Kasey C. Soska

Development of Three-Dimensional Object Completion in Infancy.

Three-dimensional (3D) object completion was investigated by habituating 4- and 6-month-old infants (n= 24 total) with a computer-generated wedge stimulus that pivoted 15 degrees , providing only a limited view. Two displays, rotating 360 degrees , were then shown: a complete, solid volume and an incomplete, hollow form composed only of the sides seen during habituation. There were no reliable preferences for either test display by 4-month-olds. At 6 months, infants showed a reliable novelty preference for the incomplete test display. Infants in a control group (n= 24) not habituated to the limited-view wedge preferred neither test display. By 6 months, infants may represent simple objects as complete in 3D space despite a limited perspective. Possible mechanisms of development of 3D object completion are discussed.

On the other hand: Overflow movements of infants' hands and legs during unimanual object exploration

Motor overflow is extraneous movement in a limb not involved in a motor action. Typically, overflow is observed in people with neurological impairments and in healthy children and adults during strenuous and attention-demanding tasks. In the current study, we found that young infants produce vast amounts of motor overflow, corroborating claims of symmetry being the default state of the motor system. While manipulating an object with one hand, all 27 of the typically developing 4.5- to 7.5-month-old infants who we observed displayed overflow movements of the free hand (on 4/5 of unimanual actions). Mirror-image movements of the hands occurred on 1/8 of unimanual actions, and the hands and legs moved in synchrony on 1/3 of unimanual acts. Motor overflow was less frequent when infants were in a sitting posture and when infants watched their acting hand, suggesting that upright posture and visual examination may help to alleviate overflow and break obligatory symmetry in healthy infants.

Dynamic reaching in infants during binocular and monocular viewing

This study examined reaching in 6-, 8-, and 10-month-olds during binocular and monocular viewing in a dynamic reaching situation. Infants were rotated toward a flat vertical board and reached for objects at one of seven positions along a horizontal line at shoulder height. Hand selection, time to contact the object, and reaching accuracy were examined in both viewing conditions. Hand selection was strongly dependent on object location, not on infants’ age or whether one eye was covered. Monocular viewing and age did, however, affect time to object contact and contact errors: Infants showed longer contact times when one eye was covered, and 6-month-olds made more contact errors in the monocular condition. For right-hand selection, contact times were longer when the covered right eye was leading during the chair rotation. For left-hand selection, there were no differences in contact time due to whether the covered eye was leading during rotation.

Behavioral flexibility in learning to sit

What do infants learn when they learn to sit upright? We tested behavioral flexibility in learning to sit-the ability to adapt posture to changes in the environment-in 6- to 9-month-old infants sitting on forward and backward slopes. Infants began with slant at 0°; then slant increased in 2° increments until infants lost balance. Infants kept balance on impressively steep slopes, especially in the forward direction, despite the unexpected movements of the apparatus. Between slant adjustments while the slope was stationary, infants adapted posture to the direction and degree of slant by leaning backward on forward slopes and forward on backward slopes. Postural adaptations were nearly optimal for backward slopes. Sitting experience predicted greater postural adaptations and increased ability to keep balance on steeper changes of slant, but only for forward slopes. We suggest that behavioral flexibility is integral to learning to sit and increases with sitting experience.

The Multisensory Attention Assessment Protocol (MAAP): Characterizing individual differences in multisensory attention skills in infants and children and relations with language and cognition.

Multisensory attention skills provide a crucial foundation for early cognitive, social, and language development, yet there are no fine-grained, individual difference measures of these skills appropriate for preverbal children. The Multisensory Attention Assessment Protocol (MAAP) fills this need. In a single video-based protocol requiring no language skills, the MAAP assesses individual differences in three fundamental building blocks of attention to multisensory events—the duration of attention maintenance, the accuracy of intersensory (audiovisual) matching, and the speed of shifting—for both social and nonsocial events, in the context of high and low competing visual stimulation. In Experiment 1, 2- to 5-year-old children (N = 36) received the MAAP and assessments of language and cognitive functioning. In Experiment 2 the procedure was streamlined and presented to 12-month-olds (N = 48). Both infants and children showed high levels of attention maintenance to social and nonsocial events, impaired attention maintenance and speed of shifting when competing stimulation was high, and significant intersensory matching. Children showed longer maintenance, faster shifting, and less impairment from competing stimulation than infants. In 2- to 5-year-old children, duration and accuracy were intercorrelated, showed increases with age, and predicted cognitive and language functioning. The MAAP opens the door to assessing developmental pathways between early attention patterns to audiovisual events and language, cognitive, and social development.

Assessing individual differences in the speed and accuracy of intersensory processing in young children: The intersensory processing efficiency protocol.

Detecting intersensory redundancy guides cognitive, social, and language development. Yet, researchers lack fine-grained, individual difference measures needed for studying how early intersensory skills lead to later outcomes. The intersensory processing efficiency protocol (IPEP) addresses this need. Across a number of brief trials, participants must find a sound-synchronized visual target event (social, nonsocial) amid five visual distractor events, simulating the “noisiness” of natural environments. Sixty-four 3- to 5-year-old children were tested using remote eye-tracking. Children showed intersensory processing by attending to the sound-synchronous event more frequently and longer than in a silent visual control, and more frequently than expected by chance. The IPEP provides a fine-grained, nonverbal method for characterizing individual differences in intersensory processing appropriate for infants and children.