for single-language learning contexts, but the theoretical roots and the practical value of this advantage are unclear. [ABSTRACT FROM AUTHOR]

Psychosocial stress is a key predictor of adverse mental and physical health outcomes. Yet, the field of stress science has been limited by insufficient consideration of individual differences, particularly personality, as well as imprecise definitions and assessment of stress. The focus of this special issue is on personality associations with stress risk and resilience, including the potential mechanisms underlying these associations. [ABSTRACT FROM AUTHOR]

• Extraversion predicts more positive attitudes towards everyday social touch. • Attachment avoidance and anxiety are stronger predictors of intimate touch. • Interoceptive accuracy and body image only weakly predict touch outcomes. • Results were obtained from a large and diverse UK healthy adult sample. • Highlights the interplay between perceiver and context in shaping touch perception. Attitudes and experiences of touch vary considerably between individuals and also shift in response to societal change. This preregistered study examined predictors of inter-individual variability in touch attitudes and experiences in a large and diverse UK healthy adult sample (N = 15,166). Trait extraversion was the strongest predictor of day-to-day social touch attitudes (e.g., handshakes), where greater extraversion predicted more positive attitudes. Attachment avoidance and anxiety most strongly predicted attitudes and experiences of intimate touch (e.g., kissing, caressing). This study is the first to analyse the relative contribution of individual difference predictors to this broad range of touch attitudes and experiences. Findings highlight the complex interplay between perceiver and context in shaping touch experiences. [ABSTRACT FROM AUTHOR]

Testosterone production in women is thought to systematically shift across the menstrual cycle, peaking during the mid-cycle ovulatory window, and potentially influencing women's behavior. Testosterone is a molecular intermediary to the production of estradiol, which is necessary for ovulation to occur, but the amount of testosterone escape and exposure to the peripheral tissues is not fully understood. Salivary testosterone is a common biomarker in behavioral neuroendocrinological studies and is thought to reflect the bioactive portions in serum. In N = 339 women with confirmed ovulation via luteinizing hormone tests, salivary testosterone, assayed with LC-MS/MS, was sampled four times across the mid-cycle ovulatory window the luteal phase. Within-subject analysis revealed a significant but small pattern of a mid-cycle peak and a luteal decrease at the aggregate level. However, at the individual level, there was substantial variability in the direction and magnitude of the testosterone-cycle pattern. We discuss the relevant underlying physiology, background research, issues with assay methodolody, and considerations for researchers studying testosterone levels in women. • Salivary testosterone across the menstrual cycle was assessed with LC-MS/MS • Within-subject analyses show a slight trend towards a mid-cycle peak and luteal decrease at the aggregate level • There were considerable individual differences in the direction and magnitude of change • Menstrual patterns of testosterone appear subtle and not systematic across individuals [ABSTRACT FROM AUTHOR]