Abstract
Two experiments are reported that further explore the processes underlying dynamic search. In Experiment 1, observers’ oculomotor behavior was monitored while they searched for a randomly oriented T among oriented L distractors under static and dynamic viewing conditions. Despite similar search slopes, eye movements were less frequent and more spatially constrained under dynamic viewing relative to static, with misses also increasing more with target eccentricity in the dynamic condition. These patterns suggest that dynamic search involves a form of sit-and-wait strategy in which search is restricted to a small group of items surrounding fixation. To evaluate this interpretation, we developed a computational model of a sit-and-wait process hypothesized to underlie dynamic search. In Experiment 2 we tested this model by varying fixation position in the display and found that display positions optimized for a sit-and-wait strategy resulted in higher d′ values relative to a less optimal location. We conclude that different strategies, and therefore underlying processes, are used to search static and dynamic displays.
Highlights
We often search for things in static displays, situations in which the elements of the scene through which we are searching remain in the same locations over time
The hypothesis that distractor memory is used during search was challenged most directly by Horowitz and Wolfe (1998), who had observers search displays in which items either retained their locations throughout a trial or were randomly relocated every 111 ms
A memory-driven search process predicts that in the dynamic condition, search should be less efficient than in the static condition because any visual markers (e.g., Watson and Humphreys, 1997) set to item locations in frame n of a dynamic display would not be valid in frame n + 1, leading to the resampling of items and less efficient search
Summary
We often search for things in static displays, situations in which the elements of the scene through which we are searching remain in the same locations over time. As noted by Alvarez et al (2007), object motion and changes in the observer’s viewpoint can result in objects changing location abruptly and unexpectedly during search, an observation that casts doubt on the theoretical assumption of a memory for rejected distractors. The hypothesis that distractor memory is used during search was challenged most directly by Horowitz and Wolfe (1998) (see Smith and Henderson, 2011), who had observers search displays in which items either retained their locations throughout a trial (the static condition) or were randomly relocated every 111 ms ( referred to as the “dynamic condition”). Horowitz and Wolfe (1998) found that search efficiency was comparable in the two display conditions and concluded that memory was not used during search of static displays, despite its availability
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