Richard D. Wright

Location cue validity affects inhibition of return of visual processing.

Inhibition-of-return is the process by which visual search for an object positioned among others is biased toward novel rather than previously inspected items. It is thought to occur automatically and to increase search efficiency. We examined this phenomenon by studying the facilitative and inhibitory effects of location cueing on target-detection response times in a search task. The results indicated that facilitation was a reflexive consequence of cueing whereas inhibition appeared to depend on cue informativeness. More specifically, the inhibition-of-return effect occurred only when the cue provided no information about the impending targets location. We suggest that the results are consistent with the notion of two levels of visual processing. The first involves rapid and reflexive operations that underlie the facilitative effects of location cueing on target detection. The second involves a rapid but goal-driven inhibition procedure that the perceiver can invoke if doing so will enhance visual search performance.

Effect of a concurrent auditory task on visual search performance in a driving-related image-flicker task

The effect of a concurrent auditory task on visual search was investigated using an image-flicker technique. Participants were undergraduate university students with normal or corrected-to-normal vision who searched for changes in images of driving scenes that involved either driving-related (e.g., traffic light) or driving-unrelated (e.g., mailbox) scene elements. The results indicated that response times were significantly slower if the search was accompanied by a concurrent auditory task. In addition, slower overall responses to scenes involving driving-unrelated changes suggest that the underlying process affected by the concurrent auditory task is strategic in nature. These results were interpreted in terms of their implications for using a cellular telephone while driving. Actual or potential applications of this research include the development of safer in-vehicle communication devices.

Inhibition-of-return at multiple locations in visual space.

Inhibition-of-return is thought to be a visual search phenomenon characterized by delayed responses to targets presented at recently cued or recently fixated locations. We studied this inhibition effect following the simultaneous presentation of multiple location cues. The results indicated that response inhibition can be associated with as many as four locations at the same time. This suggests that a purely oculomotor account of inhibition-of-return is oversimplified. In short, although oculomotor processes appear to play a role in inhibition-of-return they may not tell the whole story about how it occurs because we can only program and execute eye movements to one location at a time.

Polarity matching in the Ternus configuration

Two experiments were conducted to examine the effect of changes in the sign of element contrast on perceptions of the Ternus apparent motion display. In the first experiment, the contrast polarity of all three elements in the display were alternated from the first frame of view to the second. At short durations, this increased perceptions (relative to a control condition) of simultaneity in the display, decreased perceptions of element motion, and did not significantly affect perceptions of group motion. At long durations, this manipulation did not affect performance. In a second experiment, patterns of element polarity were manipulated to favour perceptions of either element motion or of group motion relative to a control condition in which all elements had identical contrast polarity. At a long duration, this manipulation affected perceptions of the configuration; this manipulation did not affect the appearance of the display at a short duration. Together, these results are inconsistent with the predictions of Grossberg and Rudds [Psychological Review, 99, 78-121 (1992)] motion oriented contrast filter. However, they are consistent with a model of motion correspondence processing that includes a polarity matching constraint.

Sensory mediation of stimulus-driven attentional capture in multiple-cue displays

Three location-cuing experiments were conducted in order to examine the stimulus-driven control of attentional capture in multiple-cue displays. These displays consisted of one to four simultaneously presented direct location cues. The results indicated that direct location cuing can produce cue effects that are mediated, in part, by nonattentional processing that occurs simultaneously at multiple locations. When single cues were presented in isolation, however, the resulting cue effect appeared to be due to a combination of sensory processing and attentional capture by the cue. This suggests that the faster responses produced by direct cues may be associated with two different components: an attention-related component that can be modulated by goal-driven factors and a nonattentional component that occurs in parallel at multiple direct-cue locations and is minimally affected by goal-driven factors.

Goal-driven modulation of stimulus-driven attentional capture in multiple-cue displays

Six location-cuing experiments were conducted to examine the goal-driven control of attentional capture in multiple-cue displays. In most of the experiments, the cue display consisted of the simultaneous presentation of a red direct cue that was highly predictive of the target location (the unique cue) and three gray direct cues (the standard cues) that were not predictive of the location. The results indicated that although target responses were faster at all cued locations relative to uncued locations, they were significantly faster at the unique-cue location than at the standard-cue locations. Other results suggest that the faster responses produced by direct cues may be associated with two different components: an attention-related component that can be modulated by goal-driven factors and a nonattentional component that occurs in parallel at multiple direct-cue locations and is minimally affected by the same goal-driven factors.

Simultaneity in the Ternus configuration: psychophysical data and a computer model

The Ternus configuration is an apparent motion display which is typically described as being bistable; subjects usually describe seeing either element motion or group motion, depending upon temporal properties of the display. The results of an experiment are reported in which subjects are also permitted to report seeing four stationary display elements (simultaneity). It was found that simultaneity was produced when both frame durations and interstimulus intervals (ISIs) were brief. A weaker than expected effect of stimulus onset asynchrony (SOA) was revealed because this third type of judgment was obtained. Furthermore, statistical analyses indicated that SOA was not by itself the best predictor of judgment type. The interaction between duration and ISI was also an important predictor. This suggested that a complete account of the Ternus configuration requires two mechanisms: a visible persistence mechanism, governed by an SOA law, and a motion correspondence mechanism, governed by an ISI law. These two mechanisms were added to Dawsons (1991) [Psychological Review, 98, 569-603] autoassociative network for motion correspondence processing. The resulting model could generate each of the three interpretations of the Ternus configuration at appropriate combinations of frame duration and ISI.

Neutral location cues and cost/benefit analysis of visual attention shifts.

The effects of location cuing on target responses can be examined by comparing informative and neutral cuing conditions. In particular, the magnitudes of costs of invalid location cuing and of benefits of valid location cuing can be determined by comparing invalid and valid cue responses to location-nonspecific neutral cue responses. Cost/benefit analysis is based on the assumption that neutral baseline measures reflect a general warning effect about the impending targets onset but no other specific target information. The experiments we report were carried out to determine the appropriateness of two baseline measures for cost/benefit analyses of direct (nonsymbolic) location cuing effects. We found that a multiple-cue baseline attenuated the benefits of valid cuing, and that a background-flash baseline arbitrarily attenuated costs or benefits depending on flash intensity. It is proposed that a background flash is the more suitable neutral cue because it is target-location-nonspecific, but that its intensity should be adjusted to elicit a target-onset warning signal of the same magnitude as the location cues with which it will be compared.

Inhibition of Return to an Occluded Object Depends on Expectation

Inhibition of return (IOR) is indexed by slower reaction times to targets presented at previously attended locations or objects. If a moving object is occluded, some studies find IOR, others do not. Four experiments examined whether this inconsistency hinges on the observers expectation as to whether the object continues to exist at the end of its motion sequence. Results showed that observer expectation is a powerful determining factor: IOR occurs only if the observer expects the object to continue to exist. In contrast, if the object is not occluded, IOR occurs only if the object remains on view immediately before the target is presented. It was concluded that 2 factors, object continuity and observer expectation, mediate both location- and object-based IOR.

Inattention and the perception of visual features.

Subjects selectively attended to one of two interleaved, novel figures while ignoring the other figure. In subsequent tests administered to determine the extent to which the ignored figure was perceived, recognition of shape and the location of contour gaps was at the chance level. Moreover, recognition of the presence of contour gaps was significantly below the chance level. These results indicate that preattentive visual processing of unattended objects is too crude to encode global shape and local features such as contour gaps. It is suggested that preattentive processing creates visual representations of unattended objects that contain very limited information about features.