Faculty Bibliography

Perceiving possibilities for action-affordances-requires sensitivity, accuracy, and consistency. In the current study, we tested children of different ages (16-month-olds to 7-year-olds) and adults to examine the development of affordance perception for reaching through openings of various sizes. Using a psychophysical procedure, we estimated individual affordance functions to characterize participants' actual ability to fit their hand through openings and individual decision functions to characterize attempts to reach. Decisions were less accurate in younger children (16-month-olds to 5-year-olds); they were more likely to attempt impossible openings and to touch openings prior to refusing, suggesting a slow developmental trend in learning to perceive affordances for fitting through openings. However, analyses of multiple outcome measures revealed that the youngest participants were equally consistent in their decision making as the oldest ones and that every age group showed sensitivity to changes in the environment by scaling their attempts to opening size.

How children pick up a tool reveals their ability to plan an action with the end goal in mind. When presented with a spoon whose handle points away from their dominant hand, children between infancy and 8 years of age progress from using an awkward ulnar grip that causes food to spill from the spoon to consistently using a radial grip. At 4 years of age children's grip strategies are highly variable, including the awkward grips of infancy and use of the non-dominant hand, but they also employ adult-like grips never seen in infancy. By 8 years of age the infantile ulnar grip has completely disappeared and is replaced by more mature and effective grips that indicates better planning for the end goal.

The transition from crawling to walking requires infants to relinquish their status as experienced, highly skilled crawlers in favor of being inexperienced, lowskilled walkers. Yet infants willingly undergo this developmental transition, despite incurring costs of shaky steps, frequent falls, and inability to gauge affordances for action in their new upright posture. Why do infants persist with walking when crawling serves the purpose of independent mobility? In this article, we present an integrative analysis of the costs and benefits associated with crawling and walking that challenges prior assumptions, and reveals deficits of crawling and benefits of upright locomotion that were previously overlooked. Inquiry into multiple domains of development reveals that the benefits of persisting with walking outweigh the costs: Compared to crawlers, walking infants cover more space more quickly, experience richer visual input, access and play more with distant objects, and interact in qualitatively new ways with caregivers.

We propose a new way to describe affordances for action. Previous characterizations of affordances treat action possibilities as binary categories-either possible or impossible-separated by a critical point. Here, we show that affordances are probabilistic functions, thus accounting for variability in motor performance. By measuring an affordance function, researchers can describe the likelihood of success for every unit of the environment. We demonstrate how to fit an affordance function to performance data using established psychophysical procedures and illustrate how the threshold and variability parameters describe different possibilities for action. Finally, we discuss the implications of probabilistic affordances for development, perception, and decision-making.

"Cruising" infants can only walk using external support to augment their balance. We examined cruisers' understanding of support for upright locomotion under four conditions: cruising over a wooden handrail at chest height, a large gap in the handrail, a wobbly unstable handrail, and an ill positioned low handrail. Infants distinguished among the support properties of the handrails with differential attempts to cruise and handrail-specific forms of haptic exploration and gait modifications. They consistently attempted the wood handrail, rarely attempted the gap, and occasionally attempted the low and wobbly handrails. On the wood and gap handrails, attempt rates matched the probability of cruising successfully; but on the low and wobbly handrails, attempt rates under- and over-estimated the probability of success, respectively. Haptic exploration was most frequent and varied on the wobbly handrail, and gait modifications-including previously undocumented "knee cruising"-were most frequent and effective on the low handrail. Results are discussed in terms of developmental changes in the meaning of support.

Possibilities for action depend on the fit between the body and the environment. Perceiving what actions are possible is challenging, because the body and the environment are always changing. How do people adapt to changes in body size and compression? In Experiment 1, we tested pregnant women monthly over the course of pregnancy to determine whether they adapted to changing possibilities for squeezing through doorways. As women gained belly girth and weight, previously passable doorways were no longer passable, but women's decisions to attempt passage tracked their changing abilities. Moreover, their accuracy was equivalent to that of nonpregnant adults. In Experiment 2, nonpregnant adults wore a "pregnancy pack" that instantly increased the size of their bellies, and they judged whether doorways were passable. Accuracy in the "pregnant" participants was only marginally worse than that of actual pregnant women, suggesting that participants adapted to the prosthesis during the test session. In Experiment 3, participants wore the pregnancy pack and gauged passability before and after attempting passage. The judgments were grossly inaccurate prior to receiving feedback. These findings indicate that experience facilitates perceptual-motor recalibration for certain types of actions.

Recent research has revealed the important role of multimodal object exploration in infants' cognitive and social development. Yet, the real time effects of postural position on infants' object exploration have been largely ignored. In the current study, 5- to 7-month-old infants (N = 29) handled objects while placed in supported sitting, supine, and prone postures, and their spontaneous exploratory behaviors were observed. Infants produced more manual, oral, and visual exploration in sitting compared to lying supine and prone. Moreover, while sitting, infants more often coupled manual exploration with mouthing and visual examination. Infants' opportunities for learning from object exploration are embedded within a real time postural context that constrains the quantity and quality of exploratory behavior.

Based largely on the famous "visual cliff" paradigm, conventional wisdom is that crawling infants avoid crossing the brink of a dangerous drop-off because they are afraid of heights. However, recent research suggests that the conventional wisdom is wrong. Avoidance and fear are conflated, and there is no compelling evidence to support fear of heights in human infants. Infants avoid crawling or walking over an impossibly high drop-off because they perceive affordances for locomotion-the relations between their own bodies and skills and the relevant properties of the environment that make an action such as descent possible or impossible.

Mental health services embedded within school systems can create a continuum of integrative care that improves both mental health and educational attainment for children. To strengthen this continuum, and for optimum child development, a reconfiguration of education and mental health systems to aid implementation of evidence-based practice might be needed. Integrative strategies that combine classroom-level and student-level interventions have much potential. A robust research agenda is needed that focuses on system-level implementation and maintenance of interventions over time. Both ethical and scientific justifications exist for integration of mental health and education: integration democratises access to services and, if coupled with use of evidence-based practices, can promote the healthy development of children.

This study examined proximal risk and protective factors that contribute to academic achievement among 130 Latino students. Participating students were 56.2% female and 35.3% foreign-born (mean age = 11.38, SD = .59). Acculturative stress, immigrant status, child gender, parental monitoring, traditional cultural values, mainstream values, and English language proficiency were explored in relation to academic achievement. Higher levels of parental monitoring, English language proficiency, and female gender were associated with higher grades, while mainstream values were associated with lower grades. In addition, a significant interaction between acculturative stress and immigrant status was found, such that higher acculturative stress was related to poorer grades for U.S.-born students in particular. Thus, parental monitoring and female gender are potential protective factors, while identification with mainstream values and low English language proficiency are risk factors for poor grades. U.S.-born students may be particularly vulnerable to the effects of acculturative stress.