Abstract
Behavioral research has demonstrated that the shape and the texture of a single object can be processed independently of each other (Cant et al., 2008). Consistent with this behavioral finding, neuroimaging results have shown that an object’s shape and texture are processed in distinct brain regions, with shape in the lateral occipital area and texture in parahippocampal cortex (Cant & Goodale, 2007). Meanwhile, objects in our environment are not always seen in isolation and there are ample instances in which multiple objects are grouped together as an ensemble (e.g. leaves on a tree). We recently showed that the processing of object ensembles also involves parahippocampal cortex (Cant & Xu, 2012) and that the shape and texture of ensemble elements are processed together within this brain region (Cant & Xu, VSS 2011). These neural data suggest that the independence seen between shape and texture processing in single-object perception would not be observed in object-ensemble perception. In the present study, we tested this prediction. Specifically, we examined whether observers could selectively attend to the shape of ensemble elements while ignoring changes in an unattended texture feature, and vice versa. Across five behavioral experiments, we replicated previous findings of independence between shape and texture processing in single objects, finding that changes in an unattended object feature did not affect the processing of an attended object feature. In contrast, we observed that changes in an unattended ensemble feature negatively impacted the processing of an attended ensemble feature, indicating that ensemble shape and texture are not processed independently, consistent with our prediction. Moreover, we found that processing ensemble feature changes more locally (similar to single-object processing) eliminated interference, whereas processing ensemble feature changes more globally produced interference. Taken together, these findings suggest that distinct cognitive and neural mechanisms are involved in single-object and object-ensemble perception.
Meeting abstract presented at VSS 2013