Adults conceptualize the world in terms of enduring physical objects...

The agent-based approach emphasizes the importance of learning through organism-environment interaction. This approach is part of a recent trend in computational models of learning and development toward studying autonomous organisms that are embedded in virtual or real environments. In this paper we introduce the concepts of online and offline sampling and highlight the role of online sampling in agent-based models. After comparing the strengths of each approach for modeling particular developmental phenomena and research questions, we describe a recent agent-based model of infant causal perception. We conclude by discussing some of the present limitations of agent-based models and suggesting how these challenges may be addressed. © 2001 Academic Press Computational models of learning and development are playing an increasingly critical role in child development research (Cassidy, 1990;

When an object moves behind an occluder and re-emerges, 4-month-old infants perceive trajectory continuity only when the occluder is narrow, raising the question of whether time or distance out of sight is the important constraining variable. One hundred and forty 4-month-olds were tested in five experiments aimed to disambiguate time and distance out of sight. Manipulating the object’s visible speed had no effect on infants ’ responses, but reducing occlusion time by increasing object speed while occluded induced perception of trajectory continuity. In contrast, slowing the ball while it was behind a narrow or intermediate screen did not modify performance. It is concluded that 4-month-olds perceive trajectory continuity when time or distance out of sight is short. In everyday environments, the objects that we encounter frequently pass into and out of sight as our view of them is obstructed by nearer objects, and yet we perceive these objects as enduring entities. Additionally, when objects move, we perceive their trajectories as continuous even though they may be invisible for part of their path of movement. This ability to fill in the gaps in perception is a fundamental aspect of object perception, and important questions arise regarding its developmental origins. Early work investigating young infants ’ perception of events in which an object passes behind a screen was framed in terms of infants ’ knowledge of object permanence. For instance, Bower, Broughton, and Moore (1971) reported that 2-month-olds anticipated the re-emergence of an object from behind a screen, evidence for object permanence. Moreover, they showed tracking disruption (i.e., oculomotor search) when an object emerged from behind a screen too soon, but not when it changed its form behind the screen, and Bower et al. (1971) interpreted this as indicating a difficulty in integrating object

Conditions for Young Infants ’ Failure 2 When viewing an event in which an object moves behind an occluder on part of its trajectory, 4-month-old infants perceive the trajectory as continuous only when time or distance out of sight is short. Little is known, however, about the conditions under which young infants perceive trajectories to be discontinuous. In the present studies we focus firstly on infants’ perception of trajectories that change during a period of occlusion. Four-month-olds perceive discontinuity in trajectories that change in height or orientation while behind an occluder, and this is true even when a change in direction could be due to an invisible bouncing collision with a surface. Further experiments reveal that infants do not perceive diagonal linear trajectories as continuous across an occlusion unless the occluding and revealing edges are orthogonal to the path of movement. Implications for theories of perceptual and cognitive development are discussed. Key words: infant; perception; trajectory; continuity