Abstract
Inhibition of return (IOR) has been proposed as an attentional mechanism which facilitates visual search by inhibiting reorienting to previously attended spatial locations. IOR is typically measured following the removal of attention from a spatial location. Early facilitation of responses to this location at early stimulus-onset asynchrony (SOA of ∼100 – 300ms) is replaced with a later and long-lasting inhibition (SOA of ∼300 – 3000ms). This inhibition has been proposed to be used by the oculomotor system to tag previously fixated locations in visual search to favour new locations over old (yet still salient) locations. Indeed, slower responses to probes presented in recently fixated locations has since been demonstrated in a variety of visual search tasks, and this form of IOR has been related to the reduced likelihood of refixating the previous or penultimate search location during natural search (MacInnes and Klein, 2003). However, recent research has challenged this interpretation by suggesting that saccadic momentum facilitates forward saccades as opposed to IOR suppressing return saccades. For instance, Smith and Henderson (2010) replicated Klein and MacInnes (1999) by finding IOR in a Where's Waldo © search task, but they reanalyzed the probability distribution of saccades to provide evidence for a saccadic momentum account. This talk will provide a review of recent research outlining the evidence for IOR and saccadic momentum in natural search patterns and present new data on the distribution of saccades in complex search tasks. [Supported by BBSRC]