Abstract
Recent evidence from tasks like multiple object tracking (Alvarez & Cavanagh, 2005), crowding (Chakravarthi & Cavanagh, 2009) or number estimation (Delvenne et al., 2011) suggests superior visual processing of bilaterally compared to unilaterally presented information. This bilateral field advantage is interpreted as evidence for basic anatomical constraints on attentional selection of perceptual information. In order to critically evaluate the level of processing of this bilateral benefit we presented up to 6 items in an enumeration task using a forward masking paradigm (Di Lollo, 1980). On each trial, the targets were presented either in a single hemifield or in both hemifields. We had previously reported that the forward masking procedure fractionated the duration of visible persistence of the target items, allowing us to measure the time course of object individuation. Processing capacity was found to be a direct consequence of the time window of access to sensory information (Wutz, Caramazza & Melcher, ECVP 2011.). We hypothesized that if the bilateral field advantage reflects early visual constraints on object selection—based on independent resources within each hemisphere—then the rate of object individuation should be more rapid with bilateral presentation of the items. However, the rate of object individuation, as well as overall capacity, was identical with lateralized or bilateral presentations of the targets. Our results therefore support a later locus of the bilateral field advantage in attentional selection within high-level visual processes, perhaps limited to top-down deployment of attention.
Meeting abstract presented at VSS 2012