Academic journal article Perception and Psychophysics

Visual Search Is Not Blind to Emotion

Academic journal article Perception and Psychophysics

Visual Search Is Not Blind to Emotion

Article excerpt

A series of three visual search tasks revealed more efficient search for hostile than for peaceful faces among neutral face distractors. Given that this effect has been observed inconsistently in prior literature, meta-analytic methods were employed for evaluating data across three experiments in order to develop a more valid estimate of the potentially small effect size. Furthermore, in the present experiments, different emotional meanings were conditioned to identical faces across observers, thus eliminating confounds between the physical characteristics and the emotional valences of the face stimuli. On the basis of the present findings, we argue that the visual system is capable of determining a face's emotional valence before the face becomes the focus of attention, and that emotional valence can be used by the visual system to determine subsequent attention allocation. However, meta-analytic results indicate that emotional valence makes a relatively small contribution to search efficiency in the present search context.

Faces convey a wide range of valuable information to an observer. Ethologically, the emotional information conveyed by faces may be especially important because it may signal environmental threat. For example, an angry face might signal threat from an angry individual, or a fearful face may indicate a threat that another individual has detected. Given the meaningfulness of such information and the frequency with which it is encountered, one might expect a facial expression of emotion to be a valuable criterion for the allocation of attention (see, e.g., Hansen & Hansen, 1988; öhman, 1993).

Allocating attention to parts of a visual scene is necessary because our visual system cannot completely integrate, identify, or otherwise process every element of the environment each moment (see, e.g., Kahneman & Treisman, 1984; Tsotsos, 1997). The visual system must select, in an ongoing fashion, the elements that will receive limited processing resources. This selection must be guided by information that is already available to the system prior to the allocation of focal attention (Wolfe, 2003). Given these assumptions, the present work seeks to address two questions: Can the emotional valence effaces be perceived prior to the allocation of focal attention (i.e., preattentively)? If so, does it influence the subsequent allocation of focal attention? The present investigation employs the visual search task in order to address these questions.

The visual search task is commonly used to investigate the allocation of spatial attention. In this task, a target item is placed among a varying number of distractors, and its presence, location, or identity must be reported; this allows one to assess the effects of increasing the number of distractor items in the display. If finding a particular target does not require focal attention, its presence will be reported with the same ease, regardless of the number of distractors surrounding it. Such a target is said to "pop out" of the display (i.e., to be processed without attention, in parallel with distractor items, or preattentively) (see, e.g., Treisman & Gelade, 1980). However, searches for targets that do not possess this pop-out quality require additional time for each added distractor, because attention must be shifted among display items until the target is located. Thus, the slope of a function relating reaction time (RT) to the number of distractors is flat for items that pop out of their respective distractor contexts and is steeper for items that do not.

Although the presence of pop-out is commonly used in the visual search literature as a touchstone for preattentive or parallel processing, its value as the sole indicator of such processing is questionable. Parallel or preattentive processes involved in search may be accompanied by serial or postattentive processes, and therefore may be present in searches that do not show pop-out. …

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