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Abstract Eye movements were monitored while subjects performed parallel and serial search tasks. In Experiment la, subjects searched for an "O" among "X"s (parallel condition) and for a "T" among "L"s (serial condition). In the parallel condition of Experiment lb, ""Symbol not transcribed"" was the target and ""Symbol not transcribed""s were distractors; in the serial condition, these stimuli switched roles. Displays contained 1, 12, or 24 stimuli, with both target-present and target-absent trials. RT and eye-movement measures (number of fixations, saccadic error, and latency to move) indicated that search efficiency was greatest in the parallel conditions, followed by the serial condition of Experiment 1a and, finally, by the serial condition of Experiment 1b. This suggests that eye movements are correlated with the attentional processes underlying visual search. How are we able to visually search through our complex environment to find a particular item that we need or want? For example, how are we able to find a pen lying amid papers and books on a cluttered desk? Furthermore, while conducting this search, how do we know that a particular feature in the visual array (e.g., "redness") belongs to one object (e.g., the pen) and not to another (e.g., a book)? Studies attempting to address such questions have made extensive use of the visual search task. In this paradigm, subjects are asked to search stimulus displays for a target among distractors. Typically, both display size (i.e., number of stimuli) and trial type (target present vs. target absent) vary across trials. A target stimulus in a visual search task may be defined either by a distinct feature (feature search task) or by a particular combination or conjunction of features (conjunction search task). For example, in a feature search task, subjects might be asked to look for a red "O" among blue and green "O"s. Here, the target's colour is a unique feature which distinguishes it from the distractors. In a conjunction search task, the target stimulus might be the same red "O," but this time, the distractors could be blue "O"s and red "X"s. In this case, each distractor shares at least one feature with the target, such that the target can only be defined by a specific conjunction of colour and shape. In feature search tasks,...