The development of luminance- and texture-defined form perception during the school-aged years

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 where C-optotypes were defined by either luminance or texture information, the latter necessitating extra-striate neural processing to be perceived. Typically developing children were placed in one of 4 school-age groups (6, 8, 10 and 12-year olds); an adult group was also assessed. The contrast threshold for the correct identification of gap-opening-orientation for C-optotypes defined by either texture- or luminance-contrast was measured. All participants were presented with C-optotypes with gap-openings presented in one 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 ages. As expected, gap-opening identification sensitivity (1/threshold) increased with age for all conditions. For both luminance-defined conditions, adult-like performance was manifested by 12 years of age. By comparison, at 12 years of age, the sensitivity to texture-defined C-optotypes was significantly lower than that of adults, having increased steadily from the age of 6 years. These results suggest that mechanisms underlying static form perception mature at different ages 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.