Neural sensitivity to natural image statistics changes during middle childhood.

Natural images have properties that adults' behavioral and neural responses are sensitive to, but the development of this sensitivity is not clear. Behaviorally, children acquire adult-like sensitivity to natural image statistics during middle childhood (Ellemberg et al., 2012), but infants exhibit sensitivity to deviations of natural image structure (Balas & Woods, 2014). We used event-related potentials (ERPs) to examine sensitivity to natural image statistics during childhood at distinct processing stages (the P1 and N1 components). We presented children (5-10 years old) and adults with natural images varying in positive/negative contrast, and natural/synthetic texture appearance to compare electrophysiological responses to images that did or did not violate natural statistics. We hypothesized that children would acquire sensitivity to these deviations late in middle childhood. Instead, we observed significant responses to unnatural contrast and texture statistics at the N1 in all age groups. At the P1, however, only young children exhibited sensitivity to contrast polarity. The latter effect suggests greater sensitivity earlier in development to some violations of natural image statistics. We discuss these results in terms of changing patterns of invariant texture processing during middle childhood and ongoing refinement of the representations supporting natural image perception.