Browsing by Author "Joh, Amy S"

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Open Access
Effects of priming duration on retention over the first 1 1/2 years of life.
(Dev Psychobiol, 2005-07) Hsu, Vivian C; Rovee-Collier, Carolyn; Hill, Debra L; Grodkiewicz, Jill; Joh, Amy S
Exposing individuals to an isolated component (a prime) of a prior event alleviates its forgetting. Two experiments with 120 human infants between 3 and 18 months of age determined the minimum duration of a prime that can reactivate a forgotten memory and how long the reactivated memory persists. Infants learned an operant task, forgot it, were exposed to the prime, and later were tested for renewed retention. In Experiment 1, the minimum duration of an effective prime decreased logarithmically with age, but was always longer than the duration of a mere glance. In Experiment 2, the reactivated memory was forgotten twice as fast after a minimum-duration prime as after a full-length one, irrespective of priming delay and infant age. These data reveal that the minimum effective prime duration psychophysically equates the accessibility of forgotten memories. We conclude that priming is perceptually based with effects that are organized on a ratio (log) scale.
Open Access
Gauging possibilities for action based on friction underfoot.
(J Exp Psychol Hum Percept Perform, 2007-10) Joh, Amy S; Adolph, Karen E; Narayanan, Priya J; Dietz, Victoria A
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.
Open Access
Learning from falling.
(Child Dev, 2006-01) Joh, Amy S; Adolph, Karen E
Walkers fall frequently, especially during infancy. Children (15-, 21-, 27-, 33-, and 39-month-olds) and adults were tested in a novel foam pit paradigm to examine age-related changes in the relationship between falling and prospective control of locomotion. In trial 1, participants walked and fell into a deformable foam pit marked with distinct visual cues. Although children in all 5 age groups required multiple trials to learn to avoid falling, the number of children who showed adult-like, 1-trial learning increased with age. Exploration and alternative locomotor strategies increased dramatically on learning criterion trials and displays of negative affect were limited. Learning from falling is discussed in terms of the immediate and long-term effects of falling on prospective control of locomotion.
Open Access
Object-Directed Action Experiences and their Effect on Cognitive and Social Development
(2010) Libertus, Klaus
Reaching is an important and early emerging motor skill that allows infants to interact with the physical and social world (e.g., when sharing objects). Despite the importance of motor experiences in early infancy, few studies have considered the influence of reaching behavior on cognitive, social, and motor development. In this dissertation, reaching behavior was selectively manipulated in 73 non-reaching three-month-old infants using four different training interventions. Infants' reaching and social cognition skills were assessed and compared, and the long-term effects of one particular training intervention were explored.

Of the four training interventions used here, one procedure--referred to as active training--facilitated domain-specific development (reaching and grasping behavior) and increased infants' preferential orienting towards faces in a visual-preference task (face preference). None of the remaining three training interventions facilitated motor development and only one increased face-preference behavior. However, a relation between face-preference behavior and motor experience was present in all trained infants as well as in three- to 11-month-old untrained infants. In untrained infants, face-preference behavior was the earliest social-cognition skill to emerge and was related to later emerging skills such as gaze following. Therefore, a preference for faces may be an important basic social-cognition skill that influences future social development.

Additionally, the long-term effects of the active-training procedure were assessed in 14 infants who were tested one year after they had participated in the active-training intervention. Even after one year, converging evidence showed advanced manual exploration and object-engagement skills in trained compared to untrained infants.

The studies described in this dissertation attempt to systematically investigate the role of early reaching experiences on subsequent development of motor and social cognition behaviors. The present findings demonstrate the importance of self-produced motor experiences on the development of social cognition and have implications for our understanding of typical development and the etiology of developmental disorders in social cognition.
Open Access
Why walkers slip: shine is not a reliable cue for slippery ground.
(Percept Psychophys, 2006-04) Joh, Amy S; Adolph, Karen E; Campbell, Margot R; Eppler, Marion A
In a series of four studies, we investigated the visual cues that walkers use to predict slippery ground surfaces and tested whether visual information is reliable for specifying low-friction conditions. In Study 1, 91% of participants surveyed responded that they would use shine to identify upcoming slippery ground. Studies 2-4 confirmed participants' reliance on shine to predict slip. Participants viewed ground surfaces varying in gloss, paint color, and viewing distance under indoor and outdoor lighting conditions. Shine and slip ratings and functional walking judgments were related to surface gloss level and to surface coefficient of friction (COF). However, judgments were strongly affected by surface color, viewing distance, and lighting conditions--extraneous factors that do not change the surface COF. Results suggest that, although walkers rely on shine to predict slippery ground, shine is not a reliable visual cue for friction. Poor visual information for friction may underlie the high prevalence of friction-related slips and falls.