Contextual modulations at low and high levels of visual perception: functional (in)dependence and influence of local contrast

Canoluk, Mehmet Umut [UCL] Grandjean, Marius [UCL] Goffaux, Valérie [UCL]

Spatial context modulates perception at low- and high levels of visual processing, with a shared dependence on the strength of the local input. In the case of human face perception, contextual modulations are presumed to rely on high-level, specialized mechanisms, with little contribution of low-level contextual mechanisms. Low- and high-level contextual modulations are typically studied independently, further obscuring their possible functional link. The present study will investigate whether consistent individual differences exist in contextual modulations at these two distinct levels of visual processing using contrast detection and facial feature discrimination tasks while manipulating the contrast (i.e., strength) of a local input target (local grating and facial feature, respectively). The context in the contrast detection task refers to a larger surrounding grating while in the facial feature discrimination task it refers to the facial features surrounding the target. The detection/discrimination contrast thresholds will provide a metric to evaluate contextual modulation magnitudes. By investigating the shared variance between the contextual modulation magnitudes across tasks, this study will provide insight into the functional relationship between low- and high-level contextual modulations and re-address the specificity of the contextual mechanisms at stake when processing faces in the light of low-level contextual modulations.