Oblique Orientation Discrimination Thresholds Are Superior in Those with a High Level of Autistic Traits

Enhanced low-level perception, although present in individuals with autism, is not seen in individuals with high, but non-clinical, levels of autistic traits (Brock et al. in Percept Lond 40(6): 739. doi: 10.1068/p6953, 2011). This is surprising, as many of the higher-level visual differences found in autism have been shown to correlate with autistic traits in non-clinical samples. Here we measure vertical-oblique and, more difficult, oblique-oblique orientation discrimination thresholds in a non-clinical sample. As predicted, oblique-oblique thresholds provided a more sensitive test of orientation discrimination, and were negatively related to autistic traits (N = 94, r = -. 356, p <. 0001). We conclude that individual differences in orientation discrimination and autistic traits are related, and suggest that both of these factors could be mediated by increased levels of the inhibitory neurotransmitter GABA.