Kaldy, Z. (in press). Slow developmental processes of the visual system: Do preschoolers succumb to the Ebbinghaus illusion? In: Pleh, C. & Gervain, J. (Eds.) Cognitive science. Osiris, Budapest. (In Hungarian)

Some recent studies have shown that certain aspects of perceptual organization develop rather slowly in humans. The development of contour integration (Kovács, Kozma, Fehér & Benedek, 1999) and vernier acuity (Skoczenski & Aslin, 1995) protracts well into late childhood. In order to study the development of a high-level perceptual organizational capacity, context integration, we compared the magnitude of a size contrast illusion (Ebbinghaus illusion) in children and adults using a two-alternative forced choice method. The magnitude of the illusion effect was significantly smaller in children than in adults. Closer to veridical size estimations by children demonstrate that the perception of the local target is less affected by stimulus context in their case. Our interpretation is that context integration is not fully developed in 4-year-olds. According to this hypothesis, immature cortical connectivity in extrastriate areas accounts for the reduced contextual sensitivity in children.