How do infants learn to perceive the backs of objects that they see only from a limited viewpoint? Infants' 3D object completion abilities emerge in conjunction with developing motor skillsindependent sitting and visual-manual exploration. Twenty-eight 4.5-to 7.5-month-old infants 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 to 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.Keywords perceptual development; 3D object perception; exploration; object manipulation; sitting Developmental psychology has a long history of linking achievements in infants' motor skills with improvements in perceptual and cognitive abilities. Piaget (1954), for example, proposed that infants' developing motor actions and subsequent exploration of the world are critical for learning and development. Likewise, E. J. Gibson (1988) argued that infants learn about the properties of the world through exploration and that developing motor skills constrain and guide how infants pick up information about objects, surfaces, and events. Piaget viewed motor skill acquisition as a launching point for perceptual and cognitive skills. In contrast, Gibson took seriously the proposition that motor action, perception, and cognition are linked in real time and throughout development: Perception and cognition remain inextricably grounded in the body and its actions (e.g., E. J. Gibson & Pick, 2000;Thelen & Smith, 1994). The current work was motivated by a developmental systems approach, which emphasizes the developmental processes that facilitate acquisition of new skills, even when the developmental history grows from non-obvious causal factors (e.g., Gottlieb, 2007; Spencer et al., in press). The present study examined how developmental changes in motor skills-sitting and manual exploration-affect three-dimensional (3D) object completion, that is, perceiving an object as a complete volume in visual space despite only seeing it from a limited viewpoint (Soska & Johnson, 2008).Correspondence should be addressed to: Kasey C. Soska, Department of Psychology, New York University, 6 Washington Place, Rm. 458, New York, NY 10003, Tel: (212) Object Exploration Facilitates Object PerceptionManual exploration provides information about objects in the environment-object properties, such as weight, shape, and surface texture, and affordances for action, such as grasping, banging, sliding, and rolling (Lockman, 2000). Different exploratory pr...

Despite hundreds of studies describing infants’ visual exploration of experimental stimuli, researchers know little about where infants look during everyday interactions. The current study describes the first method for studying visual behavior during natural interactions in mobile infants. Six 14-month-old infants wore a head-mounted eye-tracker that recorded gaze during free play with mothers. Results revealed that infants’ visual exploration is opportunistic and depends on the availability of information and the constraints of infants’ own bodies. Looks to mothers’ faces were rare following infant-directed utterances, but more likely if mothers were sitting at infants’ eye level. Gaze toward the destination of infants’ hand movements was common during manual actions and crawling, but looks toward obstacles during leg movements were less frequent.

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.

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°, providing only a limited view. Two displays, rotating 360°, 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.Piaget (1954) pioneered the study of infants' perceptual and cognitive abilities with his foundational work on object knowledge and spatial cognition. Since these original studies, a wealth of information on visual-cognitive abilities has accrued in such areas as object

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 inter-correlated, 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.