When sustained attention impairs perception

Vision Research, 1989

We measured the detectability of a target pattern in a display consisting of 12 elements in a circle around the central fixation point. The display was presented briefly and followed after a variable amount of time by a mask. We found that presenting a pre-cue, designating the target position, facilitated target detectability. Attention is directed to the cued location. When the observer has to detect a (second) target among the non cued elements, performance for locations close to the cue is not significantly different from performance for locations further away. This suggests that there is no "scan-path" or proximity effect. We also found that the identification of the cued element delayed the detectability of the subsequent target by more than 160 msec. In another series of experiments we studied the control of attentional shifts. We found that, for short mask delays (100, 160 and 260 msec) the observer is unable to selectively process elements which are not physically cued but only verbally defined by their position relative to the cue. When we increase the positional uncertainty of the target by increasing the number of physical cues, performance drops until it reaches an asymptote with 5 elements. We infer that, even though the target is very similar to the background, a parallel mechanism, used for the extraction of stimulus features, designates prospective target locations which may be subsequently checked by a (slow) attentional process.

Cognition, 2008

When our attention is engaged in a visual task, we can be blind to events which would otherwise not be missed. In three experiments, 97 out of the 165 observers performing a visual attention task failed to notice an unexpected, irrelevant object moving across the display. Surprisingly, this object significantly lowered accuracy in the primary task when, and only when, it failed to reach awareness. We suggest that an unexpected stimulus causes a state of alert that would normally generate an attentional shift; if this response is prevented by an attention-consuming task, a portion of the attentional resources remains allocated to the object. Such a portion is large enough to disturb performance, but not so large that the object can be recognized as task-irrelevant and accordingly ignored. Our findings have one counterintuitive implication: irrelevant stimuli might hamper some types of performance only when perceived subliminally. 

Vision Research, 2004

Observers often fail to detect the appearance of an unexpected visual object (''inattentional blindness''). Experiment 1 studied the effects of fixation position and spatial attention on inattentional blindness. Eye movements were measured. We found strong inattentional blindness to the unexpected stimulus even when it was fixated and appeared in one of the expected positions. The results suggest that spatial attention is not sufficient for attentional capture and awareness. Experiment 2 showed that the stimulus was easier to consciously detect when it was colored but the relation of the color to the color of the attended objects had no effect on detection. The unexpected stimulus was easiest to detect, when it represented the same category as the attended objects.

A critical question for understanding the relationship between attention and awareness is whether attentional selection can occur in the absence of awareness . Specifically, does allocation of attention to an invisible event impact the neural substrates responding to that event? By`invisible event' we refer to a visual stimulus that the observer is exposed to but (i) has no subjective impression of and (ii) performs at chance if obliged to guess about some aspect of its content, eg orientation.

Perception & Psychophysics, 1969

A ttentional demands were varied in a two-alternative, forced-choice detection experiment. A bar indicator designated the target form in one condition and occurred in random locations in a second condition. Exposure durations necessary for predetermined single-form display HRs were determined for each of eight Ss to measure performance at different levels of perceptual system error. Forms differed in only a single feature. Detection was superior when the bar indicator designated the target form, and differences increased with increased display size. Evidence for interference in detection due to the presence of nontarget forms apart from noting requirements of such forms was found. Estimates of number of perceptual channels noted did not clearly differentiate serial from parallel processing models. It was concluded that display interference error and spatial selectivity influences are important determinants of detection accuracy.

Perception, 2008

110

Quarterly Journal of Experimental Psychology, 2009

We propose that voluntary and involuntary attention affect different mechanisms and have different consequences for performance measured in reaction time. Voluntary attention enhances the perceptual representation whereas involuntary attention affects the tendency to respond to stimuli in one location or another. In a spatial-cueing paradigm, we manipulated perceptual difficulty and compared voluntary and involuntary attention. For the voluntary-attention condition, the spatial cue was predictive of the target location, whereas in the involuntary-attention condition it was not. Increasing perceptual difficulty increased the attention effect with voluntary attention, but decreased it with involuntary attention. Thus voluntary and involuntary attention have different consequences when perceptual difficulty is manipulated and hence are probably caused by different mechanisms.

1995

The early and late selection debate may be resolved if perceptual load of relevant information determines the selective processing of irrelevant information. This hypothesis was tested in 3 studies; all used a variation of the response competition paradigm to measure irrelevant processing when load in the relevant processing was varied. Perceptual load was manipulated by relevant display set size or by different processing requirements for identical displays. These included the requirement to process conjunctions versus isolated features and the requirement to perform simple detection of a character's presence versus difficult identification of its size and position. Distractors' interference was found only under low-load conditions. Because the distractor was usually clearly distinct from the target, it is concluded that physical separation is not a sufficient condition for selective perception; overloading perception is also required. This allows a compromise between early and late selection views and resolves apparent discrepancies in previous work.