Abstract
In the present study, we examine how observers search among complex displays. Participants were asked to search for a big red horizontal line among 119 distractor lines of various sizes, orientations and colours, leading to 36 different feature combinations. To understand how people search in such a heterogeneous display, we evolved the search display by using a genetic algorithm (Experiment 1). The best displays (i.e., displays corresponding to the fastest reaction times) were selected and combined to create new, evolved displays. Search times declined over generations. Results show that items sharing the same colour and orientation as the target disappeared over generations, implying they interfered with search, but items sharing the same colour and were 12.5° different in orientation only interfered if they were also the same size. Furthermore, and inconsistent with most dominant visual search theories, we found that non-red horizontal distractors increased over generations, indicating that these distractors facilitated visual search while participants were searching for a big red horizontally oriented target. In Experiments 2 and 3, we replicated these results using conventional, factorial experiments. Interestingly, in Experiment 4, we found that this facilitation effect was only present when the displays were very heterogeneous. While current models of visual search are able to successfully describe search in homogeneous displays, our results challenge the ability of these models to describe visual search in heterogeneous environments.
Highlights
Visual search is a widely used task to study visual attention
From the decline in reaction time (RT) over generations, it appears likely that the genetic algorithm was successful in changing the distractor sets to make participants faster at the visual search task
Since the genetic algorithm decides the evolution based on the RTs within a generation, the evolution is not affected by such effects
Summary
Visual search is a widely used task to study visual attention. This approach has revealed much about how we search for a target among distractors. Van der Burg, Cass, Theeuwes & Alais [7] recently used the genetic algorithm as an atheoretical, unbiased method to reveal people’s visual search behaviour by evolving a complex visual search display towards faster-searched displays They used a display made up of 72 distractor lines of three orientations (0°, 10° or 90°) and 3 colours (red, green or blue). The results showed a concomitant increase in the number of horizontal lines over successive generations, indicating that they facilitated faster visual search times for the red horizontal target This latter finding is counterintuitive, it is the opposite of what has been observed in previous studies exploring the role of irrelevant distractors [12,13,14,15,16,17]. If the increase in non-red horizontal distractors in the Van der Burg et al, study was due to other distractors decreasing, we expect to find an increase in the non-red horizontal distractors that is in line with the increase in other non-detrimental distractors, as there are more feature combinations to spread this decrease over
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