Evidence from adult psychophysics, brain imaging, and honeybee's behaviour has been reported to support the notion that topological properties are the primitives of visual representation (Chen, 1982 Science 218 699-700). Here, we ask how the sensitivity to topological property might originate during development. Specifically, we tested 1.5- to 6-month-old infants' visual sensitivity for topological versus geometric properties with the forced-choice novelty preference technique. A disk and a ring were used in the topologically different condition (experiment 1), while a disk and a triangle were used in the geometrically different condition (experiment 2). Spontaneous preferences for the disk, the ring, and the triangle were measured pairwise using the preferential looking-time technique (experiment 3). The results showed that infants could reliably discriminate stimuli based on topological differences, but failed to do so with geometric differences. Moreover, in the generalisation task, infants showed higher novelty preference for the topologically different figure (the ring). In addition, the results of both experiments cannot be attributed to a spontaneous preference for the ring or for the disk. Further analysis on individual infants' age and performance revealed two distinct developmental trends. Infants seem to be sensitive to topological differences as young as 1.5 months, while their ability to discriminate geometric differences was at chance before 3 months and gradually improved with age. Taken together, our findings suggested an early sensitivity for topological property, at least for the detection of stimuli with or without a hole.

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Primitive, and invariant across degraded visual settings, topological properties may serve as the basis for object recognition in an ever-changing world. The present study investigated whether human neonates exhibit an intrinsic visual sensitivity for a frequently encountered topological property, the presence or absence of a hole in a 2D shape. Using the familiarization/visual-paired comparison procedures with looking time measurement, we tested forty-three 0 to 4 day-old neonates' visual discriminability. The infants were randomly assigned to one of the three conditions: Condition 1: a disk vs. a ring (topologically different, geometrically similar), Condition 2: a disk vs. a triangle (topologically equivalent, geometrically different), or Condition 3: a ring vs. an S-like figure (topologically different, and total area equated). Based on infant's novelty preference scores derived by their looking time, the results showed that neonates were able to differentiate the shapes in Conditions 1 and 3, but not in Condition 2, suggesting a sensitivity for topological but not geometrical property. In sum, the present finding supports the notion that the ability to perceive visual topological information may be readily present at birth, at least for the presence or absence of a hole in a 2D shape.

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