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What infants decide to do does not necessarily reflect the extent of what they know. In the current study, 17-month-olds were encouraged to walk through openings of varying width under risk of entrapment. Infants erred by squeezing into openings that were too small and became stuck, suggesting that they did not accurately perceive whether they could fit. However, a second penalty condition revealed accurate action selection when errors resulted in falling, indicating that infants are indeed perceptually sensitive to fitting through openings. Furthermore, independent measures of perception were equivalent between the two penalty conditions, suggesting that differences in action selection resulted from different penalties, not lack of perceptual sensitivity. [ABSTRACT FROM AUTHOR]

Carrying objects requires coordination of manual action and locomotion. This study investigated spontaneous carrying in 24 walkers who were 13 months old and 26 crawlers who were 13 months old during 1-hr, naturalistic observations in the infants' homes. Carrying was more common in walkers, but crawlers also carried objects. Typically, walkers carried objects in their hands, whereas crawlers multitasked by using their hands simultaneously for holding objects and supporting their bodies. Locomotor experience predicted frequency of carrying in both groups, suggesting that experienced crawlers and walkers perceive their increased abilities to handle objects while in motion. Despite additional biomechanical constraints imposed by holding an object, carrying may actually improve upright balance: Crawlers rarely fell while carrying an object, and walkers were more likely to fall without an object in hand than while carrying. Thus, without incurring an additional risk of falling, spontaneous carrying may provide infants with new avenues for combining locomotor and manual skills and for interacting with their environments. [ABSTRACT FROM AUTHOR]

Three experiments investigated whether 14- and 15-month-old infants use information for both friction and slant for prospective control of locomotion down slopes. In Experiment 1, high- and low-friction conditions were interleaved on a range of shallow and steep slopes. In Experiment 2, friction conditions were blocked. In Experiment 3, the low-friction surface was visually distinct from the surrounding high-friction surface. In all three experiments, infants could walk down steeper slopes in the high-friction condition than they could in the low-friction condition. Infants detected affordances for walking down slopes in the high-friction condition, but in the low-friction condition, they attempted impossibly slippery slopes and fell repeatedly. In both friction conditions, when infants paused to explore slopes, they were less likely to attempt slopes beyond their ability. Exploration was elicited by visual information for slant (Experiments 1 and 2) or by a visually distinct surface that marked the change in friction (Experiment 3). [ABSTRACT FROM AUTHOR]

How do infants learn to perceive the backs of objects that they see only from a limited viewpoint? Infants' 3-dimensional object completion abilities emerge in conjunction with developing motor skills - independent sitting and visual-manual exploration. Infants at 4.5 to 7.5 months of age (n = 28) were habituated to a limited-view object and tested with volumetrically complete and incomplete (hollow) versions of the same object. Parents reported infants' sitting experience, and infants' visual-manual exploration of objects was observed in a structured play session. Infants' self-sitting experience and visual-manual exploratory skills predicted looking at the novel, incomplete object on the habituation task. Further analyses revealed that self-sitting facilitated infants' visual inspection of objects while they manipulated them. The results are framed within a developmental systems approach, wherein infants' sitting skill, multimodal object exploration, and object knowledge are linked in developmental time. [ABSTRACT FROM AUTHOR]

Affordances--possibilities for action--are constrained by the match between actors and their environments. For motor decisions to be adaptive, affordances must be detected accurately. Three experiments examined the correspondence between motor decisions and affordances as participants reached through apertures of varying size. A psychophysical procedure was used to estimate an affordance threshold for each participant (smallest aperture they could fit their hand through on 50% of trials), and motor decisions were assessed relative to affordance thresholds. Experiment 1 showed that participants scale motor decisions to hand size, and motor decisions and affordance thresholds are reliable over two blocked protocols. Experiment 2 examined the effects of habitual practice: Motor decisions were equally accurate when reaching with the more practiced dominant hand and less practiced nondominant hand. Experiment 3 showed that participants recalibrate motor decisions to take changing body dimensions into account: Motor decisions while wearing a hand-enlarging prosthesis were similar to motor decisions without the prosthesis when data were normalized to affordance thresholds. Across experiments, errors in decisions to reach through too-small apertures were likely due to low penalty for error. [ABSTRACT FROM AUTHOR]

The authors examined the effects of locomotor experience on infants' perceptual judgments in a potentially risky situation—descending steep and shallow slopes—while manipulating social incentives to determine where perceptual judgments are most malleable. Twelve-month-old experienced crawlers and novice walkers were tested on an adjustable sloping walkway as their mothers encouraged and discouraged descent. A psychophysical procedure was used to estimate infants' ability to crawl/walk down slopes, followed by test trials in which mothers encouraged and discouraged infants to crawl/walk down. Both locomotor experience and social incentives affected perceptual judgments. In the encourage condition, crawlers only attempted safe slopes within their abilities, but walkers repeatedly attempted impossibly risky slopes, replicating previous work. The discourage condition showed where judgments are most malleable. When mothers provided negative social incentives, crawlers occasionally avoided safe slopes, and walkers occasionally avoided the most extreme 50° increment, although they attempted to walk on more than half the trials. Findings indicate that both locomotor experience and social incentives play key roles in adaptive responding, but the benefits are specific to the posture that infants use for balance and locomotion. [ABSTRACT FROM AUTHOR]

Developmental trajectories provide the empirical foundation for theories about change processes during development However, the ability to distinguish among alternative trajectories depends on how frequently observations are sampled. This study used real behavioral data, with real patterns of variability, to examine the effects of sampling at different intervals on characterization of the underlying trajectory. Data were derived from a set of 32 infant motor skills indexed daily during the first 18 months. Larger sampling intervals (2-31 days) were simulated by systematically removing observations from the daily data and interpolating over the gaps. Infrequent sampling caused decreasing sensitivity to fluctuations in the daily data: Variable trajectories erroneously appeared as step functions, and estimates of onset ages were increasingly off target Sensitivity to variation decreased as an inverse power function of sampling interval, resulting in severe degradation of the trajectory with intervals longer than 7 days. These findings suggest that sampling rates typically used by developmental researchers may be inadequate to accurately depict patterns of variability and the shape of developmental change. Inadequate sampling regimes therefore may seriously compromise theories of development. [ABSTRACT FROM AUTHOR]

The social cognition and perception-action literatures are largely separate, both conceptually and empirically. However, both areas of research emphasize infants' emerging abilities to use available information—social and perceptual information, respectively—for making decisions about action. Borrowing methods from both research traditions, this study examined whether 18-month-old infants incorporate both social and perceptual information in their motor decisions. The infants' task was to determine whether to walk down slopes of varying risk levels as their mothers encouraged or discouraged walking. First, a psychophysical procedure was used to determine slopes that were safe, borderline, and risky for individual infants. Next, during a series of test trials, infants received mothers' advice about whether to walk. Infants used social information selectively: They ignored encouraging advice to walk down risky slopes and discouraging advice to avoid safe slopes, but they deferred to mothers' advice at borderline slopes. Findings indicate that 18-month-old infants correctly weigh competing sources of information when making decisions about motor action and that they rely on social information only when perceptual information is inadequate or uncertain. [ABSTRACT FROM AUTHOR]

Standing and walking generate information about friction underfoot. Five experiments examined whether walkers use such perceptual information for prospective control of locomotion. In particular, do walkers integrate information about friction underfoot with visual cues for sloping ground ahead to make adaptive locomotor decisions? Participants stood on low-, medium-, and high-friction surfaces on a flat platform and made perceptual judgments for possibilities for locomotion over upcoming slopes. Perceptual judgments did not match locomotor abilities: Participants tended to overestimate their abilities on low-friction slopes and underestimate on high-friction slopes (Experiments 1-4). Accuracy improved only for judgments made while participants were in direct contact with the slope (Experiment 5), highlighting the difficulty of incorporating information about friction underfoot into a plan for future actions. [ABSTRACT FROM AUTHOR]

In 2 experiments the authors demonstrated that adaptive locomotion can involve means-ends problem solving. Sixteen-month-old toddlers crossed bridges of varying widths in the presence or absence of a handrail. Babies attempted wider bridges more often than narrow ones, and attempts on narrow bridges depended on handrail presence. Toddlers had longer latencies, examined the bridge and handrail more closely, and modified their gait when bridges were narrow and/or the handrail was unavailable. Infants who explored the bridge and handrail before stepping onto the bridge and devised alternative bridgecrossing strategies were more likely to cross successfully. Results challenge traditional conceptualizations of tools: Babies used the handrail as a means for augmenting balance and for carrying out an otherwise impossible goal-directed task. [ABSTRACT FROM AUTHOR]

Examines the effects of changing body dimensions on infant locomotion. Reliability of a psychophysical procedure for testing the locomotor ability of children; Capability of infants to adapt to changes in their body dimensions; Process of infant adoption to changing body dimensions; Drawbacks of adaptive locomotion.

Examines how infants in early stages of walking determine whether a hill is safe or risky for locomotion. Perception of affordances for locomotion; Individual differences in ascent; Individual differences in descent; Walking boundaries on slopes; Function of exploratory activity.

Looks at Arnold Lucius Gesell's important and lasting impact on the field of developmental psychology. His developmental norms; Maturationism; Gesell's professional career; Louis Terman; Hall's questionnaire method for describing `the contents of children's minds'; Gesell's and Piaget's deep roots in the science of biology; Gessel's debt to Darwin; Embryologist G.E. Coghill; More.

Infants learn nouns during object-naming events--moments when caregivers name the object of infants' play (e.g., ball as infant holds a ball). Do caregivers also label the actions of infants' play (e.g., roll as infant rolls a ball)? We investigated connections between mothers' verb inputs and infants' actions. We video-recorded 32 infant-mother dyads for 2 hr at home (13 month olds, n = 16; 18 month olds, n = 16; girls, n = 16; White, n = 23; Asian, n = 2; Black, n = 1; other, n= 1; multiple races, n = 5; Hispanic/Latinx, n = 2). Dyads were predominantly from middle-class to upper middle-class households. We identified each manual verb (e.g., press, shake) and whole-body verb (e.g., kick, go) that mothers directed to infants. We coded whether infants displayed manual and/or whole-body actions during a 6-s window surrounding the verb (i.e., 3 s prior and 3 s after the named verb). Mothers' verbs and infant actions were largely congruent: Whole-body verbs co-occurred with whole-body actions, and manual verbs co-occurred with manual actions. Moreover, half of mothers' verbs corresponded precisely to infants' concurrent action (e.g., infant pressed button as mother said, "Press the button"). In most instances, mothers commented on rather than instigated infants' actions. Findings suggest that verb learning is embodied, such that infants' motor actions offer powerful cues to verb meanings. Furthermore, our approach highlights the value of cross-domain research integrating infants' developing motor and language skills to understand word learning. [ABSTRACT FROM AUTHOR]

Researchers routinely infer learning and other unobservable psychological functions based on observable behavior. But what behavioral changes constitute evidence of learning? The standard approach is to infer learning based on a single behavior across individuals, including assumptions about the direction and magnitude of change (e.g., everyone should avoid falling repeatedly on a treacherous obstacle). Herewe illustrate the benefits of an alternative "multiexpression, relativist, agnostic, individualized" approach. We assessed infant learning from falling based on multiple behaviors relative to each individual's baseline, agnostic about the direction and magnitude of behavioral change. We tested infants longitudinally (10.5-15 months of age) over the transition from crawling to walking. At each session, infants were repeatedly encouraged to crawl or walk over a fall-inducing foam pit interspersed with no-fall baseline trials on a rigid platform. Our approach revealed two learning profiles. Like adults in previous work, "pit-avoid" infants consistently avoided falling. In contrast, "pit-go" infants fell repeatedly across trials and sessions. However, individualized comparisons to baseline across multiple locomotor, exploratory, and social-emotional behaviors showed that pit-go infants also learned at every session. But they treated falling as an unimpactful "pratfall" rather than an aversive "pitfall." Pit-avoid infants displayed enhanced learning across sessions and partial transfer of learning from crawling to walking, whereas pit-go infants displayed neither. Thus, reliance on a predetermined, "one-size-fits-all" behavioral expression of a psychological function can obscure different behavioral profiles and lead to erroneous inferences. [ABSTRACT FROM AUTHOR]

The article presents an obituary for psychologist Esther Stillman Thelen who died of tongue cancer on December 29, 2004.

Behavioral flexibility--the ability to tailor motor actions to changing body-environment relations--is critical for functional movement. Navigating the everyday environment requires the ability to generate a wide repertoire of actions, select the appropriate action for the current situation, and implement it quickly and accurately. We used a new, adjustable barrier paradigm to assess flexibility of motor actions in 20 17-month-old (8 girls) and 14 13-month-old (7 girls) walking infants, and a comparative sample of 14 adults (8 women). Most participants were white, non-Hispanic, and middle class. Participants navigated under barriers normalized to their standing height (overhead, eye-, chest-, hip-, and knee-heights). Decreases in barrier height required lower postures for passage. Every participant altered their initial walking posture according to barrier height for every trial, and all but 2 13-month-olds found solutions for passage. Compared to infants, adults displayed a wider variety of strategies (squat-walking, half-kneeling, etc.), found more appropriate solutions based on barrier height (ducked at eye-height and low-crawled at knee-height), and implemented their solutions quickly (within 4 seconds) and accurately (without bumping their heads against the barrier). Infants frequently crawled even when the barrier height did not warrant a low posture, displayed multiple postural shifts prior to passage and thus took longer to go, and often bumped their heads. Infants' improvements were more related to age than to walking experience. Thus, development of flexibility likely involves the contributions of multiple domains--motor, perception, and cognition--that facilitate strategy selection and implementation. [ABSTRACT FROM AUTHOR]

How do young children learn to use everyday artifacts--doorknobs, zippers, and so on--in the ways they were designed to be used? Although the designed actions of such objects seem obvious to adults, little is known about how young children learn the "hidden affordances" of everyday objects. We encouraged 115 11- to 37-month-old children to open 2 types of containers: circular jars with twist-off lids (Experiment 1) and rectangular Tupperware-style containers with pull-off lids (Experiment 2). We varied container size to examine effects of the body-environment fit on display of the designed action and successful implementation of the designed action. Results showed a developmental progression from nondesigned actions to performance of the designed twisting or pulling actions to successful implementation of the designed action. Nondesigned actions decreased with age as performance of the designed action increased. Successful implementation lagged behind performance of the designed action. That is, even after children appeared to know what to do, they were still unsuccessful in opening the container. Why? For twist-offs, very large lids were difficult to manipulate, and younger children often twisted to the right, or in both directions, and did not persist in consecutive turns to the left. Larger pull-off containers required new strategies to stabilize the base, such as holding the container against the tabletop or the chest. Findings provide insights into the body-environment factors that facilitate children's learning and implementation of the hidden affordances inherent in everyday artifacts. [ABSTRACT FROM AUTHOR]

Some grips on the handle of a tool can be planned on the basis of information directly available in the scene. Other grips, however, must be planned on the basis of the final position of the hand. "End-state comfort" grips require an awkward or uncomfortable initial grip so as to later implement the action comfortably and efficiently. From a cognitive perspective, planning for end-state comfort requires a consistent representation of the entire action sequence, including the latter part, which is not based on information directly available in the scene. Many investigators have found that young children fail to demonstrate planning for end-state comfort and that adultlike performance does not appear until about 12 years of age. In 2 experiments, we used a hammering task that engaged children in a goal-directed action with multiple steps. We assessed end-state-comfort planning in novel ways by measuring children's hand choice, grip choice, and tool implementation over multiple trials. The hammering task also uniquely allowed us to assess the efficiency of implementation. We replicated the previous developmental trend in 4-, 8-, and 12-year-old children with our novel task. Most important, our data revealed that 4-year-olds are in a transitional stage during which several competing strategies were exhibited during a single session. Preschoolers changed their grip within trials and across trials, indicating awareness of errors and a willingness to sacrifice speed for more efficient implementation. The end-state-comfort grip initially competes as one grip type among many but gradually displaces all others. Children's sensitivity to costs and drive for efficiency may motivate this change. [ABSTRACT FROM AUTHOR]

This review challenges the traditional interpretation of infants' and young children's responses to three types of potentially "fear-inducing" stimuli-snakes and spiders, heights, and strangers. The traditional account is that these stimuli are the objects of infants' earliest developing fears. We present evidence against the traditional account, and provide an alternative explanation of infants' behaviors toward each stimulus. Specifically, we propose that behaviors typically interpreted as "fearful" really reflect an array of stimulus-specific responses that are highly dependent on context, learning, and the perceptual features of the stimuli. We speculate about why researchers so commonly misinterpret these behaviors, and conclude with future directions for studying the development of fear in infants and young children. (PsycINFO Database Record (c) 2019 APA, all rights reserved).