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Prior work has found links between consistency in toddler handedness for the fine motor skill role-differentiated bimanual manipulation (RDBM), and language development at 2 and 3 years of age. The current study investigated whether consistency in handedness from 18 to 24 months (N = 90) for RDBM predicts receptive and expressive language abilities assessed using the Preschool Language Scales 5th edition (PLS-5) at 5 years old. Latent class growth analyses identified 3 stable RDBM hand preference trajectories: a left hand preference with moderate right hand use (left-moderate right), a right hand preference with moderate left hand use (right-moderate left), and a right hand preference with only mild left hand use (right-mild left). At 5 years of age, children with a right-mild left handedness trajectory as toddlers scored significantly higher on receptive and expressive language abilities compared to children with a left-moderate right hand preference. Children with a right-mild left hand preference for RDBM also scored significantly higher on receptive language abilities compared to children with a right-moderate left RDBM hand preference. Children with left-moderate right and children with a right-moderate left hand preference for RDBM as toddlers did not differ in receptive or expressive language abilities at 5 years. Results indicate that individual differences in hand preference consistency for fine motor skill in toddlerhood have cascading effects on language outcomes into the preschool years.

Background: Parents' conceptualizations of adulthood for their emerging adults with Down syndrome have the potential to impact the transition planning process as families prepare for life after graduation. Aims: This study aimed to explore parent perceptions of the meaning of adulthood for their emerging adults with Down syndrome. Methods: In this qualitative study, we interviewed 11 parents of emerging adults with Down syndrome using phenomenological methodology and analysed these data using thematic analysis. Results: Three topics emerged: (1) Parents' constructions of the meaning of adulthood; (2) Parents' perceptions about the transition to adulthood; and (3) Parents' perceptions of current adult life skills. Ten themes arose out of these topics. Conclusions: Parents expressed ambivalence about the meaning of adulthood for their emerging adults with Down syndrome, sharing that in some ways they were adults and in others they were not. The meaning of adulthood was closely tied to obtained skills, particularly those related to personal safety. [ABSTRACT FROM AUTHOR]

How infants engage with objects changes dramatically over the first year of life. While some infants exhibit a consistent hand preference for acquiring objects during this period, others have no identifiable preference. The goal of this study was to test whether lateralization confers an advantage in the development of early object management skills. We examined whether lateralized infants show different rates of growth in how they interact with multiple objects as compared to infants without a hand preference. In a longitudinal study consisting of seven monthly visits from 6 to 12 months, 303 infants were assessed for their hand preference and object management skill (i.e., holding up to three objects). Group-Based Trajectory Modeling (GBTM) identified the following three hand preference trajectory groups: Left, Right, and No Preference (NP). A Hierarchical Generalized Linear Model (HGLM) with the NP infants as the reference group for statistical comparisons revealed that while all the infants showed similar trends in their object management skills over time, the lateralized infants had an advantage over the non-lateralized infants. The infants in the Right and Left groups transitioned from holding one to two objects more quickly relative to the NP infants. Further research is needed to determine if this early object skill advantage cascades to a more complex handling of multiple objects. [ABSTRACT FROM AUTHOR]

Prior studies found that hand preference trajectories predict preschool language outcomes. However, this approach has been limited to examining bimanual manipulation in toddlers. It is not known whether hand preference during infancy for acquiring objects (i.e., reach‐to‐grasp) similarly predicts childhood language ability. The current study explored this motor‐language developmental cascade in 90 children. Hand preference for acquiring objects was assessed monthly from 6 to 14 months, and language skill was assessed at 5 years. Latent class growth analysis identified three infant hand preference classes: left, early right and late right. Infant hand preference classes predicted 5‐year language skills. Children in the left and early right classes, who were categorized as having a consistent hand preference, had higher expressive and receptive language scores relative to children in the inconsistent late right class. Consistent classes did not differ from each other on language outcomes. Infant hand preference patterns explained more variance for expressive and receptive language relative to previously reported toddler hand preference patterns, above and beyond socio‐economic status. Results suggest that hand preference, measured at different time points across development using a trajectory approach, is reliably linked to later language. Highlights: Hand preference trajectories reliably predict preschool language above and beyond SES.Infants with a consistent hand preference for reaching had greater language skills at 5 years.Infant hand preference explained more variance in language than toddler hand preference. [ABSTRACT FROM AUTHOR]

A defining feature of most primates is a hand with five fingers. Spider monkeys are an exception because they have four fingers and no thumb. Despite the prevalence of reach-to-grasp research in primates, it is not known how the lack of a thumb affects reaching and grasping in spider monkeys. Drawing on patterns that have been well described in human adults, human infants, and other nonhuman primates, this study characterized prehension in Colombian spider monkeys (Ateles fusciceps rufiventris). Monkeys reached for two differently sized food objects and reaches were digitized offline for two-dimensional kinematic analysis. Grasp strategy was coded from video as preshaped when the hand was adjusted to grasp the food before contact, or not preshaped when the hand was adjusted to grasp the food after contact. Monkeys exhibited variability in reach smoothness that contrasted with the typical pattern seen in other adult primates and instead resembled the pattern observed in human infants. Monkeys anticipated the object to be grasped approximately half of the time. Reaches where the hand was preshaped to the object were smoother than reaches where the hand was adjusted to grasp after object contact. For the small object, reaches with preshaping were straighter than reaches without preshaping. Results are the first evidence of kinematic signatures for reach-to-grasp actions in spider monkeys. [ABSTRACT FROM AUTHOR]

I argue that the future of comparative cognition is not what we study but how we study it. I suggest that future scientists should ask questions from a developmental framework. I review common challenges in longitudinal research that scientists in comparative cognition encounter. Leveraging emerging large-scale collaborations within and across taxa (i.e., big team science) can enable us to overcome these challenges to answer how cognitive abilities develop. This appeal for a developmental lens will facilitate interdisciplinary discussion in comparative cognition. [ABSTRACT FROM AUTHOR]

Researchers have long been interested in the relationship between handedness and language in development. However, traditional handedness studies using single age groups, small samples, or too few measurement time points have not capitalized on individual variability and may have masked 2 recently identified patterns in infants: those with a consistent hand-use preference and those with an inconsistent preference. In this study, we asked whether a consistent infant hand-use preference is related to later language ability. We assessed handedness in 38 children at monthly intervals from 6-14 months (infant visits) and again from 18-24 months (toddler visits). We found that consistent right-handedness during infancy was associated with advanced language skills at 24 months, as measured by the Bayley Scales of Infant and Toddler Development (Bayley-III; Bayley, 2006). Children who were not lateralized as infants but who became right-handed or left-handed as toddlers had typical language scores. Neither timing nor direction of lateralization was related to cognitive or general motor skills. This study builds on previous literature linking right-handedness and language during the first 2 years of life.

Object play is essential for infant learning, and infants spend most of their day with objects. Young infants learn about objects and their properties through multimodal exploration facilitated by caregivers. They figure out how to transport their hands to where objects are, and how to grasp objects in increasingly complex ways. Building on earlier experiences, they learn how to use their hands collaboratively to act on objects, and how to use objects to act on other objects in instrumental ways. These changes in how infants use their hands occur during the most rapid period of motor development and may have important downstream implications for other domains. Recent research findings have established the importance of effective fine motor skills for later academic skills, yet our understanding of the factors that influence the early development of hand skills is sparse at best. Latest research on reaching, grasping, object manipulation, hands collaboration, and tool use is reviewed and connections among these developments are explained from the perspective of developmental cascades. This article is categorized under:Psychology > Motor Skill and PerformancePsychology > Development and Aging [ABSTRACT FROM AUTHOR]

Background: Children with Down syndrome (DS) typically have motor and language needs. Improving function is a shared goal for the rehabilitation therapy team, however physical therapy, occupational therapy, and speech-language pathology professionals treat patients differently. This difference in care may mask developmental cascades whereby changes in one domain (e.g., motor) can have seemingly unexpected effects on another domain (e.g., language). Objective: This scoping review identified papers where motor and language data have been reported together in children with DS and reinterpreted findings from a developmental cascades lens. Design: Online databases were used to identify 413 papers published before October 2021 from which 33 papers were retained that reported both motor (gross and/or fine) and language (expressive and/or receptive) data in individuals with DS with a chronological age of 0-18 years. Results: The majority of papers (79%) that reported motor and language data in children with DS did not examine their link, while 12% analyzed motor-language links, but using a cross-sectional or retrospective design. Only three papers (9%) utilized a longitudinal design to examine predictive links. Conclusion: Motor functioning and language functioning have often been reported together, but not analyzed together, in studies of children with DS. The few studies that did analyze motor-language links largely replicated findings from other developmental populations where motor gains were positively linked to language gains. Analyzing links between domains when such data is available is needed to fully characterize developmental cascades in DS and may have broad clinical implications. [ABSTRACT FROM AUTHOR]

McCarty and colleagues (1999) developed the elevated spoon task to measure motor planning in human infants. In this task, a spoon containing food was placed on an elevated apparatus that supported both ends of the spoon. The handle was oriented to the left or right on different trials. We presented naive adult rhesus monkeys (Macaca mulatta) with the elevated spoon problem, and observed how monkeys learned the affordances of spoons over sessions. Strikingly, monkeys developed two different strategies for efficient spoon transport in just 12 to 36 trials. In subsequent testing with a novel double bowl spoon approximately 1 year later, monkeys demonstrated that they were attending to the baited spoon bowl and continued to select efficient grips for transporting the spoon. Monkey data were contrasted with previous studies in human infants using a perception-action perspective in an effort to understand the fundamentals of tool use and motor planning that may be common in the development of these abilities across species and their origins in human behavior.

Unlike in human research, infants are poorly represented in the literature on nonhuman primate laterality. Studies have traditionally measured adults, a trend captured by prior reviews. The extent of the knowledge gaps related to laterality measured early in the lifespan is unknown. As a starting point, this systematic review examined the evidence on behavioral laterality across the first year of life in nonhuman primates using the PRISMA guidelines. The inclusion criteria were at least one measure of behavioral laterality in at least one subject < 1 year old. Database searches were conducted in PsycINFO, PubMed, and OVID Medline using the filterNHP search builder tool, and additional records were identified through citation searching. Two independent reviewers screened abstracts and full texts; 47 articles were retained (0 prosimian, 6 platyrrhine, 27 catarrhine, and 14 ape studies). Macaca and Pan were overrepresented. Nipple preference was the most-studied behavior, followed by hand preference. Modifying how data are collected and analyzed will increase developmental rigor in primate studies. To facilitate comparisons with the human infant literature, we suggest measuring a behavior more than once to test for change or continuity in preference over time and measuring different behaviors at different timepoints to test for potential developmental cascades. [ABSTRACT FROM AUTHOR]

Stacking is a hallmark of fine motor skill development and requires skilled hand use. One mechanism for children to gain manual proficiency involves establishing a hand preference that creates practice differences between the hands as the preferred hand is used more often and in different ways than the other. Prior work found that stacking skill emerged earlier for infants with an identifiable hand preference. However, it is not known how hand preference relates to later toddler stacking performance. This study examined the effects of early hand preference (infant pattern), concurrent hand preference (toddler pattern), and consistent hand preference (infant to toddler pattern) on toddler stacking skills. Sixty‐one toddlers, whose hand preferences as infants were known, were assessed for their toddler hand preference and their stacking skill across 7 monthly visits from 18 to 24 months of age. Using multilevel Poisson longitudinal analysis, children with hand preferences that were consistent across both infancy and toddlerhood were more successful at stacking, compared to those with inconsistent preferences across the infant and toddler periods. Thus, consistency of hand preferences during the first 2 years likely contributes toward individual differences in the development of fine motor skills. [ABSTRACT FROM AUTHOR]

Handedness is part of our everyday lives, but where does it come from? Researchers studying nonhuman primates and young children have approached this question from different perspectives—evolutionary and developmental, respectively. Their work converges on the conclusion that measurement matters in the science of handedness. Coming to a consensus on assessment will guide future research into the origins of handedness. A candidate behavior for promoting multidisciplinary comparison is role-differentiated bimanual manipulation. [ABSTRACT FROM AUTHOR]

Questionnaires are commonly used to measure handedness. However, popular measures do not capture hand preference by skill type, thus reducing handedness to a single dimension. An exception is the Home Handedness Questionnaire (HHQ), an action-based measure developed initially for children, which measures skills across two dimensions of handedness: unimanual actions and role differentiated bimanual manipulation (RDBM). The goal of the current study was to confirm the factor structure of the HHQ in a large sample of adults (N = 1051). A secondary goal was to measure RDBM hand preference in adults. To further validate the HHQ, participants also completed the Edinburgh Handedness Inventory (EHI). Confirmatory factor analysis verified the two-factor structure of the HHQ, and a one-factor solution was replicated for the EHI. Individuals that were classified as consistent on the EHI had stronger preferences for unimanual and RDBM hand use on the HHQ. Right hand patterning was reduced for RDBM compared to unimanual on the HHQ, and the EHI. The HHQ was found to be reliable and valid against the EHI. The HHQ offers researchers a tool to examine individual differences across manual skills that comprise the neuropsychological phenomenon handedness, and to more broadly examine laterality patterns with respect to cognition. [ABSTRACT FROM AUTHOR]

The emerging field of network science has demonstrated that an individual's connectedness within their social network has cascading effects to other dimensions of life. Like humans, spider monkeys live in societies with high fission–fusion dynamics, and are remarkably social. Social network analysis (SNA) is a powerful tool for quantifying connections that may vary as a function of initiating or receiving social behaviors, which has been described as shifting social roles. In primatology, the SNA literature is dominated by work in catarrhines, and has yet to be applied to the study of development in a platyrrhine model. Here, SNA was utilized in combination with R‐Index social role calculation to characterize social interaction patterns in juvenile and adult Colombian spider monkeys (Ateles fusciceps rufiventris). Connections were examined across five behaviors: embrace, face‐embrace, grooming, agonism, and tail‐wrapping from 186 hr of observation and four network metrics. Mann–Whitney U tests were utilized to determine differences between adult and juvenile social network patterns for each behavior. Face‐embrace emerged as the behavior with different network patterns for adults and juveniles for every network metric. With regard to social role, juveniles were receivers, not initiators, for embrace, face‐embrace, and grooming (ps <.05). Network and social role differences are discussed in light of social development and aspects of the different behaviors. Research Highlights: Juvenile spider monkeys occupy peripheral positions in social networks for the social behaviors embrace, face‐embrace, and tail‐wrapping.Juvenile spider monkeys do not significantly differ from adults in network position for grooming or agonism.Our findings suggest that juveniles may be integrated in adult grooming and agonism networks, but may not yet be integrated in embrace networks due the complexity of learning socio‐behavioral traditions and managing social risk. [ABSTRACT FROM AUTHOR]

Researchers have utilized reaching paradigms to measure infant handedness for more than a century. However, methods vary widely. Recent research has identified that the number of trials used in assessment is critical with the recommendation that at least 15 trials are necessary to reliably classify infants into handedness categories via statistical cutoffs. As a first step towards establishing best practices for the field, we identified, categorized, and synthesized findings according to trial number from studies that utilized reaching to index handedness in infants across the first two years of life using PRISMA guidelines. Database searches were conducted in PsycINFO, PubMed, and Ovid MEDLINE®. All articles published through May 2018 were included. Additional records were identified through other sources. After removing duplicates, 1,116 records were screened using the online software program Abstrackr. Of these records, 125 full-text articles were further assessed for eligibility, and 87 articles were included in the qualitative synthesis. Results revealed that the majority of papers published since 1890 (70%) do not meet the 15-trial minimum criterion for statistically reliable measurement of infant handedness. Broad themes from articles meeting the measurement criterion and implications for future research are discussed. [ABSTRACT FROM AUTHOR]

Background: Changes in motor development provide children with new learning opportunities to interact with objects, their environment, and with caregivers. Previous research finds that both gross and fine motor skills are predictive of later language outcomes across early infancy and childhood. However, gross and fine motor skills afford different types of interactions. Thus, gross and fine motor skills may potentially differ in the developmental trajectories through which cascading changes in language may occur. The aim of the present study was to investigate whether there are differences in the predictive capacities of gross and fine motor skills toward language outcomes across infancy and early childhood in typical development. Method: A systematic review of existing literature on motor-language cascades was conducted in across studies measuring gross and/or fine motor and language development in children from 0 to 5 years old. Searches were conducted in PsycINFO, PubMed, and MEDLINE. Keywords used were a combination of "gross motor," "fine motor," "motor performance," "motor development," or "psychomotor development" along with "language," "language development," or "communication skills." Two independent reviewers screened abstracts and full texts based on inclusion and exclusion criteria. Results: A total of 23 articles were retained. Of these, seven studies measured only gross motor skills, four studies measured only fine motor skills, and 12 studies measured both gross and fine motor skills in the same study. Studies used a variety of measures to assess gross motor skills, fine motor skills, and language development (e.g., parent report, in lab observations, standardized assessment), and findings varied based on analyses used. Results demonstrated that both gross and fine motor skills are related to language outcomes, but due to a smaller amount of studies testing fine motor skills, conclusions regarding whether one is more important for language outcomes cannot be drawn. Conclusions: We conclude that both gross and fine motor skills help foster language development from infancy to early childhood. Limitations regarding current knowledge regarding the mechanisms that underlie motor-language cascades are discussed, as well as the need for more studies on fine motor skills. [ABSTRACT FROM AUTHOR]

While handedness questionnaires are widely used in adults, there is no comparable measure designed specifically for children. The current study developed the Home Handedness Questionnaire (HHQ), a new measure for preschoolers administered by parents using common household items. The HHQ has two scales that distinguish action types typically combined on other measures: actions performed with only the right or left hand (i.e., unimanual, such as holding a toothbrush), and actions performed with one hand holding the object for the other hand's action (i.e., role-differentiated bimanual manipulation or RDBM, such as unscrewing a lid from a jar). The HHQ was able to detect right preference, left preference, and no preference for unimanual and RDBM actions in a proof of concept study in 3-year-olds (N = 64). The HHQ identified a majority of children as right-handed, but was also sensitive to variability in direction across skill types. Approximately one-quarter of children in the sample had mixed preferences for the two types of manual skills, suggesting that for a subgroup of children, hand use patterns may still be undergoing change. Suggestions for refining the HHQ are discussed. Overall, the HHQ is a promising multidimensional parent-led tool for assessing preschool handedness. [ABSTRACT FROM AUTHOR]

Early in development, children explore and combine objects in increasingly complex ways. One manual skill, object construction, represents a major shift in how objects are explored relative to other objects. Despite recent connections with cognitive functioning such as spatial skills, the development of object construction ability has rarely been studied and its trajectory has not been adequately described. The purpose of this study was to describe the development of three types of object construction (stacking, nesting, and affixing) across 5 monthly infant visits and 7 monthly toddler visits using a longitudinal design and a large sample size. Infants (10–14 months, n = 131) and toddlers drawn from the infant sample (18–24 months, n = 65) were given sets of age‐appropriate toys each of which elicited at least one type of constructive play. We described success at different construction tasks and identified trends for construction skill for infant and toddler development using multilevel modeling. We found that each of the three construction actions developed in unique ways across the 10‐ to 24‐month period. Infant construction skill predicted the development of toddler skill, but toddler construction skill diverged from infant trajectories. We discuss the role of combination strategies in the development of object construction skill and how object construction could be related to other domains of development. [ABSTRACT FROM AUTHOR]

The primary goal of this study was to examine the relations between limb control and handedness in adults. Participants were categorized as left or right handed for analyses using the Edinburgh Handedness Inventory. Three-dimensional recordings were made of each arm on two reach-to-place tasks: adults reached to a ball and placed it into the opening of a toy (fitting task), or reached to a Cheerio inside a cup, which they placed on a designated mark after each trial (cup task). We hypothesized that limb control and handedness were related, and we predicted that we would observe side differences favoring the dominant limb based on the dynamic dominance hypothesis of motor lateralization. Specifically, we predicted that the dominant limb would be straighter and smoother on both tasks compared with the nondominant limb (i.e., right arm in right-handers and left arm in left-handers). Our results only partially supported these predictions for right-handers, but not for left-handers. When differences between hands were observed, the right hand was favored regardless of handedness group. Our findings suggest that left-handers are not reversed right-handers when compared on interlimb kinematics for reach-to-place tasks, and reaffirm that task selection is critical when evaluating manual asymmetries. [ABSTRACT FROM AUTHOR]

A growing body of work suggests that early motor experience affects development in unexpected domains. In the current study, children's hand preference for role-differentiated bimanual manipulation (RDBM) was measured at monthly intervals from 18 to 24 months of age ( N = 90). At 3 years of age, children's language ability was assessed using the Preschool Language Scales 5th edition (PLS™-5). Three distinct RDBM hand preference trajectories were identified using latent class growth analysis: (1) children with a left hand preference but a moderate amount of right hand use; (2) children with a right hand preference but a moderate amount of left hand use; and (3) children with a right hand preference and only a mild amount of left hand use. Stability over time within all three trajectories indicated that children did not change hand use patterns from 18 to 24 months. Children with the greatest amount of preferred (i.e., right) hand use demonstrated higher expressive language scores compared to children in both trajectories with moderate levels of non-preferred hand use. Children with the greatest amount of right hand use also had higher scores for receptive language compared to children with a right hand preference but moderate left hand use. Results support that consistency in handedness as measured by the amount of preferred hand use is related to distal language outcomes in development. [ABSTRACT FROM AUTHOR]

Side biases observed in behavior are thought to reflect underlying asymmetric brain function or hemispheric specialization. Previous work in multiple species identified left side biases (associated with the right hemisphere) for processing social behavior. In highly social species such as primates, many behaviors may be categorized as social, yet differences between such behaviors have not been examined as a test of asymmetric brain function. Using Colombian spider monkeys ( Ateles fusciceps rufiventris), we observed lateral positioning during two types of behaviors widely categorized as social affiliative: embracing and grooming, and identified a left bias for embracing, but not grooming. Our findings partially support prior research in hemispheric specialization, but suggest that there may be differences between social behaviors that drive specialization. We discuss these results in light of current theory on hemispheric specialization and highlight differences between embracing and grooming. [ABSTRACT FROM AUTHOR]

Background and Objectives: Extreme cardiovascular reactions to psychological stress have been associated with traumatic life experiences. Previous studies have focused on the occurrence or frequency of abuse rather than type of abuse. We examined how occurrence, frequency, and the type of abuse history are related to cardiovascular reactivity (CVR) to acute psychological stress.Design: The study consisted of between group and continuous analyses to examine the association between occurrence, type, and frequency of abuse with cardiovascular reactions to acute psychological stress.Methods: Data from 64 participants were collected. Heart rate, systolic blood pressure, and diastolic blood pressure were measured at baseline and during a standard mental arithmetic stress task.Results: Individuals who experienced abuse showed diminished CVR to acute psychological stress; this was driven specifically by the history of sexual abuse. Frequency of abuse did not relate to stress reactions.Conclusions: These findings accord with previous work suggesting a relationship between traumatic life experience and hypoarousal in physiological reactivity and extend previous findings by suggesting the relationship may be driven by sexual abuse. [ABSTRACT FROM AUTHOR]

The emergence of new motor skills, such as reaching and walking, dramatically changes how infants engage with the world socially and cognitively. Several examples of how motor experience can cascade into cognitive and social development have been documented, yet a significant knowledge gap remains in our understanding of whether these observed behavioral changes are accompanied by underlying neural changes. We propose that electroencephalography (EEG) measures such as power, coherence, and mu desynchronization are optimal tools to quantify motor experience in the infant brain. In this mini-review, we will summarize existing infant research that has separately assessed the relation between motor, cognitive, or social development with coherence, power, or mu desynchronization. We will discuss how the reviewed neural changes seen in seemingly separate developmental domains may be linked based on existing behavioral evidence. We will further propose that power, coherence, and mu desynchronization be used in research exploring the links between motor experience and cognitive and social development. [ABSTRACT FROM AUTHOR]

Decades of research on the hand use patterns of nonhuman primates can be aptly summarized by the following phrase: measurement matters. There is a general consensus that simple reaching is a poor indicator of handedness in most species, while tasks that constrain how the hands are used elicit individual, and in some cases, population-level biases. The TUBE task has become a popular measure of handedness, although there is variability in its administration across studies. The goal of this study was to investigate whether TUBE performance is affected by tube diameter, with the hypothesis that decreasing tube diameter would increase task complexity, and therefore the expression of handedness. We predicted that hand preference strength, but not direction, would be affected by tube diameter. We administered the TUBE task using a 1.3 cm tube to Colombian spider monkeys, and compared their performance to a previous study using a larger 2.5 cm diameter tube. Hand preference strength increased significantly on the smaller diameter tube. Hand preference direction was not affected. Notably, spider monkeys performed the TUBE task using a single digit, despite the longstanding view that this species has poor dexterity. We encourage investigators who use the TUBE task to carefully consider the diameter of the tube used in testing, and to report digit use consistently across studies. In addition, we recommend that researchers who cannot use the TUBE task try to incorporate the key features from this task into their own species appropriate measures: bimanual coordination and precise digit use. Am. J. Primatol. 77:1253-1262, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The authors discuss the blueprint in studying the role of the hands by infants in manipulating or stabilizing objects. They cite the studies that found that role-differentiated bimanual manipulation (RDBM) hand preference emerges with a trend favoring the right hand. The authors believe that RDBM constrains the roles of the hands which elicit a measurable asymmetry for the manipulating hand as the preferred hand for RDBM actions.

BackgroundCurrent technology innovations, such as wearables, have caused surprising reactions and feelings of deep connection to devices. Some researchers are calling mobile and wearable technologies cognitive prostheses, which are intrinsically connected to individuals as if they are part of the body, similar to a physical prosthesis. Additionally, while several studies have been performed on the phenomenology of receiving and wearing a physical prosthesis, it is unknown whether similar subjective experiences arise with technology. ObjectiveIn one of the first qualitative studies to track wearables in a longitudinal investigation, we explore whether a wearable can be embodied similar to a physical prosthesis. We hoped to gain insights and compare the phases of embodiment (ie, initial adjustment to the prosthesis) and the psychological responses (ie, accept the prosthesis as part of their body) between wearables and limb prostheses. This approach allowed us to find out whether this pattern was part of a cyclical (ie, period of different usage intensity) or asymptotic (ie, abandonment of the technology) pattern. MethodsWe adapted a limb prosthesis methodological framework to be applied to wearables and conducted semistructured interviews over a span of several months to assess if, how, and to what extent individuals come to embody wearables similar to prosthetic devices. Twelve individuals wore fitness trackers for 9 months, during which time interviews were conducted in the following three phases: after 3 months, after 6 months, and at the end of the study after 9 months. A deductive thematic analysis based on Murray’s work was combined with an inductive approach in which new themes were discovered. ResultsOverall, the individuals experienced technology embodiment similar to limb embodiment in terms of adjustment, wearability, awareness, and body extension. Furthermore, we discovered two additional themes of engagement/reengagement and comparison to another device or person. Interestingly, many participants experienced a rarely reported phenomenon in longitudinal studies where the feedback from the device was counterintuitive to their own beliefs. This created a blurring of self-perception and a dilemma of “whom” to believe, the machine or one’s self. ConclusionsThere are many similarities between the embodiment of a limb prosthesis and a wearable. The large overlap between limb and wearable embodiment would suggest that insights from physical prostheses can be applied to wearables and vice versa. This is especially interesting as we are seeing the traditionally “dumb” body prosthesis becoming smarter and thus a natural merging of technology and body. Future longitudinal studies could focus on the dilemma people might experience of whether to believe the information of the device over their own thoughts and feelings. These studies might take into account constructs, such as technology reliance, autonomy, and levels of self-awareness.

ABSTRACT We propose a developmental process which may link the development of handedness with the development of hemispheric specialization for speech processing. Using Arbib's proposed sequence of sensorimotor development of manual skills and gestures (that he considers to be the basis of speech gestures and proto-language), we show how the development of hand-use preferences in proto-reaching skills concatenate into object acquisition skills and eventually into role-differentiated bimanual manipulation skills (that reflect interhemispheric communication and coordination). These latter sensorimotor skills might facilitate the development of speech processing via their influence on the development of tool-using and object management abilities. © 2013 Wiley Periodicals, Inc. Dev Psychobiol 55: 608-620, 2013. [ABSTRACT FROM AUTHOR]

We show that handedness is a product of a multifaceted biosocial developmental process that begins prenatally and continues into adulthood. Although right-handedness predominates, handedness varies continuously across the population. Therefore, our phrase "multiple trajectories"refers to both differences in developmental pathways that can lead to similarities in handedness and similarities in pathways that can lead to differences in handedness. The task for the researcher is to identify how, when, and for what actions the trajectory of handedness development can be maintained or changed for an individual. Given the complexity of these developmental pathways, it is likely that the asymmetric sensorimotor activity that occurs during the development of handedness influences other hemispheric variations in neural processing. Indeed, researchers have investigated how handedness relates to cognitive, social, and emotional functioning because handedness represents different patterns of hemispheric specialization. Although the story of handedness development is not complete, it is well worth pursuing because it makes the development of brain-behavior relations more transparent, especially for hemispheric differences in function. [ABSTRACT FROM AUTHOR]

Kinematic studies of reaching in human infants using two-dimensional (2-D) and three-dimensional (3-D) recordings have complemented behavioral studies of infant handedness by providing additional evidence of early right asymmetries. Right hand reaches have been reported to be straighter and smoother than left hand reaches during the first year. Although reaching has been a popular measure of handedness in primates, there has been no systematic comparison of left and right hand reach kinematics. We investigated reaching in infant rhesus monkeys using the 2-D motion analysis software MaxTRAQ Lite+ (Innovision Systems). Linear mixed-effects models revealed that left hand reaches were smoother, but not straighter, than right hand reaches. An early left bias matches previous findings of a left hand preference for reaching in adult rhesus monkeys. Additional work using this kind of kinematic approach will extend our understanding of primate handedness beyond traditional studies measuring only frequency or bouts of hand use. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 54:460-467, 2012. [ABSTRACT FROM AUTHOR]