In the glimpse of an eye : decision making and vision

Rapid visual search, depending on iconic memory, is a core but controversial psychophysical topic. A key example is the claim by Horowitz & Wolfe (1998a) that ‘visual search has no memory. Their evidence is the effect of increasing search set size in a letter identification task. Search time per item was unimpaired when all letters were randomly relocated during the search. This paper presents additional analyse showing strong deleterious effects of randomly relocating letters, on error rates, and on total reaction time. Thus visual search does have a memory. A psychophysical information accrual model is presented to account for these data and other key studies on visual search. The model includes decision criteria as well as sensory parameters. Criterion adjustments, which depend on numbers of distractors, predict the lower mean search times and the lower error, rates observed for non-random presentations.