Visual search paradigms, in which the subject attempts to find a particular stimulus in a display of N stimuli, have been used extensively to study attention and automatism. Separating attentive and automatic processes has proved difficult (for one summary, see Shiffrin, 1988), and the number of proposed theories and mechanisms has not lagged far behind the number of studies. One approach to separating these processes, used in the research reported in this chapter, involves extended training. The general idea is that attentive limitations are resistant to training effects, but automatic processes can be learned in appropriate seffings.
Although stimulus characteristics and training can both play important roles in driving each of attentive and automatic visual search, theories can be classified usefully on the basis of which of these factors is emphasized.