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Circadian clocks are inherent to most organisms, including cryptozoic animals that seldom encounter direct light, and regulate their daily activity cycles. A conserved suite of clock genes underpins these rhythms. In this study, we explore the circadian behaviors of the red flour beetle Tribolium castaneum, a significant pest impacting stored grain globally. We report on how daily light and temperature cues synchronize distinct activity patterns in these beetles, characterized by reduced morning activity and increased evening activity, anticipating the respective environmental transitions. Although less robust, rhythmicity in locomotor activity is maintained in constant dark and constant light conditions. Notably, we observed more robust rhythmic behaviors in males than females with individual variation exceeding those previously reported for other insect species. RNA interference targeting the Clock gene weakened locomotor activity rhythms. Our findings demonstrate the existence of a circadian clock and of clock-controlled behaviors in T. castaneum. Furthermore, they highlight substantial individual differences in circadian activity, laying the groundwork for future research on the relevance of individual variation in circadian rhythms in an ecological and evolutionary context. [ABSTRACT FROM AUTHOR]

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ13C and δ15N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within‐individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations. [ABSTRACT FROM AUTHOR]

A number of papers have applied the CNI model of moral judgments to investigate deontological and consequentialist response tendencies. A controversy has emerged concerning the methodological assumptions of the CNI model. In this article, we contribute to this debate by extending the CNI paradigm with a skip option. This allows us to test an invariance assumption that the CNI model shares with prominent process-dissociation models in cognitive and social psychology. Like for these models, the present experiments found violations of the invariance assumption for the CNI model. In Experiment 2, we replicate these results and selectively influence the new parameter for the skip option. In addition, structural equation modeling reveals that previous findings for the relationship between gender and the CNI parameters are completely mediated by the association of gender with primary psychopathy. [ABSTRACT FROM AUTHOR]

Individual variations in peripheral oxygen saturation (SpO2) during repeated sprints in hypoxia and their impact on exercise performance remain unclear despite fixed external hypoxic stimuli (inspired oxygen fraction: FiO2). This study examined SpO2 individual variations during repeated sprints in hypoxia and their impact on exercise performance. Thirteen highly-trained sprint runners performed 10 × 10-s cycle sprints with 30-s passive recoveries in normobaric hypoxia (FiO2: 0.150). Mean power output (MPO), post-sprint SpO2, and heart rate for each sprint were assessed. Sprint decrement score (Sdec), evaluating fatigue development, was calculated using MPO variables. Participants were categorized into a high saturation group (HiSat, n =7) or a low saturation group (LowSat, n = 6) based on their mean post-sprint SpO2 (measured 10-15 s after each sprint). Individual mean post-sprint SpO2 ranged from 91.6% to 82.2%. Mean post-sprint SpO2 was significantly higher (P < 0.001, d = 1.54) in HiSat (89.1% ± 1.5%) than LowSat (84.7% ± 1.6%). A significantly larger decrease in Sdec (P = 0.008, d = 1.68) occurred in LowSat (-22.3% ± 2.3%) compared to HiSat (-17.9% ± 2.5%). MPO (P = 0.342 d = 0.55) and heart rate (P = 0.225 d = 0.67) did not differ between groups. There was a significant correlation (r = 0.61; P = 0.028) between SpO2 and Sdec. In highlytrained sprint runners, individual responses to hypoxia varied widely and significantly affected repeated sprint ability, with greater decreases in SpO2 associated with larger performance alterations (i.e., larger decrease in Sdec). [ABSTRACT FROM AUTHOR]

Avian nest design varies depending on environmental factors but may also be influenced by between‐species interactions. In the brood parasitism context, hosts may evolve nest architectures that may limit parasite access to the nest cup, reduce parasite laying success or hinder parasite chick success. Therefore, nest characteristics may reduce the likelihood or minimise the costs of being parasitised. The common redstart Phoenicurus phoenicurus is a regular host of the common cuckoo Cuculus canorus, for which cuckoo eggs are often laid outside the nest cup, resulting in low effective parasitism rates. This allowed us to evaluate variation in host nest design and test whether nest design characteristics correlate with brood parasitism likelihood and cuckoo laying success (i.e. cuckoo egg laid in the nest cup versus outside the nest cup). While recording brood parasitism events in two distant redstart populations, we documented nest cup characteristics, such as internal dimensions, materials used and nest cup position, along with the nest‐box dimensions. Cuckoo parasitism likelihood was lower for redstart nests in cavities with smaller entrances, for redstart nests with smaller nest cups and with nest cups that were built level to the rim material. For parasitised nests, cuckoo laying success was lower at redstart nests with nest cups placed further from the cavity entrance. Our results suggest a conditional process, where the cavity entrance size first prevents brood parasites access, then the cup size and the cup level in reference to the rim material affect the cuckoo choice, and finally, the nest cup position hinders cuckoo's laying success. The use of multiple nest design strategies may explain the current low effective parasitism rates in this system. Host nest design may serve as a frontline defence that could shape parasite's preferences, and consequently host nest characteristics. [ABSTRACT FROM AUTHOR]

Ecological networks comprising of mutualistic interactions can suddenly transition to undesirable states, such as collapse, due to small changes in environmental conditions such as a rise in local environmental temperature. However, little is known about the capacity of such interaction networks to adapt to a rise in temperature and the occurrence of critical transitions.Here, combining quantitative genetics and mutualistic dynamics in an eco‐evolutionary framework, we evaluated the stability and resilience of mutualistic networks to critical transitions as environmental temperature increases. Specifically, we modelled the dynamics of an optimum trait that determined the tolerance of species to local environmental temperature as well as to species interaction. We then evaluated the impact of individual trait variation and evolutionary dynamics on the stability of feasible equilibria, the occurrence of threshold temperatures at which community collapses, and the abruptness of such community collapses.We found that mutualistic network architecture, that is the size of the community and the arrangement of species interactions, interacted with evolutionary dynamics to impact the onset of network collapses. Some networks had more capacity to track the rise in temperatures than others and thereby increased the threshold temperature at which the networks collapsed.However, such a result was modulated by the amount of heritable trait variation species exhibited, with high trait variation in the mean optimum phenotypic trait increasing the environmental temperature at which networks collapsed. Furthermore, trait variation not only increased the onset of temperatures at which networks collapsed but also increased the local stability of feasible equilibria.Our study argued that mutualistic network architecture interacts with species evolutionary dynamics and increases the capacity of networks to adapt to changes in temperature and thereby delayed the occurrence of community collapses. [ABSTRACT FROM AUTHOR]

Individual differences in behavior have large consequences for the way in which ecology impacts fitness. Individuals differ in how they explore their environment and how exploratory behavior benefits them. In group-living animals, behavioral heterogeneity can be beneficial because different individuals perform different tasks. For example, exploratory individuals may discover new food sources and recruit group members to exploit the food, while less exploratory individuals forgo the risks of exploration. Here we ask how individual variation in exploratory behavior affects the ability of Argentine ant Linepithema humile colonies to (1) locate novel food sources, (2) exploit known food resources, and (3) respond to disruptions while foraging. To address these questions, we conducted field experiments on L. humile foraging trails in which we manipulated food availability near and at the foraging trails and disrupted the foraging trails. We sampled individuals based on their response to the perturbations in the field and tested their exploratory behavior in the lab. We found that exploratory individuals benefit the colony by locating novel foods and increasing resource exploitation, but they do not play an important role in the recovery of a foraging trail after disruption. Thus, the benefits of behavioral heterogeneity to the group, specifically in exploratory behavior, differ across ecological contexts.

Rhincodon typus, or the whale shark, is the largest extant fish in the world and is classified as endangered on the IUCN's Red List. Due to their enormous size and conservation status, whale sharks are rarely housed in aquaria. Here we present a behavioral analysis culminating from a large effort by 89 observers from 2008-2012 to study four R. typus (ID codes: AL, TA, TR, YU) longitudinally in an aquarium setting. We found that relatively simple behavioral metrics such as swim speed, depth occupation, swimming direction, and lead-follow interactions demonstrated R. typus individual variation and responses to habitat changes. All sharks displayed increased swim speeds 30-minutes before regimented feed times, when there was scent of food being fed to other animals in the habitat. Consistently in the habitat, one male shark (YU) was recorded swimming more at depth, faster, almost exclusively clockwise, and engaged in fewer close proximity interactions with others than expected by chance. In contrast, a larger female shark (AL) was observed swimming the slowest, at the surface more than others, led other sharks more than she followed, and had strong lead-follow interactions with another shark of the opposite sex (TA). TA and TR did not differ from each other in depth profiles or speed, but did differ in their proclivity to lead or follow. Depth preferences and lead-follow interactions suggest some partitioning of the habitat and the possibility of social hierarchy in this species. These results represent the first longitudinal behavioral analysis of aquarium R. typus, offering meaningful similarities and contrasts to field observations. [ABSTRACT FROM AUTHOR]

In seasonally breeding animals, the costs and benefits of territorial aggression should vary over time; however, little work thus far has directly examined the scope and adaptive value of individual-level plasticity in aggression across breeding stages. We explore these issues using the tree swallow (Tachycineta bicolor), a single-brooded bird species in which females compete for limited nesting sites. We measured aggressiveness in nearly 100 females within 3 different stages: (1) shortly after territory-establishment, (2) during incubation, and (3) while caring for young chicks. Based on the timing, direction, and magnitude of behavioral changes between stages, we used k-means clustering to categorize each female's behavior into a "plasticity type." We then tested whether plasticity type and stage-specific aggression varied with key performance metrics. About 40% of females decreased aggressiveness across consecutive breeding stages to some degree, consistent with population-level patterns. 33% of females exhibited comparatively little plasticity, with moderate to low levels of aggression in all stages. Finally, 27% of females displayed steep decreases and then increases in aggression between stages; females exhibiting this pattern had significantly lower body mass while parenting, they tended to hatch fewer eggs, and they had the lowest observed overwinter survival rates. Other patterns of among-stage changes in aggressiveness were not associated with performance. These results reveal substantial among-individual variation in behavioral plasticity, which may reflect diverse solutions to trade-offs between current reproduction and future survival. [ABSTRACT FROM AUTHOR]

An understanding of individual variation in animal habitat selection is important for effective conservation and management as well as predicting species responses to a rapidly changing world. Functional responses to habitat availability can explain some of this variation, but not accounting for behavioral grouping may oversimplify inference and mask the diversity of habitat use strategies present in a population. We investigated within-home range habitat selection variation at the group level in a reintroduced population of elk (Cervus canadensis) in Kentucky, USA, during 2020–2022, analyzing satellite tracking data from 103 individuals to quantify variance in responses to seven landscape variables. We used group-level selection coefficients estimated with mixed-effects resource selection functions to model population-level functional responses and classify groups into within-season behavioral clusters. We then used cross validation to assess if these methods of generalizing group-level variation improved predictions of space use. We found that elk had highly variable responses to several covariates, and that some of this variation could be attributed to functional responses to either cover type availability or configuration. When we generalized behavioral tactics via clustering, we found significant increases in group-level predictive ability over the global model and, in some cases, the functional models. This suggests that clustered behaviors are also driving individual heterogeneity in this population. Our results highlight the importance of considering individual differences when studying wildlife-habitat relationships and underscore the need for a more complete understanding of the mechanisms behind this variation to inform habitat management and conservation efforts. [ABSTRACT FROM AUTHOR]

Knowledge of seabird distributions plays a key role in seabird conservation and sustainable marine management, underpinning efforts to designate protected areas or assess the impact of human developments. Technological advances in animal tracking devices increasingly allow researchers to acquire information on the movement of birds from specific colonies. Nevertheless, most seabird colonies have not been subject to such tracking and another means must be found to assess their likely foraging distribution. Consequently, foraging range data collated and summarized across other tracking studies has often been used to estimate species‐level foraging distances for use within applied settings. However, generic species‐specific foraging ranges must be used with caution because of the amount of variation in seabird foraging behaviour at both the individual and colony levels. Specifically, although current reviews of seabird foraging ranges provide summary estimates of maximum foraging range, they typically do not assess the extent of among‐colony or among‐individual variation around such estimates. To address this, we conducted a variance component analysis of the maximum distance reached from the breeding colony per foraging trip (foraging range) using multi‐colony tracking datasets to estimate the degree of between‐individual, between‐year and between‐colony variation in foraging range in four UK breeding seabirds (Black‐legged Kittiwake Rissa tridactyla, Common Guillemot Uria aalge, Razorbill Alca torda and European Shag Gulosus aristotelis). We also provide updated estimates of typical foraging ranges for each species and quantify the influence of breeding stage and colony size. Overall, between‐colony variation was typically the largest variance component, explaining 20–30% of the observed variation in foraging range across the four species. Individual‐level variation was also relatively large among Shag. In Kittiwake, Guillemot and Shag, but not Razorbill, average foraging ranges were positively associated with colony size. In addition, Kittiwake and Razorbill travelled further during incubation than during chick‐rearing. More generally, our estimates of mean foraging ranges for each species were subject to a high degree of uncertainty, which should be incorporated into impact assessments carried out using such data. [ABSTRACT FROM AUTHOR]

Understanding the evolution of traits subject to trade-offs is challenging because phenotypes can (co)vary at both the among- and within-individual levels. Among-individual covariation indicates consistent, possibly genetic, differences in how individuals resolve the trade-off, while within-individual covariation indicates trait plasticity. There is also the potential for consistent among-individual differences in behavioral plasticity, although this has rarely been investigated. We studied the sources of (co)variance in two characteristics of an acoustic advertisement signal that trade-off with one another and are under sexual selection in the gray treefrog, Hyla chrysoscelis : call duration and call rate. We recorded males on multiple nights calling spontaneously and in response to playbacks simulating different competition levels. Call duration, call rate, and their product, call effort, were all repeatable both within and across social contexts. Call duration and call rate covaried negatively, and the largest covariance was at the among-individual level. There was extensive plasticity in calling with changes in social competition, and we found some evidence for among-individual variance in call rate plasticity. The significant negative among-individual covariance in trait values is perpendicular to the primary direction of sexual selection in this species, indicating potential limits on the response to selection. [ABSTRACT FROM AUTHOR]

Intraspecific variation plays a pivotal role in shaping ecological dynamics. As the dispersal of seeds of most woody plants is mediated by animals, individual variation within the animal dispersers holds considerable implications for plant population and ecology.We explored how individual traits (such as sex, body mass and exploration levels) of yellow‐necked mice (Apodemus flavicollis) impact the dispersal of common oak (Quercus robur) acorns. Over 3 years, we collected data on seed fate and the specific mice responsible for their dispersal.The relationship between individual traits and seed dispersal was not static, but influenced by yearly environmental conditions. Heavier individuals tended to carry seeds farther, yet contrary to our expectations, sex had no effect on the distance of seed dispersal. Moreover, the exploration rate showed an inconsistent association with seed consumption and dispersal distance, while it positively impacted the distance of dispersal from the nearest tree.Synthesis. Our findings suggest a more nuanced role of individual traits in seed dispersal than often assumed, with noticeable annual variation significantly influencing these impacts. Consequently, it appears there is no single, universally beneficial individual type to ensure maximal benefits to plants. Rather, the traits conferring advantages in seed dispersal are dynamic, subject to change over time in response to environmental context. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Consistent individual differences in behavior ("animal personality") have consequences for individual fitness, evolutionary trajectories, and species' persistence. Such differences have been documented across a wide range of animals, though amphibians are generally underrepresented in this research area. The aim of our study was to examine consistent individual differences in Dyeing poison frogs, Dendrobates tinctorius. We evaluated repeatability in activity, exploration, and boldness to assess consistency of behaviors across different temporal, experimental, and environmental contexts. We found repeatability in activity and exploration across time and contexts. In contrast, we observed context-specific behavior for our metrics of boldness, with consistent individual differences only for some measures. Further, while activity and exploration displayed consistent correlations across contexts, relationships between activity and boldness were context dependent. Our findings document the presence of consistent individual differences in behavior in D. tinctorius poison frogs, and also reveal context-dependent behavioral differences, highlighting the complex relationship between consistent individual differences and context-specific responses in animal behavior. Significance statement: The concept of animal personality centers on the existence of consistent individual differences in behavior. However, behavioral responses can depend on context, and consistent individual differences in one context do not guarantee consistent differences in another. To address this question, we assessed activity, exploration, and boldness in captive-bred poison frogs (Dendrobates tinctorius) across time and environmental contexts. Our comprehensive approach revealed consistent individual differences in some behaviors and context-specificity in others. While activity and exploration were generally repeatable and correlated with one another, boldness was not. Especially in view of the emphasis on measures of boldness in the animal personality literature, our findings emphasize the importance of reiterative and holistic approaches in the study of animal behavior. [ABSTRACT FROM AUTHOR]

Migratory fish species have been particularly impacted by changes to the hydrologic and climatic cues to which migration and spawning behaviours have been adapted across generations. While conservation and recovery programs increasingly implement flow management actions to promote successful migration and spawning, uncertainty regarding how spawning migration phenology responds to changing environmental conditions can limit the ability to effectively target such recovery actions. Here, we use a Bayesian hierarchical modelling framework to analyse spawning migration phenology of individually tagged June suckers (Chasmistes liorus) – a federally threatened, long‐lived, iteroparous, adfluvial species endemic to Utah Lake (Utah, USA) and its tributaries. We then examine how annual hydrologic and thermal conditions relate to different components of annual migration phenology, including peak migration date, in‐stream residence time, and among‐individual variation in migration timing. Peak migration date occurred earlier in years with warmer spring air temperatures (a proxy for water temperatures), though this effect interacted with peak runoff timing. Both residence time and among‐individual variation in migration timing were greater in years with larger spring discharge and later peak flows. Residence time was also longer in warmer years. These results highlight how natural and anthropogenic changes to river flow and thermal regimes are likely to impact June sucker migration timing and duration, and our approach can be applied to other migratory species to identify the external drivers of the different components of migration phenology. [ABSTRACT FROM AUTHOR]

The maximum rate at which fish can take up oxygen from their environment to fuel aerobic metabolism is an important feature of their physiology and ecology. Methods to quantify maximum oxygen uptake rate (ṀO2), therefore, should reliably and reproducibly estimate the highest possible ṀO2 by an individual or species under a given set of conditions (peak ṀO2). This study determined peak ṀO2 and its repeatability in Gulf killifish, Fundulus grandis, subjected to three methods to elevate metabolism: swimming at increasing water speeds, during recovery after an exhaustive chase, and after ingestion of a large meal. Estimates of peak ṀO2 during swimming and after an exhaustive chase were repeatable across two trials, whereas peak ṀO2 after feeding was not. Peak ṀO2 determined by the three methods was significantly different from one another, being highest during swimming, lowest after an exhaustive chase, and intermediate after feeding. In addition, peak ṀO2 during recovery from an exhaustive chase depended on the length of time of recovery: in nearly 60% of the trials, values within the first hour of the chase were lower than those measured later. A novel and important finding was that an individual's peak ṀO2 was not repeatable when compared across methods. Therefore, the peak ṀO2 estimated for a group of fish, as well as the ranking of individual ṀO2 within that group, depends on the method used to elevate aerobic metabolism. [ABSTRACT FROM AUTHOR]

Stomach morphology can provide insights into an organism's diet. Gut size or length is typically inversely related to diet quality in most taxa, and has been used to assess diet quality in a variety of systems. However, it requires animal sacrifice and time‐consuming dissections. Measures of external morphology associated with diet may be a simpler, more cost‐effective solution. At the species level, external measures of the progastric region of the carapace in brachyuran crabs can predict stomach size and diet quality, with some suggestion that this approach may also work to examine individual diet preferences and specialization at the individual level; if so, the size of the progastric region could be used to predict trends in diet quality and consumption for individuals, which would streamline diet studies in crabs. Here, we tested whether external progastric region size predicts internal stomach size across latitude and time of year for individuals of the invasive Asian shore crab Hemigrapsus sanguineus. We found that the width of the progastric region increased at a faster rate with body size than stomach width. In addition, the width of the progastric region followed different trends across sites and over time compared to stomach width. Our results therefore suggest that the progastric region may not be used as a proxy for stomach size variation across individuals. [ABSTRACT FROM AUTHOR]

Abstract Wildlife depends on specific landscape features to persist. Thus, characterizing the vegetation available in an area can be essential for management. The ocelot (Leopardus pardalis) is a federally endangered, medium‐sized felid adapted to woody vegetation. Quantifying the characteristics of vegetation most suitable for ocelots is essential for their conservation. Furthermore, understanding differences in the selection of sympatric bobcats (Lynx rufus) and coyotes (Canis latrans) can provide insight into the mechanisms of coexistence between species. Because of differences in hunting strategy (cursorial vs. ambush) and differences in use of land cover types between species, these three carnivores may be partitioning their landscape as a function of vegetation structure. Light detection and ranging (LiDAR) is a remote sensing platform capable of quantifying the sub‐canopy structure of vegetation. Using LiDAR data, we quantified the horizontal and vertical structure of vegetation cover to assess habitat selection by ocelots, bobcats, and coyotes. We captured and collared 8 ocelots, 13 bobcats, and 5 coyotes in southern Texas from 2017 to 2021. We used step selection functions to determine the selection of vegetation cover at the population and individual level for each species. Ocelots selected for vertical canopy cover and dense vegetation 0–2 m in height. Bobcats selected cover to a lesser extent and had a broader selection, while coyotes avoided under‐story vegetation and selected areas with dense high canopies and relatively open understories. We observed a high degree of variation among individuals that may aid in facilitating intraspecific and interspecific coexistence. Management for ocelots should prioritize vegetation below 2 m and vertical canopy cover. We provide evidence that fine‐scale habitat partitioning may facilitate coexistence between sympatric carnivores. Differences among individuals may enhance coexistence among species, as increased behavioral plasticity of individuals can reduce competition for resources. By combining accurate, fine‐scale measurements derived from LiDAR data with high‐frequency global positioning system locations, we provide a more thorough understanding of the habitat use of ocelots and two sympatric carnivores.

With its estrogenic activity, (S)-equol plays an important role in maintaining host health and preventing estrogen-related diseases. Exclusive production occurs through the transformation of soy isoflavones by intestinal bacteria, but the reasons for variations in (S)-equol production among different individuals and species remain unclear. Here, fecal samples from humans, pigs, chickens, mice, and rats were used as research objects. The concentrations of (S)-equol, along with the genetic homology and evolutionary relationships of (S)-equol production-related genes [daidzein reductase (DZNR), daidzein racemase (DDRC), dihydrodaidzein reductase (DHDR), tetrahydrodaidzein reductase (THDR)], were analyzed. Additionally, in vitro functional verification of the newly identified DDRC gene was conducted. It was found that approximately 40% of human samples contained (S)-equol, whereas 100% of samples from other species contained (S)-equol. However, there were significant variations in (S)-equol content among the different species: rats > pigs > chickens > mice > humans. The distributions of the four genes displayed species-specific patterns. High detection rates across various species were exhibited by DHDR, THDR, and DDRC. In contrast, substantial variations in detection rates among different species and individuals were observed with respect to DZNR. It appears that various types of DZNR may be associated with different concentrations of (S)-equol, which potentially correspond to the regulatory role during (S)-equol synthesis. This enhances our understanding of individual variations in (S)-equol production and their connection with functional genes in vitro. Moreover, the newly identified DDRC exhibits higher potential for (S)-equol synthesis compared to the known DDRC, providing valuable resources for advancing in vitro (S)-equol production. IMPORTANCE (S)-equol ((S)-EQ) plays a crucial role in maintaining human health, along with its known capacity to prevent and treat various diseases, including cardiovascular diseases, metabolic syndromes, osteoporosis, diabetes, brain-related diseases, high blood pressure, hyperlipidemia, obesity, and inflammation. However, factors affect ing individual variations in (S)-EQ production and the underlying regulatory mechanisms remain elusive. This study examines the association between functional genes and (S)-EQ production, highlighting a potential correlation between the DZNR gene and (S)-EQ content. Various types of DZNR may be linked to the regulation of (S)-EQ synthesis. Furthermore, the identification of a new DDRC gene offers promising prospects for enhancing in vitro (S)-EQ production. [ABSTRACT FROM AUTHOR]

Wildlife depends on specific landscape features to persist. Thus, characterizing the vegetation available in an area can be essential for management. The ocelot (Leopardus pardalis) is a federally endangered, medium‐sized felid adapted to woody vegetation. Quantifying the characteristics of vegetation most suitable for ocelots is essential for their conservation. Furthermore, understanding differences in the selection of sympatric bobcats (Lynx rufus) and coyotes (Canis latrans) can provide insight into the mechanisms of coexistence between species. Because of differences in hunting strategy (cursorial vs. ambush) and differences in use of land cover types between species, these three carnivores may be partitioning their landscape as a function of vegetation structure. Light detection and ranging (LiDAR) is a remote sensing platform capable of quantifying the sub‐canopy structure of vegetation. Using LiDAR data, we quantified the horizontal and vertical structure of vegetation cover to assess habitat selection by ocelots, bobcats, and coyotes. We captured and collared 8 ocelots, 13 bobcats, and 5 coyotes in southern Texas from 2017 to 2021. We used step selection functions to determine the selection of vegetation cover at the population and individual level for each species. Ocelots selected for vertical canopy cover and dense vegetation 0–2 m in height. Bobcats selected cover to a lesser extent and had a broader selection, while coyotes avoided under‐story vegetation and selected areas with dense high canopies and relatively open understories. We observed a high degree of variation among individuals that may aid in facilitating intraspecific and interspecific coexistence. Management for ocelots should prioritize vegetation below 2 m and vertical canopy cover. We provide evidence that fine‐scale habitat partitioning may facilitate coexistence between sympatric carnivores. Differences among individuals may enhance coexistence among species, as increased behavioral plasticity of individuals can reduce competition for resources. By combining accurate, fine‐scale measurements derived from LiDAR data with high‐frequency global positioning system locations, we provide a more thorough understanding of the habitat use of ocelots and two sympatric carnivores. [ABSTRACT FROM AUTHOR]

Mathematical models are increasingly adopted for setting disease prevention and control targets. As model-informed policies are implemented, however, the inaccuracies of some forecasts become apparent, for example overprediction of infection burdens and intervention impacts. Here, we attribute these discrepancies to methodological limitations in capturing the heterogeneities of real-world systems. The mechanisms underpinning risk factors of infection and their interactions determine individual propensities to acquire disease. These factors are potentially so numerous and complex that to attain a full mechanistic description is likely unfeasible. To contribute constructively to the development of health policies, model developers either leave factors out (reductionism) or adopt a broader but coarse description (holism). In our view, predictive capacity requires holistic descriptions of heterogeneity which are currently underutilised in infectious disease epidemiology, in comparison to other population disciplines, such as non-communicable disease epidemiology, demography, ecology and evolution. [ABSTRACT FROM AUTHOR]

Repeated use of a winning foraging strategy can be profitable when individuals use memory to return to successful food patches. However, in environments where patches are unpredictable, variable foraging behaviour may be more profitable. To test this idea, we explored how individual variation in foraging trip characteristics impacts breeding success in black-legged kittiwakes, Rissa tridactyla , on Middleton Island, Alaska, U.S.A., during a period of highly variable environmental conditions, the largest recorded marine heatwave. As anticipated, foraging trip characteristics were highly variable, within and between years and individuals. While characteristics of foraging trips alone did not influence annual breeding success, both age and variance in those trip characteristics explained variation in breeding success. Specifically, individuals with smaller variance in foraging trip characteristics among trips were more likely to fledge a chick. There was a maximum distance threshold in foraging implying that individuals searched within a restricted area, increasing foraging time rather than distance when searching was not profitable, and providing additional support for the idea that kittiwakes are most successful when foraging in known areas rather than exploring new areas. The Pacific Decadal Oscillation, which is associated with large scale shifts between cold and warm ocean climate and ecosystem regimes in the region, impacted breeding success but did not change foraging behaviour. However, mean breeding success decreased as mean time spent resting and in area-restricted search (intensive search) on foraging trips during incubation increased. Based on nearly a decade of data, we conclude that smaller variability in behaviour, even during challenging foraging conditions, enhances breeding success. As climate change and marine heatwaves continue to increase in intensity, individuals more variable in foraging behaviour may be unable to compensate. • Individuals with less variation in foraging behaviour were more likely to fledge a chick. • There was evidence of a maximum distance threshold in foraging. • Pacific Decadal Oscillation impacted breeding success but not foraging behaviour. [ABSTRACT FROM AUTHOR]

Rhincodon typus, or the whale shark, is the largest extant fish in the world and is classified as endangered on the IUCN’s Red List. Due to their enormous size and conservation status, whale sharks are rarely housed in aquaria. Here we present a behavioral analysis culminating from a large effort by 89 observers from 2008–2012 to study four R. typus (ID codes: AL, TA, TR, YU) longitudinally in an aquarium setting. We found that relatively simple behavioral metrics such as swim speed, depth occupation, swimming direction, and lead-follow interactions demonstrated R. typus individual variation and responses to habitat changes. All sharks displayed increased swim speeds 30-minutes before regimented feed times, when there was scent of food being fed to other animals in the habitat. Consistently in the habitat, one male shark (YU) was recorded swimming more at depth, faster, almost exclusively clockwise, and engaged in fewer close proximity interactions with others than expected by chance. In contrast, a larger female shark (AL) was observed swimming the slowest, at the surface more than others, led other sharks more than she followed, and had strong lead-follow interactions with another shark of the opposite sex (TA). TA and TR did not differ from each other in depth profiles or speed, but did differ in their proclivity to lead or follow. Depth preferences and lead-follow interactions suggest some partitioning of the habitat and the possibility of social hierarchy in this species. These results represent the first longitudinal behavioral analysis of aquarium R. typus, offering meaningful similarities and contrasts to field observations.

The topological organization of the macroscopic cortical networks important for the development of complex brain functions. However, how the cortical morphometric organization develops during the third trimester and whether it demonstrates sexual and individual differences at this particular stage remain unclear. Here, we constructed the morphometric similarity network (MSN) based on morphological and microstructural features derived from multimodal MRI of two independent cohorts (cross-sectional and longitudinal) scanned at 30–44 postmenstrual weeks (PMW). Sex difference and inter-individual variations of the MSN were also examined on these cohorts. The cross-sectional analysis revealed that both network integration and segregation changed in a nonlinear biphasic trajectory, which was supported by the results obtained from longitudinal analysis. The community structure showed remarkable consistency between bilateral hemispheres and maintained stability across PMWs. Connectivity within the primary cortex strengthened faster than that within high-order communities. Compared to females, male neonates showed a significant reduction in the participation coefficient within prefrontal and parietal cortices, while their overall network organization and community architecture remained comparable. Furthermore, by using the morphometric similarity as features, we achieved over 65 % accuracy in identifying an individual at term-equivalent age from images acquired after birth, and vice versa. These findings provide comprehensive insights into the development of morphometric similarity throughout the perinatal cortex, enhancing our understanding of the establishment of neuroanatomical organization during early life.

Abstract Stomach morphology can provide insights into an organism's diet. Gut size or length is typically inversely related to diet quality in most taxa, and has been used to assess diet quality in a variety of systems. However, it requires animal sacrifice and time‐consuming dissections. Measures of external morphology associated with diet may be a simpler, more cost‐effective solution. At the species level, external measures of the progastric region of the carapace in brachyuran crabs can predict stomach size and diet quality, with some suggestion that this approach may also work to examine individual diet preferences and specialization at the individual level; if so, the size of the progastric region could be used to predict trends in diet quality and consumption for individuals, which would streamline diet studies in crabs. Here, we tested whether external progastric region size predicts internal stomach size across latitude and time of year for individuals of the invasive Asian shore crab Hemigrapsus sanguineus. We found that the width of the progastric region increased at a faster rate with body size than stomach width. In addition, the width of the progastric region followed different trends across sites and over time compared to stomach width. Our results therefore suggest that the progastric region may not be used as a proxy for stomach size variation across individuals.

Habitat selection analyses conducted at an individual level may reveal patterns in selection not apparent when individuals are pooled in population‐level approaches. Using GPS transmitters that gather high‐resolution location data, we explored fine‐scale habitat selection and space use within home ranges of female greater sage‐grouse Centrocercus urophasianus that raised young (brood‐rearing sage‐grouse) in an oil and gas development area. To evaluate fine‐scale habitat selection of brood‐rearing sage‐grouse we used a two‐stage approach. First, we developed models for each individual (i.e. individual‐level modeling) and evaluated individual‐level responses to modified habitats and infrastructure. Second, we averaged individual‐level estimates using a bootstrap approach to make population‐level inference. The average home range size during brood‐rearing in our study, from nest hatch to six weeks, was 0.85 ± 0.21 km2. Individual and population‐level results indicated that brood‐rearing females consistently selected for natural vegetation and avoided disturbed surfaces at a fine spatial scale. Our study area included substantial areas of recent (≤ 10 years) habitat reclamation which females also avoided. Visible power lines consistently led to avoidance behavior. In addition to consistent patterns of habitat selection, our individual models demonstrated variability and contrasting behaviors in how brood‐rearing females responded to specific infrastructure features and anthropogenic water bodies. At the population‐level anthropogenic water bodies were avoided but at the individual‐level the intensity of avoidance was variable among individuals. Individual variability was often explained by the age of the brood‐rearing female (first year or adult). First year females were more likely than adults to use habitats close to infrastructure and consistently established home ranges in areas with more surface disturbance and infrastructure when compared to adults. Our results provide new insights into fine‐scale habitat‐selection strategies used by female sage‐grouse with broods in an area where oil and gas infrastructure is widespread and cannot be avoided. [ABSTRACT FROM AUTHOR]

Individual laying hens within the same group show variation in their temperament traits and cognitive learning abilities, which can be affected by both their early rearing experiences and housing environments. Hens also have distinct individual patterns of movement within housing systems that may correlate with temperament and cognition. Individual behavioral tests can measure treatment impacts, but social dynamics may impact on an individual's behavior. The aims of this perspective piece are to provide further evidence of pen-level variation using original data on social ranging patterns and fear assessment of free-range hens exposed to different, enriched rearing environments; and to encourage more studies to consider pen replicate variation as a means to better understand causes and mechanisms. A literature review showed that, while most published studies over the past decade assessing individual laying hen behavior included group-level replication (i.e., 83% of 54 articles reviewed), almost none considered interpen variation. The original data analysis of individual hens' range use recordings showed significant treatment pen replicate variation in pop-hole following movements and hen-pair associations in the time spent together inside or outside. Significant inter-pen variation was also seen in tonic immobility tests on a subset of hens from the same study. Pen-level replication is important for scientific validity and for improving our understanding of why commercial flocks in the same environment can be so variable in their behavior to inform management practices. Further research could help to understand the mechanisms behind why groups of hens reared and housed in the same environments will show significant inter-group variation. [ABSTRACT FROM AUTHOR]

Anthropogenic noise is a pollutant of growing concern, with wide‐ranging effects on taxa across ecosystems. Until recently, studies investigating the effects of anthropogenic noise on animals focused primarily on population‐level consequences, rather than individual‐level impacts. Individual variation in response to anthropogenic noise may result from extrinsic or intrinsic factors. One such intrinsic factor, cognitive performance, varies between individuals and is hypothesised to aid behavioural response to novel stressors. Here, we combine cognitive testing, behavioural focals and playback experiments to investigate how anthropogenic noise affects the behaviour and anti‐predator response of Western Australian magpies (Gymnorhina tibicen dorsalis), and to determine whether this response is linked to cognitive performance. We found a significant population‐level effect of anthropogenic noise on the foraging effort, foraging efficiency, vigilance, vocalisation rate and anti‐predator response of magpies, with birds decreasing their foraging, vocalisation behaviours and anti‐predator response, and increasing vigilance when loud anthropogenic noise was present. We also found that individuals varied in their response to playbacks depending on their cognitive performance, with individuals that performed better in an associative learning task maintaining their anti‐predator response when an alarm call was played in anthropogenic noise. Our results add to the growing body of literature documenting the adverse effects of anthropogenic noise on wildlife and provide the first evidence for an association between individual cognitive performance and behavioural responses to anthropogenic noise. [ABSTRACT FROM AUTHOR]

This paper explores the different ways in which speakers of Limburgian think and feel about sociopragmatic pronouns in their dialect, in which women can traditionally be referred to with both ziej 'she' and het 'she' (lit. 'it'). Previous research revealed variation between speakers regarding the use of het, which appears to be associated with differences in interpretation and evaluation. This study investigates this further by analyzing how individual speakers evaluate non-feminine pronouns for women. Our data show that many speakers have a relatively high level of awareness, discussing four key themes: (i) how female reference in Limburgian differs from that of Dutch; (ii) the appropriateness of using the pronouns for certain referents and/or in certain social situations; (iii) the various connotations the pronouns may have; and (iv) how they navigate between-speaker differences regarding pronoun evaluation in daily life. Importantly, this high level of awareness is not present in all speakers. These results indicate that the use or non-use of the pronoun het for female referents may be conditioned by cognitive automaticity for some speakers, and by a conscious, emotionally charged consideration about its desirability for others. Our findings, therefore, suggest the importance of integrating cognition and sociality in linguistic theorizing. [ABSTRACT FROM AUTHOR]

This paper defines functional cold exposure zones that illustrate whether a person is at risk of developing physical performance loss or cold weather injuries. Individual variation in body characteristics, activity level, clothing and protective equipment all contribute to variation in the effective exposure. Nevertheless, with the right education, training, and cold-adapted behaviours the exposure differences might not necessarily lead to increased risk for cold injury. To support the preparation process for cold weather operations, this paper presents a biophysical analysis explaining how much cold exposure risk can vary between individuals in the same environment. The results suggest that smaller persons are prone to be underdressed for moderate activity levels and larger persons are prone to be overdressed. The consequences of these discrepancies place people at different risks for performance loss or cold weather injuries. Nonetheless, even if all are well-dressed at the whole-body level, variation in hand morphology is also expected to influence hand skin temperatures that can be maintained; with smaller hands being more prone to reach skin temperatures associated with dexterity loss or cold weather injuries. In conclusion, this work focusses on bringing cold science to the Arctic warrior, establishing that combating cold stress is not a one size fits all approach. [ABSTRACT FROM AUTHOR]

We lack synthesis of the study of local mechanisms that contribute to the persistence of populations (i.e., buffer mechanisms). Local buffer mechanisms can be integrated into a framework consisting of the two basic classes of repelling and damping mechanisms. The framework promotes a more coherent picture of buffer mechanisms and facilitates a better integration of multiple buffer mechanisms in studies of population persistence. Individual-based studies are essential to improve our understanding of the role of local buffer mechanisms in shaping population dynamics and their capacities and interactions. Assessing and predicting the persistence of populations is essential for the conservation and control of species. Here, we argue that local mechanisms require a better conceptual synthesis to facilitate a more holistic consideration along with regional mechanisms known from metapopulation theory. We summarise the evidence for local buffer mechanisms along with their capacities and emphasise the need to include multiple buffer mechanisms in studies of population persistence. We propose an accessible framework for local buffer mechanisms that distinguishes between damping (reducing fluctuations in population size) and repelling (reducing population declines) mechanisms. We highlight opportunities for empirical and modelling studies to investigate the interactions and capacities of buffer mechanisms to facilitate better ecological understanding in times of ecological upheaval. [ABSTRACT FROM AUTHOR]

Speakers adjust their pronunciation to come to sound more similar to recently heard speech in a phenomenon called phonetic imitation. The extent to which speakers imitate is commonly measured using the AXB perception task, which relies on the judgements of listeners. Despite its popularity, very few studies using the AXB assessment have considered variation or reliability in the listeners’ performance. The current study applies a test-retest methodology focusing on the performance of listeners in the AXB assessment of imitation, which has not been considered explicitly before. Forty listeners completed the same AXB experiment twice, two to three weeks apart. The findings showed that both sessions reach the same overall conclusion: the listeners perceived the same overall amount of imitation in both sessions, which is taken to mean that the shadowers did imitate and that the AXB task is reliable at the group level. Furthermore, the findings show that listeners vary substantially in their performance in the AXB assessment of imitation, but that they are relatively consistent in this performance across sessions. This suggests that differences in AXB performance at least partly reflect differences in ability to perceive imitation, rather than simply random variation.

Individual laying hens within the same group show variation in their temperament traits and cognitive learning abilities, which can be affected by both their early rearing experiences and housing environments. Hens also have distinct individual patterns of movement within housing systems that may correlate with temperament and cognition. Individual behavioral tests can measure treatment impacts, but social dynamics may impact on an individual’s behavior. The aims of this perspective piece are to provide further evidence of pen-level variation using original data on social ranging patterns and fear assessment of free-range hens exposed to different, enriched rearing environments; and to encourage more studies to consider pen replicate variation as a means to better understand causes and mechanisms. A literature review showed that, while most published studies over the past decade assessing individual laying hen behavior included group-level replication (i.e., 83% of 54 articles reviewed), almost none considered inter-pen variation. The original data analysis of individual hens’ range use recordings showed significant treatment pen replicate variation in pop-hole following movements and hen–pair associations in the time spent together inside or outside. Significant inter-pen variation was also seen in tonic immobility tests on a subset of hens from the same study. Pen-level replication is important for scientific validity and for improving our understanding of why commercial flocks in the same environment can be so variable in their behavior to inform management practices. Further research could help to understand the mechanisms behind why groups of hens reared and housed in the same environments will show significant inter-group variation.

ABSTRACTThis paper defines functional cold exposure zones that illustrate whether a person is at risk of developing physical performance loss or cold weather injuries. Individual variation in body characteristics, activity level, clothing and protective equipment all contribute to variation in the effective exposure. Nevertheless, with the right education, training, and cold-adapted behaviours the exposure differences might not necessarily lead to increased risk for cold injury. To support the preparation process for cold weather operations, this paper presents a biophysical analysis explaining how much cold exposure risk can vary between individuals in the same environment. The results suggest that smaller persons are prone to be underdressed for moderate activity levels and larger persons are prone to be overdressed. The consequences of these discrepancies place people at different risks for performance loss or cold weather injuries. Nonetheless, even if all are well-dressed at the whole-body level, variation in hand morphology is also expected to influence hand skin temperatures that can be maintained; with smaller hands being more prone to reach skin temperatures associated with dexterity loss or cold weather injuries. In conclusion, this work focusses on bringing cold science to the Arctic warrior, establishing that combating cold stress is not a one size fits all approach.

IntroductionThere is evidence of close links between the allocation of attention and the production of language. For instance, while speakers commonly produce active sentences when they describe an event with an agent acting on a patient, this preference can shift once the patient is in the spotlight of attention (e.g., by means of a brief attentional cue preceding the patient). In this case, speakers are more prone to produce non-canonical sentences such as passives. Critically, however, whereas attentional cueing is particularly effective for speakers of English, it has proven less effective for speakers of languages like German that differ from English in terms of case-marking and word order flexibility. This observation begs the question of how German speakers respond to alternative cue types that differ in the conceptual and lexical information they provide. In the current study, we address this question by directly comparing the effect of different cue types on sentence production.MethodsGerman-speaking participants were asked to describe transitive event scenes while their eye gaze was monitored via eye tracking. Prior to scene onset, participants saw one of three different cue types: a short attentional cue preceding the patient character, a long attentional cue, or a centrally presented pre-view of the patient (referential cue).Results and discussionOur results demonstrate that different cue types led to differences in speakers' propensity to produce passives. Critically, referential cueing was more effective than attentional cueing in increasing German speakers' rate of passive production, contra to what has previously been reported for English speakers. At the same time, the cues resulted in different viewing behavior, demonstrating that an increase in visual attention does not necessarily go hand in hand with an increase in passivization. Consequently, our findings show that a direct link between the allocation of attention and speakers' structural choices may not always be licensed.

Observational fear-learning studies in genetically modified animals enable the investigation of the mechanisms underlying the social transmission of fear-related information. Here, we used a three-day protocol to examine fear conditioning by proxy (FCbP) in wild-type mice (C57BL/6J) and mice lacking the β2-subunit of the nicotinic acetylcholine receptor (nAChR). Male animals of both genotypes were exposed to a previously fear-conditioned (FC) cage mate during the presentation of the conditioned stimulus (CS, tone). On the following day, observer (FCbP) mice were tested for fear reactions to the tone: none of the β2-KO mice froze to the stimulus, while 30% of the wild-type mice expressed significant freezing. An investigation of the possible factors that predicted the fear response revealed that only wild-type mice that exhibited enhanced and more flexible social interaction with the FC cage mate during tone presentations (Day 2) expressed fear toward the CS (Day-3). Our results indicate that (i) FCbP is possible in mice; (ii) the social transmission of fear depends on the interaction pattern between animals during the FCbP session and (iii) β2-KO mice display a more rigid interaction pattern compared to wild-type mice and are unable to acquire such information. These data suggest that β2-nAChRs influence observational fear learning indirectly through their effect on social behaviour. [ABSTRACT FROM AUTHOR]

Social behaviours can allow individuals to flexibly respond to environmental change, potentially buffering adverse effects. However, individuals may respond differently to the same environmental stimulus, complicating predictions for population-level response to environmental change. Here, we show that bottlenose dolphins (Tursiops truncatus) alter their social behaviour at yearly and monthly scales in response to a proxy for food availability (salmon abundance) but do not respond to variation in a proxy for climate (the North Atlantic Oscillation index). There was also individual variation in plasticity for gregariousness and connectedness to distant parts of the social network, although these traits showed limited repeatability. By contrast, individuals showed consistent differences in clustering with their immediate social environment at the yearly scale but no individual variation in plasticity for this trait at either timescale. These results indicate that social behaviour in free-ranging cetaceans can be highly resource dependent with individuals increasing their connectedness over short timescales but possibly reducing their wider range of connection at longer timescales. Some social traits showed more individual variation in plasticity or mean behaviour than others, highlighting how predictions for the responses of populations to environmental variation must consider the type of individual variation present in the population. [ABSTRACT FROM AUTHOR]

Individuals generally differ in their ability to perform challenging behaviours, but the causes of such variability remain incompletely understood. Because animals can usually use different behavioural tactics to achieve their goals, we might expect individual differences in skill to be maintained when the available tactics require different abilities to perform well. To explore this idea, I used the producer‐scrounger (PS) paradigm, which considers interactions between foragers that may either invest effort in searching for resources (i.e. produce) or exploit others' discoveries (i.e. scrounge). Specifically, I tested whether individual differences in cognitive traits (i.e. the ability to find food) might result from a trade‐off with competitiveness (i.e. the ability to steal food) that would exert disruptive selection pressure and, as such, might explain the coexistence of condition‐dependent foraging tactics. If individuals differ in their competitiveness, with strong contestants being better able to monopolize food resources (and hence to scrounge), the model predicts that strong and weak competitors should rely more on scrounging and producing, respectively, especially when the finder's advantage is low. These findings indicate that the existence of individual differences in competitive abilities may be sufficient to explain short‐term individual foraging tactic specialization. Yet, the degree of behavioural specialization is expected to depend on both the social and ecological context. Furthermore, persistent phenotypic differences, that are necessary for stable individual specialization, require the existence of a trade‐off between competitive abilities that enable greater success as scroungers and cognitive abilities that are associated with better efficiency to detect and/or capture prey and, as such, enable greater success as producers. Therefore, this study further highlights the importance of considering the existence of alternative tactics to measure and predict the evolution of traits, including cognitive traits, within populations. [ABSTRACT FROM AUTHOR]

In granivorous songbirds, feeding is a complex process as seeds need to be dehusked before they can be consumed, making the feeding act a biomechanically challenging endeavour. However, most previous research has focused on how beak morphology affects feeding performance, while the influences of beak kinematics remain largely unknown.In this study, we hence investigated at the individual level how feeding performance (i.e. seed processing time and success rate) relates to both beak kinematics (i.e. beak tip speed, acceleration, frequency) and skill (i.e. seed handling tactics and cracking techniques) in the Canary Serinus canaria. To do so, high‐speed videos during feeding were recorded and subjected to automated tracking of beak tip movements.Better skills, that is accurate positioning of the seed for being split in half, reduced total seed handling time compared to more random positioning and crushing the husk into multiple, scattering fragments. Surprisingly, individual variation in beak speed, acceleration or frequency generally did not relate to differences in performance.Thus, our data suggest that seed positioning precision, and hence the control of coordinated beak and tongue movement, is critical to minimize feeding durations in songbirds. Further studies are needed to explore whether this develops via a positive feedback between behaviour, learning and increased efficiency or if it relates to intrinsic differences. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

This study investigates sources of phonological cross-linguistic influence (CLI) at the initial stages of third language (L3) acquisition in light of the predictions of the second language (L2) Status Factor Model, the Typological Primacy Model, the Cumulative Enhancement Model, the Linguistic Proximity Model and the Scalpel Model. The productions of L3 rhotic sounds, /w/ and final obstruent devoicing, elicited in a delayed repetition task, were analysed auditorily in two groups of adolescent instructed learners with L1-German–L2-English–L3-Polish and L1-Polish–L2-English–L3-German language backgrounds. The results showed that dominant articulatory routines from the L1 play an important role in determining the source(s) of phonological CLI in the initial stages of L3 acquisition, at least in a learning constellation when L2 articulations have not been mastered yet in a consistently target-like manner. Based on loglinear and multiple correspondence analyses, the sources of phonological CLI were found in this study to vary feature-by-feature, thus giving some support to the Linguistic Proximity Model and the Scalpel Model. However, the high inter- and intra-individual variation that was found is so far not accounted for by any of the existing models. [ABSTRACT FROM AUTHOR]

There have been some suggestions in linguistics and cognitive science that humans process continuous speech by routinely chunking it up into smaller units. The nature of the process is open to debate, which is complicated by the apparent existence of two entirely different chunking processes, both of which seem to be warranted by the limitations of working memory. To overcome them, humans seem to both combine items into larger units for future retrieval (usage-based chunking), and partition incoming streams into temporal groups (perceptual chunking). To determine linguistic properties and cognitive constraints of perceptual chunking, most previous research has employed short-constructed stimuli modeled on written language. In contrast, we presented linguistically naïve listeners with excerpts of natural speech from corpora and collected their intuitive perceptions of chunk boundaries. We then used mixed-effects logistic regression models to find out to what extent pauses, prosody, syntax, chunk duration, and surprisal predict chunk boundary perception. The results showed that all cues were important, suggesting cue degeneracy, but with substantial variation across listeners and speech excerpts. Chunk duration had a strong effect, supporting the cognitive constraint hypothesis. The direction of the surprisal effect supported the distinction between perceptual and usage-based chunking. [ABSTRACT FROM AUTHOR]

Abstract Individuals generally differ in their ability to perform challenging behaviours, but the causes of such variability remain incompletely understood. Because animals can usually use different behavioural tactics to achieve their goals, we might expect individual differences in skill to be maintained when the available tactics require different abilities to perform well. To explore this idea, I used the producer‐scrounger (PS) paradigm, which considers interactions between foragers that may either invest effort in searching for resources (i.e. produce) or exploit others' discoveries (i.e. scrounge). Specifically, I tested whether individual differences in cognitive traits (i.e. the ability to find food) might result from a trade‐off with competitiveness (i.e. the ability to steal food) that would exert disruptive selection pressure and, as such, might explain the coexistence of condition‐dependent foraging tactics. If individuals differ in their competitiveness, with strong contestants being better able to monopolize food resources (and hence to scrounge), the model predicts that strong and weak competitors should rely more on scrounging and producing, respectively, especially when the finder's advantage is low. These findings indicate that the existence of individual differences in competitive abilities may be sufficient to explain short‐term individual foraging tactic specialization. Yet, the degree of behavioural specialization is expected to depend on both the social and ecological context. Furthermore, persistent phenotypic differences, that are necessary for stable individual specialization, require the existence of a trade‐off between competitive abilities that enable greater success as scroungers and cognitive abilities that are associated with better efficiency to detect and/or capture prey and, as such, enable greater success as producers. Therefore, this study further highlights the importance of considering the existence of alternative tactics to measure and predict the evolution of traits, including cognitive traits, within populations.

Craving reflects the subjective urge to use drugs and can be triggered by both positive and negative emotional states. No studies have systematically investigated the relative roles of these mechanisms in the pathophysiology of substance misuse. Here, we performed meta-analyses of drug cue-elicited reactivity and win and loss processing in the monetary incentive delay task to identify distinct neural correlates of appetitive and aversive responses to drug cues. We then characterized the appetitive and aversive cue responses in seventy-six alcohol drinkers performing a cue craving task during fMRI. Imaging data were processed according to published routines. The appetitive circuit involved medial cortical regions and the ventral striatum, and the aversive circuit involved the insula, caudate and mid-cingulate cortex. We observed a significant correlation of cue-elicited activity (β estimates) of the appetitive and aversive circuit. However, individuals varied in appetitive and aversive cue responses. From the regression of appetitive (y) vs. aversive (x) β, we identified participants in the top 1/3 each of those with positive and negative residuals as “approach” (n = 15) and “avoidance” (n = 11) and the others as the “mixed” (n = 50) subtype. In clinical characteristics, the avoidance subtype showed higher sensitivity to punishment and, in contrast, the approach subtype showed higher levels of sensation seeking and alcohol expectancy for social and physical pressure. The findings highlighted distinct neural underpinnings of appetitive and aversive components of cue-elicited reactivity and provided evidence for potential subtypes of alcohol drinkers.

Many genes are co‐expressed and form genomic domains of coordinated gene activity. However, the regulatory determinants of domain co‐activity remain unclear. Here, we leverage human individual variation in gene expression to characterize the co‐regulatory processes underlying domain co‐activity and systematically quantify their effect sizes. We employ transcriptional decomposition to extract from RNA expression data an expression component related to co‐activity revealed by genomic positioning. This strategy reveals close to 1,500 co‐activity domains, covering most expressed genes, of which the large majority are invariable across individuals. Focusing specifically on domains with high variability in co‐activity reveals that contained genes have a higher sharing of eQTLs, a higher variability in enhancer interactions, and an enrichment of binding by variably expressed transcription factors, compared to genes within non‐variable domains. Through careful quantification of the relative contributions of regulatory processes underlying co‐activity, we find transcription factor expression levels to be the main determinant of gene co‐activity. Our results indicate that distal trans effects contribute more than local genetic variation to individual variation in co‐activity domains. Synopsis: Human individual variation is used to characterize the co‐regulatory processes underlying domain co‐activity. Systematic quantification of their effect sizes reveals transcription factor expression as the main determinant of co‐activity. A novel transcriptional decomposition approach for extracting the portion of gene expression explained by genomic positioning, referred to as co‐activity, reveals domains of co‐activity covering the majority of expressed genes.Leveraging human individual variation in expression identifies regulatory mechanisms explaining variability in co‐activity domains and allows for a careful quantification of their relative effect sizes.Variation in transcription factor expression explains the largest proportion of variation in co‐activity, indicating that distal trans effects contribute more than local genetic variation to individual variation in co‐activity domains. [ABSTRACT FROM AUTHOR]

The structure and functioning of the brain are lateralized—the right hemisphere processes unexpected stimuli and controls spontaneous behavior, while the left deals with familiar stimuli and routine responses. Hemispheric dominance, the predisposition of an individual using one hemisphere over the other, may lead to behavioral differences; particularly, an individual may be programed to act in a certain way concerning hemispheric dominance. Hand preference is a robust estimator of hemispheric dominance in primates, as each hemisphere controls the opposing side of the body. Studies have found links between hand preference and the exhibition of behaviors in contexts such as exploring and manipulating objects. However, little is known whether hand preference predicts behavioral variations in other ecologically relevant contexts like predation. We investigated the relationship between hand preference and behavioral responses to two types of predator models in captive Barbary macaques (Macaca sylvanus) (n = 22). Besides, a nonpredator novel object was included as control. We found 91% of the macaques to be lateralized with no group‐level bias. A higher rate of tension and focus (behavioral response) behavior was found in predator contexts than in the novel object condition. Unlike their right‐hand counterparts, individuals with a strong left‐hand preference elicited frequent focus and tension behavior toward the predator models. Additionally, the behavioral response varied with predator type. We also found an interaction effect between hand preference and predator type. Our study suggests that hand preference can reliably predict behavioral variations in the context of potential predation. While these results are consistent with lateralized brain function, indicating lateralization a neural mechanism of behavioral variation, the interaction effect between hand preference and predator type elucidates the importance of context‐specificity when investigating laterality noninvasively. Future research on other nonhuman primates using the current framework may provide insights into the evolution of laterality and underlying behavioral predispositions. Research highlights: Hand preference is an indicator of hemispheric dominance, especially in nonhuman primates.We investigated the relationship between hand preference and behavioral response in captive Barbary macaques using an ecologically relevant context.Our findings suggest a potential role of brain lateralization in behavioral predisposition using a noninvasive framework. [ABSTRACT FROM AUTHOR]

Alongside significant gains in our understanding of the human mind, research in Cognitive Science has produced substantial evidence that the details of cognitive processes vary across cultures, contexts, and individuals. In order to arrive at a more nuanced account of the workings of the human mind, in this letter we argue that one challenge for the future of Cognitive Science is the integration of this evidence of variation with findings which can be generalized. [ABSTRACT FROM AUTHOR]

Research on multilingual speakers is often compared to monolingual baselines which are commonly treated as if they were homogeneous across speakers. Despite recent research showing that this homogeneity does not hold, these practices reproduce native-speakerism and monolingualism. Heritage language research, which established itself in the past two decades, is no exemption. Focusing on three predefined linguistic groups, namely Turkish speakers which are framed as monolingual in Turkey as well as two heritage bilingually framed groups in Germany and the USA, we ask: (1) Do heritage speakers of Turkish produce more discourse and fluency markers (FMs) than monolingual speakers? (2) Are the groups homogeneous, or is there wide variation between speakers across groups? We focus on the variation between and within groups using Bayesian Linear Regression with a multilevel model for speakers and heritage groups. Our findings confirm that the use of discourse and FMs is largely defined through individual variation, and not through the belonging to a certain speaker group. By focusing on variation across groups rather than between groups, our study design supports the growing body of literature that questions common heritage language research practices of today and shows alternative paths to understanding heritage grammars. [ABSTRACT FROM AUTHOR]