Academic journal article Perception and Psychophysics

Direct Selection by Color for Visual Encoding

Academic journal article Perception and Psychophysics

Direct Selection by Color for Visual Encoding

Article excerpt

In two experiments, we used rapid serial visual presentation tasks to examine the usefulness of color for the direct selection of visual information for perceptual encoding. The participants' task was to make a discrimination as to whether a target letter within a rapid sequence appeared in its upper- or lowercase version, and an advance cue indicated the color in which the target letter was most likely to occur. To maximize the usefulness of the cued color, in validly cued trials, we used sequences in which the target was the only item appearing in the cued color. In both experiments, accuracy was highest for validly cued trials. A cost-benefit analysis revealed a facilitory effect of valid cues and an inhibitory effect of invalid ones. These results support the idea that color cuing allows the direct selection of objects for further perceptual processing.

When we look for a target object in a visual scene, we often need to be able to single out or select that object so that it can be processed further once it is found. One interesting question regarding this selection process is to consider what types of information can guide it. Within research on selective attention, a common method for examining this question is to provide a cue giving an observer advance knowledge about some aspect of the target object or the setting in which it will appear. If the cue aids selection, then the information it provided must have been useful in guiding selection.

Researchers have examined several types of cuing information to determine their potential benefits for selection, and the results clearly indicate that spatial information is the most useful. In one study, for example, Posner, Snyder, and Davidson (1980) asked their participants to respond rapidly to the onset of any one of four light-emitting diodes. Prior to stimulus onset, the participants were given a cue indicating the likely location of the target diode onset. Responses were faster when the cue was correct (valid cue trials) than when it was incorrect (invalid cue trials). Thus, a location cue allows participants to attend selectively to the indicated location, so a target can be detected better at that location than at uncued locations. Similar results have been reported in paradigms in which identification tasks (Cheal & Gregory, 1997) and discrimination tasks (Theeuwes, 1989), rather than simple detection tasks, such as that in Posner et al., have been used. In short, a variety of results have provided evidence that location cues offer significant benefits for selection.

Color is another feature that has been examined for its capacity to aid selection. The results of studies in which target color was cued have indicated that advance color cues generally provide some selection advantage, although not as much as location cues. For example, Carter (1982) presented search displays consisting of multiple three-digit numbers. Participants had to find the three-digit number beginning with two specified target digits and then report the third digit within that number. Responses were faster when the color of this number was cued than when it was not. Carter also manipulated the number of items with the cued color while keeping the total display size constant, and he found that search times varied according to the number of items in the cued color but were largely independent of the number of items in the other colors. Similar results have been reported for tasks in which letter discrimination (LaBerge & Brownston, 1974) and search for two-digit numbers (Green & Anderson, 1956) were used. Thus, these results clearly demonstrate that color cues can aid selection by defining a subset of items for selective processing.1

Is Selection by Color Completely Mediated by Location?

Although it is quite clear that color information can be used to guide selection, it is less clear how it does so. At one extreme is the possibility that the advantage for items in a cued color is mediated entirely by location. …

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