Visual attention and stimulus identification.

Previous research has provided evidence for parallel stimulus processing in visual search tasks; however, it has frequently been noted that detecting prespecified targets might be accomplished without actually identifying targets and/or distractors. A novel task was employed to require exhaustive identification: Subjects named the highest digit in an array. Reaction times and display size effects in this task were strikingly similar to the conventional search tasks reported here. Manipulation of display size and visual quality was used to test predictions of serial versus parallel encoding models. Display size was additive with two different visual quality factors in the highest digit task, a finding that argues against serial execution of the corresponding stages. Interactions with decision-related factors suggest that visual quality may have affected the rate of character recognition, not just feature extraction. Thus, various aspects of the results seem to strengthen the case for parallel (though perhaps capacity-limited) identification of multiple familiar stimuli. In the General Discussion, it is pointed out that parallel identification need not entail late selection, and some alternative possibilities are suggested.