Category and word search: generalizing search principles to complex processing.

This research examines how the major phenomena of visual search for single characters generalize to word search and word-category search. Experiment 1 examined word and category visual search when the target and distractor sets had a varied mapping (VM) across trials. Reaction time was a linear function of the number of comparisons with a positive slope of 48 msec per word, 92 msec per category. The VM reaction time data indicated a self-terminating comparison process, and there was little or no improvement with practice. Experiment 2 examined search with a consistent mapping (CM) between targets and distractors. Category search slope dropped to 2 msec, and the function became nonlinear. Word search slope dropped to 18 msec, but the function became nonlinear. Word search slope dropped to 18 msec, but the function was still linear. Experiment 3 examined category detection carried out concurrently with serial recall of digits, allowing assessment of search performance under high workload. High workload caused a severe performance reduction in VM category search, and this decrement did not decrease with practice. High workload reduced initial performance in CM category search, but this decrement was eliminated with practice. The present category search results are similar to previous letter search results. Four principles of search are discussed in the context of a theory of automatic/control processing.