Young infants' visual fixation patterns in addition and subtraction tasks support an object tracking account.

Investigating infants' numerical ability is crucial to identifying the developmental origins of numeracy. Wynn (1992) claimed that 5-month-old infants understand addition and subtraction as indicated by longer looking at outcomes that violate numerical operations (i.e.

Limits of Object Persistence: Young Infants Perceive Continuity of Vertical and Horizontal Trajectories, But Not 45-Degree Oblique Trajectories.

Previous research indicated that 4-month-old infants perceive continuity of objects moving on horizontal trajectories but appear to have difficulty processing occlusion events involving oblique trajectories. However, because perception of continuity of vertical trajectories has not been tested, it is uncertain whether this indicates a specific deficit for oblique trajectories or a specific advantage for horizontal trajectories. We evaluated the contribution of trajectory orientation and the form of occlusion in three experiments with one hundred and forty-four 4-month-olds.

Perception of occlusion by young infants: Must the occlusion event be congruent with the occluder?

Four-month-old infants perceive continuity of an object's trajectory through occlusion, even when the occluder is illusory, and several cues are apparently needed for young infants to perceive a veridical occlusion event. In this paper we investigated the effects of dislocating the spatial relation between the occlusion events and the visible edges of the occluder. In two experiments testing 60 participants, we demonstrated that 4-month-olds do not perceive continuity of an object's trajectory across an occlusion if the deletion and accretion events are spatially displaced relative to the occluder edges (Experiment 1) or if deletion and accretion occur along a linear boundary that is incorrectly oriented relative to the occluder's edges (Experiment 2).

Trajectory perception and object continuity: effects of shape and color change on 4-month-olds' perception of object identity.

Previous work has demonstrated that infants use object trajectory continuity as a cue to the constant identity of an object, but results are equivocal regarding the role of object features, with some work suggesting that a change in the appearance of an object does not cue a change in identity. In an experiment involving 72 participants, we investigated the effects of changing object shape and color, singly and in combination, on 4-month-olds' perception of object continuity. A change in the shape of an object while it passed behind an occluder had no effect on perception of continuity, whereas a change in shape and color led to perception of discontinuity, and a change in color led to no clear percept regarding continuity or discontinuity.

The effects of auditory information on 4-month-old infants' perception of trajectory continuity.

Young infants perceive an object's trajectory as continuous across occlusion provided the temporal or spatial gap in perception is small. In 3 experiments involving 72 participants the authors investigated the effects of different forms of auditory information on 4-month-olds' perception of trajectory continuity. Provision of dynamic auditory information about the object's trajectory enhanced perception of trajectory continuity.

Illusory contour figures are perceived as occluding contours by 4-month-old infants.

Although 4-month-olds perceive continuity of an object's trajectory through occlusion, little is known about the information specifying an occluding surface at this age. We investigated this in 3 experiments involving 84 participants. Testing the claim that 5-month-olds are unable to perceive the Kanizsa figure as an occluding surface (Csibra, 2001), we demonstrated that 4-month-olds perceived trajectory continuity behind this figure providing its horizontal extent was small.

Two- to eight-month-old infants' perception of dynamic auditory-visual spatial colocation.

From birth, infants detect associations between the locations of static visual objects and sounds they emit, but there is limited evidence regarding their sensitivity to the dynamic equivalent when a sound-emitting object moves. In 4 experiments involving thirty-six 2-month-olds, forty-eight 5-month-olds, and forty-eight 8-month-olds, we investigated infants' ability to process this form of spatial colocation. Whereas there was no evidence of spontaneous sensitivity, all age groups detected a dynamic colocation during habituation and looked longer at test trials in which sound and sight were dislocated.

Young infants' perception of unity and form in occlusion displays.

Young infants have been reported to perceive the unity of a center-occluded object when the visible ends of the object are aligned and undergo common motion but not when the edges of the object are misaligned (Johnson & Aslin, 1996). Using a recognition-based paradigm, the authors investigated the possibility that past research failed to provide sufficiently sensitive assessments of infants' perception of the unity of misaligned edges in partial occlusion displays. Positive evidence was obtained in 4-month-olds for veridical perception of the motion and location of a hidden region but not its orientation, whereas 7-month-olds, in contrast to the younger infants, appeared to respond to the orientation of the hidden region.