Abstract
The functional distinction between vision for perception and vision for action is well documented in the mature visual system. Ganel and colleagues recently provided direct evidence for this dissociation showing that while visual processing for perception follows Weber’s fundamental law of psychophysics, action violates this law. We tracked the developmental trajectory of this functional dissociation, asking (a) whether the qualitatively different pattern observed in adults of adherence of perception but not of action to Weber's law would also be evident during early childhood, and (b) how early in life the adherence of perception to this fundamental law of psychophysics becomes adult-like. Children aged 5-8 and adults were asked to either estimate the size of discs (perception), or grasp discs (action) varying in diameter. Interestingly, variability of perceptual estimates increased as a function of object size in accord with Weber’s law, while variability of grasping did not scale with object size, at all ages tested. The results also revealed, however, developmental changes in the adherence of perception to Weber’s law: while adults demonstrated a linear increment in JNDs with object size, the changes in JNDs for both the 5- to 6- and 7- to 8-year-olds were best described by a quadratic fit. Adult-like pattern of linear increment in JNDs as a function of object size was observed only after the age of 10.These results provide the first clear evidence for an early emergence of the dissociation between perception and action. However, developmental changes in visual sensitivity to changes in object size suggest the refinement of the perceptual system in its sensitivity to relative metrics of the visual world during childhood.
Meeting abstract presented at VSS 2012