Impaired global, and compensatory local, biological motion processing in people with high levels of autistic traits

People with Autism Spectrum Disorder (ASD) are hypothesized to have poor high-level processing but superior low-level processing, causing impaired social recognition, and a focus on non-social stimulus contingencies. Biological motion perception provides an ideal domain to investigate exactly how ASD modulates the interaction between low and high-level processing, because it involves multiple processing stages, and carries many important social cues. We investigated individual differences among typically developing observers in biological motion processing, and whether such individual differences associate with the number of autistic traits. In Experiment 1, we found that individuals with fewer autistic traits were automatically and involuntarily attracted to global biological motion information, whereas individuals with more autistic traits did not show this pre-attentional distraction. We employed an action adaptation paradigm in the second study to show that individuals with more autistic traits were able to compensate for deficits in global processing with an increased involvement in local processing. Our findings can be interpreted within a predictive coding framework, which characterizes the functional relationship between local and global processing stages, and explains how these stages contribute to the perceptual difficulties associated with ASD

A single motion system suffices for global-motion perception

AbstractGlobal-motion perception is the perception of coherent motion in a noisy motion stimulus. Thresholds for coherent motion perception were measured for different combinations of signal and noise speeds. Previous research [Edwards, M., Badcock, D. R., & Smith, A. T. (1998). Independent speed-tuned global-motion systems. Vision Research, 38 (11), 1573–1580; Khuu, S. K., & Badcock, D. R. (2002). Global speed processing: evidence for local averaging within, but not across two speed ranges. Vision Research, 42 (28), 3031–3042.] showed that thresholds were elevated when signal and noise speeds were similar, but not when they were different. The regions of increased threshold values for low and high signal speeds showed little overlap. On the basis of this evidence two independent speed-tuned systems were proposed: one for slow and one for fast-motion. However, in those studies only two signal speeds were used. We expanded the results by measuring threshold-curves for four different signal speeds. Considerable overlap of the threshold-curves was found between conditions. These results speak against a bipartite global-motion system. Model simulations indicate that present and previous experimental results can be produced by a single motion system providing that the mechanisms within it are speed-tuned

Perception of plane orientation from self-generated and passively observed optic flow

Soumis à Journal of Vision (2002)We investigate the perception of 3D plane orientation—focusing on the perceptionof tilt—from optic flow generated by the observer's movement around a simulatedstationary object, and compare the performance to that of an immobile observer receivinga replay of the same optic flow. We find that perception of plane orientationis more precise in the active than in the immobile case. In particular, in the caseof the immobile observer the presence of shear in optic flow drastically diminishesthe precision of tilt perception, whereas in the active observer this decrease in performanceis greatly reduced. Furthermore, perceived slant is better correlated withsimulated slant in the active observer. We conclude with a discussion of possiblesystematic biases in tilt perception from optic flow, as well as of various theoreticalexplanations for our results