An update of the development of motor behavior.

This primer describes research on the development of motor behavior. We focus on infancy when basic action systems are acquired-posture, locomotion, manual actions, and facial actions-and we adopt a developmental systems perspective to understand the causes and consequences of developmental change. Experience facilitates improvements in motor behavior and infants accumulate immense amounts of varied everyday experience with all the basic action systems. At every point in development, perception guides behavior by providing feedback about the results of just prior movements and information about what to do next. Across development, new motor behaviors provide new inputs for perception. Thus, motor development opens up new opportunities for acquiring knowledge and acting on the world, instigating cascades of developmental changes in perceptual, cognitive, and social domains. This article is categorized under: Cognitive Biology > Cognitive Development Psychology > Motor Skill and Performance Neuroscience > Development.

Longitudinal relations between independent walking, body position, and object experiences in home life.

How do age and the acquisition of independent walking relate to changes in infants' everyday experiences? We used a novel ecological momentary assessment (EMA) method to gather caregiver reports of infants' restraint, body position, and object holding via text messages sparsely sampled across multiple days of home life at 10, 11, 12, and 13 months of age. Using data from over 4,000 EMA samples from N = 62 infants recruited from across the United States and sampled longitudinally, we measured changes in the base rates of different activities in daily life. With age, infants spent more time unrestrained. With the onset of walking, infants spent less time sitting and prone and more time upright. Although rates of object holding did not change with age or walking ability, we found that infants who can walk hold objects more often in an upright position compared with nonwalkers. We discuss how accurately measuring changes in lived experiences serves to constrain theories about developmental mechanisms. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Long-form recording of infant body position in the home using wearable inertial sensors.

Long-form audio recordings have had a transformational effect on the study of infant language acquisition by using mobile, unobtrusive devices to gather full-day, real-time data that can be automatically scored. How can we produce similar data in service of measuring infants' everyday motor behaviors, such as body position? The aim of the current study was to validate long-form recordings of infant position (supine, prone, sitting, upright, held by caregiver) based on machine learning classification of data from inertial sensors worn on infants' ankles and thighs. Using over 100 h of video recordings synchronized with inertial sensor data from infants in their homes, we demonstrate that body position classifications are sufficiently accurate to measure infant behavior. Moreover, classification remained accurate when predicting behavior later in the session when infants and caregivers were unsupervised and went about their normal activities, showing that the method can handle the challenge of measuring unconstrained, natural activity. Next, we show that the inertial sensing method has convergent validity by replicating age differences in body position found using other methods with full-day data captured from inertial sensors. We end the paper with a discussion of the novel opportunities that long-form motor recordings afford for understanding infant learning and development.

Age differences in orienting to faces in dynamic scenes depend on face centering, not visual saliency.

The current study investigated how infants (6-24 months), children (2-12 years), and adults differ in how visual cues-visual saliency and centering-guide their attention to faces in videos. We report a secondary analysis of Kadooka and Franchak (2020), in which observers' eye movements were recorded during viewing of television clips containing a variety of faces. For every face on every video frame, we calculated its visual saliency (based on both static and dynamic image features) and calculated how close the face was to the center of the image. Results revealed that participants of every age looked more often at each face when it was more salient compared to less salient. In contrast, centering did not increase the likelihood that infants looked at a given face, but in later childhood and adulthood, centering became a stronger cue for face looking. A control analysis determined that the age-related change in centering was specific to face looking; participants of all ages were more likely to look at the center of the image, and this center bias did not change with age. The implications for using videos in educational and diagnostic contexts are discussed.

Beyond screen time: Using head-mounted eye tracking to study natural behavior.

Head-mounted eye tracking is a new method that allows researchers to catch a glimpse of what infants and children see during naturalistic activities. In this chapter, we review how mobile, wearable eye trackers improve the construct validity of important developmental constructs, such as visual object experiences and social attention, in ways that would be impossible using screen-based eye tracking. Head-mounted eye tracking improves ecological validity by allowing researchers to present more realistic and complex visual scenes, create more interactive experimental situations, and examine how the body influences what infants and children see. As with any new method, there are difficulties to overcome. Accordingly, we identify what aspects of head-mounted eye-tracking study design affect the measurement quality, interpretability of the results, and efficiency of gathering data. Moreover, we provide a summary of best practices aimed at allowing researchers to make well-informed decisions about whether and how to apply head-mounted eye tracking to their own research questions.

Preschoolers' attention to and learning from on-screen characters that vary by effort and efficiency: An eye-tracking study.

Prior findings are mixed regarding the extent to which children understand others' effort in early childhood. Especially, little is known about how character effort impacts children's selective attention and learning. This study examined preschoolers' visual attention to and learning from two on-screen characters: One character exerting high effort with low efficiency and another character exerting low effort with high efficiency in solving problems successfully. Children between 3.5 and 6.5 years of age (N = 70) watched a video of the two on-screen characters successfully solving problems. Children's eye movements were recorded during viewing. Each of the two on-screen characters consistently displayed either high effort/low efficiency or low effort/high efficiency to solve four problems (familiarization). For the final problem (testing), the two characters exerted the same level of effort as each other and used unique solutions to solve the problem. Children then solved the final problem themselves using real objects. Children could selectively use either character's solution demonstrated in the video. Lastly, children explicitly judged how good the characters were at solving problems. Younger children were more likely to use the solution demonstrated by the character with high effort/low efficiency, whereas older children were more likely to use the solution provided by another character with low effort/high efficiency. Younger children allocated more attention to the high effort/low efficiency character than the low effort/high efficiency character, but this pattern was modified by age such that children's gaze to the low effort/high efficiency character increased with age. Children's explicit credibility judgments did not differ by character or child age. The findings are discussed with respect to preschoolers' understanding of effort and implications for children's learning from screen media.

A Contactless Method for Measuring Full-Day, Naturalistic Motor Behavior Using Wearable Inertial Sensors.

How can researchers best measure infants' motor experiences in the home? Body position-whether infants are held, supine, prone, sitting, or upright-is an important developmental experience. However, the standard way of measuring infant body position, video recording by an experimenter in the home, can only capture short instances, may bias measurements, and conflicts with physical distancing guidelines resulting from the COVID-19 pandemic. Here, we introduce and validate an alternative method that uses machine learning algorithms to classify infants' body position from a set of wearable inertial sensors. A laboratory study of 15 infants demonstrated that the method was sufficiently accurate to measure individual differences in the time that infants spent in each body position. Two case studies showed the feasibility of applying this method to testing infants in the home using a contactless equipment drop-off procedure.

Adapting the coordination of eyes and head to differences in task and environment during fully-mobile visual exploration.

How are eyes and head adapted to meet the demands of visual exploration in different tasks and environments? In two studies, we measured the horizontal movements of the eyes (using mobile eye tracking in Studies 1 and 2) and the head (using inertial sensors in Study 2) while participants completed a walking task and a search and retrieval task in a large, outdoor environment. We found that the spread of visual exploration was greater while searching compared with walking, and this was primarily driven by increased movement of the head as opposed to the eyes. The contributions of the head to gaze shifts of different eccentricities was greater when searching compared to when walking. Findings are discussed with respect to understanding visual exploration as a motor action with multiple degrees of freedom.

Towards a common code for difficulty: Navigating a narrow gap is like memorizing an extra digit.

What makes a task hard or easy? The question seems easy, but answering it has been hard. The only consensus has been that, all else being equal, easy tasks can be performed by more individuals than hard tasks, and easy tasks are usually preferred over hard tasks. Feghhi and Rosenbaum (Journal of Experimental Psychology: Human Perception and Performance, 45, 983-994, 2019) asked whether task difficulty might reflect a single amodal quantity. Based on their subjects' two-alternative forced-choice data from tasks involving choices of tasks with graded physical and mental challenges, the authors showed that the difficulty of passing through a narrow gap rather than a wide gap was psychologically equivalent to memorizing an extra .55 digits. In the present study, we extended this approach by adding new arguments for the hypothesis that task difficulty might reflect a single amodal quantity (inspired by considerations of physics, economics, and the common code hypothesis for the study of perception and action), and we tested narrower gaps than before to see whether we would find a larger equivalent memory-digit. Consistent with our prediction, we obtained a value of .95. We suggest that our multi-modal two-alternative forced-choice procedure can pave the way toward a better understanding of task difficulty.

Head and body structure infants' visual experiences during mobile, naturalistic play.

Infants' visual experiences are important for learning, and may depend on how information is structured in the visual field. This study examined how objects are distributed in 12-month-old infants' field of view in a mobile play setting. Infants wore a mobile eye tracker that recorded their field of view and eye movements while they freely played with toys and a caregiver. We measured how centered and spread object locations were in infants' field of view, and investigated how infant posture, object looking, and object distance affected the centering and spread. We found that far toys were less centered in infants' field of view while infants were prone compared to when sitting or upright. Overall, toys became more centered in view and less spread in location when infants were looking at toys regardless of posture and toy distance. In sum, this study showed that infants' visual experiences are shaped by the physical relation between infants' bodies and the locations of objects in the world. However, infants are able to compensate for postural and environmental constraints by actively moving their head and eyes when choosing to look at an object.

Developmental changes in infants' and children's attention to faces and salient regions vary across and within video stimuli.

Visual attention in complex, dynamic scenes is attracted to locations that contain socially relevant features, such as faces, and to areas that are visually salient. Previous work suggests that there is a global shift over development such that observers increasingly attend to faces with age. However, no prior work has tested whether this shift is truly global, that is, consistent across and within stimuli despite variations in content. To test the global shift hypothesis, we recorded eye movements of 89 children (6 months to 10 years) and adults while they viewed 7 video clips. We measured the extent to which each participant attended to faces and to salient areas for each video. There was no evidence of global age-related changes in attention: Neither feature showed consistent increases or decreases with age. Moreover, windowed analyses within each stimulus video revealed significant moment-to-moment variations in the relation between age and each visual feature (via a bootstrapping analysis). For some time windows, adults looked more often at both feature types compared to infants and children. However, for other time windows, the pattern was reversed-younger participants looked more at faces and salient locations. Lack of consistent directional effects provides strong evidence against the global shift hypothesis. We suggest an alternative explanation: Over development, observers increasingly prioritize when and where to look by learning to track which features are relevant within a scene. Implications for the development of visual attention and children's understanding of screen-based media are discussed. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Calibration of perception fails to transfer between functionally similar affordances.

Prior work shows that the calibration of perception and action transfers between actions depending on their functional similarity: Practising (and thus calibrating perception of) one affordance will also calibrate perception for an affordance with a similar function but not for an affordance with a disparate function. We tested this hypothesis by measuring whether calibration transferred between two affordances for passing through openings: squeezing sideways through doorways without becoming stuck and fitting sideways through doorways while avoiding collision. Participants wore a backpack to alter affordances for passage and create a need for perceptual recalibration. Calibration failed to transfer between the two actions (e.g., practising squeezing through doorways calibrated perception of squeezing but not fitting). Differences between squeezing and fitting affordances that might have required different information for perception and recalibration are explored to understand why calibration did not transfer. In light of these results, we propose a revised hypothesis-calibration transfers between affordances on the basis of both functional and informational similarity.

The ecology of infants' perceptual-motor exploration.

The first goal of this article is to review recent advances in understanding how new motor skills facilitate infants' exploration-the active acquisition of information about their environments. New postural abilities, such as sitting and walking, qualitatively change how infants can learn about objects, places, and people with potential downstream effects on infants' later cognitive and linguistic development. What's missing, however, is a characterization of how new exploratory abilities change infants' everyday experiences. Presumably, changes in opportunities for learning mediate the downstream effects of posture on other developmental achievements. Accordingly, the second goal of this article is to discuss the importance of measuring the ecology of infants' everyday experiences and how they vary.

Development of affordance perception and recalibration in children and adults.

Changes in the body over developmental time (e.g., physical growth) as well as over shorter timescales (e.g., wearing a backpack, carrying a large object) alter possibilities for motor action. How well can children recalibrate their perception of action possibilities to account for sudden changes to body size? The current study compared younger children (4-7 years), older children (8-11 years), and adults as they decided whether they could squeeze through doorways of varying widths. To test for age-related changes in recalibration to modified abilities versus perception of unmodified abilities, half of the participants wore a backpack while making judgments and squeezing through doorways and half did not. Results indicated that judgment accuracy improved with age but that participants had more difficulty when recalibrating to modified abilities. Bias in decision making also changed with age; whereas younger children made riskier decisions by attempting to fit through impossibly small doorways, older children were more cautious. Some particularly cautious participants never generated practice feedback by attempting (and failing) to fit through smaller doorways, which prevented them from recalibrating. Taken together with previous literature, the results of the current study suggest that the development of perception for unmodified versus modified ability proceeds at different rates and depends on the particular motor task.

Changing Opportunities for Learning in Everyday Life: Infant Body Position Over the First Year.

Developmental theories depend on characterizing the input to potential learning mechanisms-infants' everyday experiences. The current study employed a novel ecological momentary assessment (EMA) to measure two aspects of the physical context of those experiences: body position and location. Infant body position was selected because it relates to the development of a variety of other skills. Caregivers of 3-, 6-, 9-, and 12-month-olds reported infants' body position-held, supine, reclined, prone, sitting, or upright-in response to text message notifications over a week to capture infants' experiences across the entire range of their daily activities. Findings revealed a tremendous disparity in the distribution of body position experiences over the first year. Younger infants spend more time held, supine, and reclined, whereas older infants spend more time sitting and upright. Body position experiences differed substantially between same-age infants who possess a motor skill (e.g., ability to sit or walk) compared with those who did not, suggesting that developing motor skills change infants' everyday experiences. Finally, the success of the methodology suggests that similar EMAs might be used to study a wide range of infants' naturalistic experiences.

Gaze in Action: Head-mounted Eye Tracking of Children's Dynamic Visual Attention During Naturalistic Behavior.

Young children's visual environments are dynamic, changing moment-by-moment as children physically and visually explore spaces and objects and interact with people around them. Head-mounted eye tracking offers a unique opportunity to capture children's dynamic egocentric views and how they allocate visual attention within those views. This protocol provides guiding principles and practical recommendations for researchers using head-mounted eye trackers in both laboratory and more naturalistic settings. Head-mounted eye tracking complements other experimental methods by enhancing opportunities for data collection in more ecologically valid contexts through increased portability and freedom of head and body movements compared to screen-based eye tracking. This protocol can also be integrated with other technologies, such as motion tracking and heart-rate monitoring, to provide a high-density multimodal dataset for examining natural behavior, learning, and development than previously possible. This paper illustrates the types of data generated from head-mounted eye tracking in a study designed to investigate visual attention in one natural context for toddlers: free-flowing toy play with a parent. Successful use of this protocol will allow researchers to collect data that can be used to answer questions not only about visual attention, but also about a broad range of other perceptual, cognitive, and social skills and their development.

Effectiveness of adults' spontaneous exploration while perceiving affordances for squeezing through doorways.

When motor abilities change, people need to generate information to recalibrate their perception through active exploration. Most prior research has focused on observers' ability to update perception by executing experimenter-specified exploratory behaviors, however, the question of how observers spontaneously choose how to explore has been overlooked. We asked how effectively adults decide to explore when adapting to changes in their ability to squeeze through doorways. Results revealed that participants made efficient decisions about when to explore by approaching and practicing-they most often explored doorways that were near the limit of their abilities, and participants explored less often as their perceptual calibration improved. However, participants made sub-optimal decisions about how to explore, which resulted in a failure to fully recalibrate. We discuss the implications of these findings for understanding the processes of perceptual-motor recalibration that underlie real-world behavior.

Rate of recalibration to changing affordances for squeezing through doorways reveals the role of feedback.

Recalibration of affordance perception in response to changing motor abilities can only occur if observers detect appropriate perceptual information. Recent work suggests that although many affordances can be recalibrated without practicing the specific action to gather outcome feedback-information about whether the attempted action succeeded or failed-calibration of other affordances might depend on outcome feedback (Franchak, Attent Percept Psychophys 79:1816-1829, 2017). However, past work could not rule out the possibility that practicing the action produced perceptual-motor feedback besides outcome feedback that facilitated recalibration. The results of two experiments support the hypothesis that recalibration in a doorway squeezing task depends on outcome feedback as opposed to perceptual-motor feedback. After putting on a backpack that changed participants' doorway squeezing ability, affordance judgments were uncalibrated and remained so even after making repeated judgments. However, after practicing the action, which produced outcome feedback, judgments rapidly calibrated. Moreover, the order of feedback information directly impacted participants' judgments: Participants did not recalibrate if they received only success experience or only failure experience. Recalibration only occurred after participants received both types of feedback experiences, suggesting that outcome feedback is necessary for recalibration in the doorway squeezing task. More generally, the results of the current study support a key tenet of ecological psychology-that affordance perception depends on action-specific information about body-environment relations.

See and be seen: Infant-caregiver social looking during locomotor free play.

Face-to-face interaction between infants and their caregivers is a mainstay of developmental research. However, common laboratory paradigms for studying dyadic interaction oversimplify the act of looking at the partner's face by seating infants and caregivers face to face in stationary positions. In less constrained conditions when both partners are freely mobile, infants and caregivers must move their heads and bodies to look at each other. We hypothesized that face looking and mutual gaze for each member of the dyad would decrease with increased motor costs of looking. To test this hypothesis, 12-month-old crawling and walking infants and their parents wore head-mounted eye trackers to record eye movements of each member of the dyad during locomotor free play in a large toy-filled playroom. Findings revealed that increased motor costs decreased face looking and mutual gaze: Each partner looked less at the other's face when their own posture or the other's posture required more motor effort to gain visual access to the other's face. Caregivers mirrored infants' posture by spending more time down on the ground when infants were prone, perhaps to facilitate face looking. Infants looked more at toys than at their caregiver's face, but caregivers looked at their infant's face and at toys in equal amounts. Furthermore, infants looked less at toys and faces compared to studies that used stationary tasks, suggesting that the attentional demands differ in an unconstrained locomotor task. Taken together, findings indicate that ever-changing motor constraints affect real-life social looking.

Exploratory behaviors and recalibration: What processes are shared between functionally similar affordances?

Recalibration of affordance perception allows observers to adapt to changes in the body's size or abilities that alter possibilities for action. Of key interest is understanding how exploratory behaviors lead to successful recalibration. The present study was designed to test a novel hypothesis-that the same processes of exploration and recalibration should generalize between affordances that share a similar function. Most affordances for fitting the body through openings are recalibrated without feedback from practicing the action; locomotion exploration is sufficient. The present study used a different fitting task, squeezing through doorways, to determine whether locomotor experience was sufficient for recalibrating to changes in body size that altered affordances. Participants were unable to recalibrate from locomotor experience, demonstrating that exploratory behaviors do not necessarily generalize between functionally similar affordances. Participants only recalibrated following action practice or after receiving feedback about judgment accuracy, suggesting that the informational requirements of the squeezing task may differ from those of other fitting tasks. Implications for affordance theory are discussed.