Selective attention and the perception of an attended nontarget object

Both feature comparisons and location comparisons are subject to bias

Four experiments explore the generalizability of two different types of bias in visual comparison. The first type is a spatial congruency bias, in which two target stimuli are more likely to be classified as matching ('same') if they appear successively at the same location. The second type is an analytic bias, which varies depending on the overall similarity of the displays and the need to select specific parts from each object. Both types of bias had previously been demonstrated in comparisons based on shape and other visual features. The current tasks move beyond feature comparisons, requiring the comparison of the local positions of visual elements (dots or letters) that appear within each pattern. Given the privileged role of location in visual representations and attentional selection, it is important to test how visual comparisons of location differ from comparisons of shape and other features. The spatial congruency bias is replicated in the comparison of local positions and, as in previous experiments, its strength diminishes when the displays being compared are less similar to one another. Also, as demonstrated previously with letter comparisons, there is an analytic bias shifting responses toward 'different' when the displays being compared are less similar to one another. Responses are also shifted more toward 'same' in location comparisons relative to feature comparisons. The general pattern of results suggests that as more attentional selection is required in a comparison task, there is a stronger overall bias to respond 'different'.

Measurement of auditory cues in drivers' distraction

A driving simulator was used to examine the effects on driving performance of auditory cues in an in-vehicle information search task. Drivers' distraction by the search tasks was measured on a peripheral detection task. The difficulty of the search task was systematically varied to test the distraction caused by a quantified visual load. 58 participants completed the task. Performance on both search tasks and peripheral detection tasks was measured by mean response time and percent error. Analyses indicated that in-vehicle information search performance can be severely degraded when a target is located within a group of diverse distractors. Inclusion of an auditory cue in the visual search increased the mean response time as a result of a change in modality from auditory to visual. Inclusion of such an auditory cue seemed to influence distraction as measured by performance on the peripheral detection task; accuracy was lower when auditory cues were provided, and responses were slower when no auditory cues were provided. Distraction by the auditory cue varied according to the difficulty of the search task.

Temporal dissociation between category-based and item-based processes in rejecting distractors

Presenting a target-like distractor in an RSVP task deteriorates the detection of a trailing target, because the visual system has difficulties in rejecting the erroneously accepted distractor. We investigated whether the rejection process is influenced by observers' knowledge regarding possible distractors. Observers identified a letter (target) embedded in a stream of line patterns, rejecting a preceding distractor (digit). We informed the observers about either the category of distractors ("digit") or the identity of the distractor (e.g., "5"). The distractors with certain distractor-target lags increased identification errors, indicating that the distractor rejection process temporarily interfered with the target identification. When the observers knew the distractor identity, the rejection process started later than when they knew only the distractor category. These results suggest that the rejection process may operate at either the category or the individual-item level; however, the setting of the rejection level is not under the observers' control.