Abstract
According to perceptual load theory (Lavie, 2005) distractor interference is determined by the availability of attentional resources. If target processing does not exhaust resources (low perceptual load) distractor processing will take place resulting with interference. Only when target processing uses-up attentional capacity (high perceptual load) interference can be avoided. As such, the theory stresses attentional factors (availability of attentional resources) in determining distractor interference. An alternative account (Dilution, Tsal, & Benoni, 2010) suggests that perceptual load effects might be explained by the mere presence of additional neutral items in high load displays (which typically involve set-size manipulation). These additional elements (as long as they have similar features as the distractor) may dilute the perceptual weight of distractor features. Accordingly, in displays with neutral items (similar to high load displays) but with easily discriminable targets (similar to low load displays) distractor interference is eliminated (Tsal & Benoni, 2010). Thus, dilution stresses low level perceptual factors as determining distractor interference in set size manipulations. One potential limitation of the dilution account is that even when targets are easily distinguished, attention might still be drawn to the neutral elements - consequently depleting resources so that distractor processing is prevented. To address this possible explanation we have tested a group of unilateral neglect patients. In neglect, low level perceptual processes are thought to be intact in the contralesional side while attentional capacity is damaged. Thus, by presenting neutral elements to the neglected side we were able to assess whether attentional or perceptual factors determine distractor interference. Our results indicate elimination of distractor interference when neutral elements are presented to the neglected side. We conclude that low level perceptual processes (rather than attention) underlie elimination of distractor interference in set size manipulation.