Academic journal article Attention, Perception and Psychophysics

Hiding and Finding: The Relationship between Visual Concealment and Visual Search

Academic journal article Attention, Perception and Psychophysics

Hiding and Finding: The Relationship between Visual Concealment and Visual Search

Article excerpt

As an initial step toward developing a theory of visual concealment, we assessed whether people would use factors known to influence visual search difficulty when the degree of concealment of objects among distractors was varied. In Experiment 1, participants arranged search objects (shapes, emotional faces, and graphemes) to create displays in which the targets were in plain sight but were either easy or hard to find. Analyses of easy and hard displays created during Experiment 1 revealed that the participants reliably used factors known to influence search difficulty (e.g., eccentricity, target-distractor similarity, presence/absence of a feature) to vary the difficulty of search across displays. In Experiment 2, a new participant group searched for the targets in the displays created by the participants in Experiment 1. Results indicated that search was more difficult in the hard than in the easy condition. In Experiments 3 and 4, participants used presence versus absence of a feature to vary search difficulty with several novel stimulus sets. Taken together, the results reveal a close link between the factors that govern concealment and the factors known to influence search difficulty, suggesting that a visual search theory can be extended to form the basis of a theory of visual concealment.

Since 9/11, there has been a growing focus on increasing security in public places such as airports. Laboratory research on this security issue has tended to capitalize on a large body of work examining how people visually search for a target object embedded among a set of distractor objects (e.g., Bundesen, 1990; Duncan & Humphreys, 1989; Treisman & Gelade, 1980; Wolfe, 1994; Wolfe, Cave, & Franzel, 1989). In these studies, participants are typically required to search for a target that is placed in plain sight among a group of distractor items. Table 1 presents a summary of some of the factors that have been shown to influence search, together with a description of the influence.

Naturally, the act of visual search often requires searching for something that is hidden. Despite this close interrelationship between hiding and search, research has focused almost entirely on the act of search. Here, we explore the related act of hiding and take some initial steps toward developing a psychological theory of concealment. Our specific hypothesis was that because hiding and search are logically closely coupled, the basic principles that govern how people hide objects will be closely related to the basic principles that govern visual search.

We began by evaluating whether naive participants would use the same factors that have been shown to govern search difficulty when they were required to arrange objects in a manner that they believed would make a target either easy or hard to find. To closely match the visual search literature, which involves finding objects in plain sight, we focused on the concealment of objects in plain sight (i.e., without occlusion). In Experiment 1, participants were asked to complete a placement task in which they had to create visual search displays such that a target would be either easy or hard to find. In this task, the participants were given three stimulus sets (see Figure 1) and were asked to place the objects on a display surface such that the target was either easy or hard to find. Each of the stimulus sets was chosen because it had previously been employed in studies of search. The first stimulus set, the asymmetry-shape set, was composed of a circle and a circle with a line through it and has been used in previous studies of visual search that evaluated how the presence or absence of a single visual feature influences search difficulty (see Treisman & Gormican, 1988; Treisman & Souther, 1985). The second stimulus set, the affective-face set, which included three different affective faces, has been used in studies of emotional valence in visual search (see Eastwood, Smilek, & Merikle, 2001; Fox et al. …

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