Abstract
The objective of the present study was to assess the development of luminance- and texture-defined static form perception in school-aged children. This was done using an adapted Landolt C technique (Bertone & Faubert, submitted) where C-optotypes are defined by either luminance- or texture-contrast, the latter necessitating non-linear processing beyond standard striate-mediated analysis to be resolved. Typically-developing children were placed in one of 4 school-age groups ranging from 5 to 12 years of age; an adult group (18 years+) was also assessed. Gap-opening-identification thresholds for C-optotypes defined by either luminance-contrast (with and without noise) or texture-contrast (noise) were measured. All participants were presented with C-optotypes with gap-openings presented in either of 4 orientations (up, down, left or right). An adaptive staircase procedure was used to measure gap-opening-identification thresholds (minimum luminance- or texture-contrast modulation) for all three conditions and age groups. In addition, the developmental level of each participant, as defined by verbal mental ability, was assessed using the Peabody Picture Vocabulary Test (PPVT). As expected, gap-opening identification sensitivity (1/threshold) increased with age for all conditions. For both luminance-defined (with and without noise) conditions, adult-like performance was attained between the ages of 9 and 12 years. By comparison, the sensitivity to texture-defined C-optotypes was significantly lower than that of adults at 12 years of age, having increased steadily from the age of 5 years. These results suggest that mechanisms underlying static form perception develop at different rates, depending on the physical attribute defining the form. Luminance-defined form perception appears to reach adult-like levels (or plateau) earlier than for texture-defined information, suggesting that the development of mechanisms mediating higher-order form perception persist into adolescence.
Funded by CIHR-Clinical Research Initiative Fellowship (AB), FRSQ Doctoral Scholarship (JH) & Canada Research Chair to (KC).