Abstract
Top-down search templates specify targets’ properties, either to guide attention toward the target or, independently, to accelerate the recognition of individual search items. Some previous studies have concluded that target templates can specify semantic categories to guide attention, though dissociating the effects of semantic versus visual features has proven difficult. In the present experiments, we examined the roles of target templates in search performance, by measuring the “two-template costs” incurred when observers did not know which of two types of targets would be presented. For target templates, these costs only varied with set size when a template could specify a target’s features. Any semantic influences did not affect the guidance of attention, only the recognition of individual items. In contrast, templates for rejection—specifying the properties of irrelevant nontargets—do appear to specify semantic properties to guide attention away from those items, without affecting recognition. These qualitative differences between the two types of templates suggest that the processes of seeking and ignoring are fundamentally different.
Highlights
Top-down search templates specify targets’ properties, either to guide attention toward the target or, independently, to accelerate the recognition of individual search items
For example, an observer wishes to detect a person in a natural scene, can their search template only bias attention toward the target by specifying human beings’ visual features, or can their template specify those objects’ semantic properties to guide attention? This ambiguity does not arise for many conventional visual search studies, which examine search for simple abstract images, but it is prominent in heterogeneous and complex naturalistic object images
Such conclusions challenge influential models of search (e.g., Wolfe, Alvarez, Rosenholtz, Kuzmova, & Sherman, 2011) that have assumed that search templates guide attention by specifying bundles of visual features associated with targets
Summary
Many Breal-world^ search tasks involve search for a category of objects—keys, fruit, shoes—rather than for a specific target object image. Our brief survey of the literature, outlined above, convinced us that, the balance of evidence was consistent with the notion that target templates could guide search by specifying semantic features, substantial further support would need to be garnered to establish this securely To address this issue, here we employed a Bbarebones^ version of Wolfe and colleagues’ hybrid search task (e.g., Wolfe, 2012), in which the key displays comprised just two items—one target object and one nontarget. A striking feature of two-template costs in relation to templates for rejection was their absence in oneitem displays, even for unrelated categories of targets— reflecting changes in the guidance of attention, rather than in the recognition of (non)targets as such In this set of experiments, we applied that same logic to the study of target search templates, which specify the properties of targets in order to enhance guidance of attention toward those objects and speed recognition of them as targets. Nontargets in these studies could be any image other than the potential target categories (a shoe, book, chair, etc.)
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