Previous studies using hierarchical figures (where a large global shape is composed of a series of smaller local shapes) suggest that performance is better for local features presented in the right relative to left visual field, whereas the opposite pattern is observed for global features. However, these previous studies have focused on effects between hemifields. Recent data from patients with neurological damage suggest that local deficits can be allocentric (e.g., following left hemisphere injury, individuals are relatively slow to detect features on the right side of an object, regardless of visual field). Therefore, we decided to extend previous global versus local research by also observing local performance within hemifields. Specifically, on each trial we presented two hierarchical figures (one in each hemifield), but crucially the left and right side of each item were composed of different local features. In this task, the participant simply reports if a circle is present, regardless of location or whether this is a local or global feature. We observed that both neurologically healthy individuals, as well as an individual with brain injury, were relatively better detecting local information on the right side of objects, regardless of spatial location, while both showed better performance for global stimuli in the left visual field. This work is consistent with recent work in patients with neurological damage, and provides a new paradigm for exploring hemispheric specialization.
Keywords: spatial selection; visual attention.