Hooge I T C, Vlaskamp B N S, Over E A B, 2002, "Saccadic search: the relation between fixation duration and saccade amplitude" Perception 31 ECVP Abstract Supplement
Saccadic search: the relation between fixation duration and saccade amplitude
I T C Hooge, B N S Vlaskamp, E A B Over
In most large search displays a number of fixations is required to find a target. The size of the area that can be inspected during a single fixation increases with time (Geisler and Chou, 1995 Psychological Review 102 356 - 378), indicating that fixation time and saccade amplitude should correlate. This suggests that observers may adopt various search strategies (eg short fixation times and small saccade amplitudes or long-lasting fixations and large saccades). It is also known that visual processing time increases with search-task difficulty. Thus when task difficulty is varied, subjects may adjust fixation time, saccade amplitude, or both. However, how do subjects adjust saccade amplitude and fixation time to the demands of a search task? Subjects were instructed to find one circle (the target) among many Cs in a large stimulus (40 deg × 30 deg). In 12 sessions we varied the number of elements (36, 64, 100, or 144) and gap size in the C (0.095, 0.19, or 0.38 deg; element size is 0.76 deg). Search strategies of all subjects were similar. Fixation time decreased and saccade amplitude increased with increasing gap size and increasing element distance. Of all hypothetical search strategies, fixation time increased with decreasing saccade amplitude irrespective of task difficulty.
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