How much processing do nonattended stimuli receive? Apparently very little, but...

Abstract

The early versus late selection issue in attention models was examined by means of a new methodology. Through cues or precues, attention was directed to one location of a multistimulus visual display and, while attention was so engaged, the identity of a stimulus located at a different position in the display was changed. By varying the time after display onset before the stimulus was changed, we controlled the preview time that the original stimulus was represented on the retina. Then, using a marker cue, we directed the subject's attention to the location of the changed stimulus. The subject's response was a timed discrimination between two possible target letters. The data of main interest was the effect of preview time upon the subject's latency in identifying the new target that appeared in the changed location. We found that the preview time of the original stimulus, before RT was affected to the new target, depended upon whether the original stimulus was a neutral (noise) letter or whether it was the alternative target. When the original stimulus was a noise letter, RTs to the new target were just as fast as those obtained in the control condition in which the target was present throughout the preview interval and did not change its identity. Significant effects upon RT were obtained at preview times of 83 msec when the original stimulus was one of the targets that changed to the alternative target. Preview times also varied as a function of precuing. Preview times were correspondingly shortened when the first cue occurred 50 msec before display onset, thus providing an extra 50 msec for attention to be directed to the first display location. The results were interpreted in terms of two separate information-processing systems in the human: an automatic system and an attentional system. Even though a stimulus may have been automatically processed, when the attention system is directed to that stimulus, processing starts at the beginning again.Pashler (1984) has presented a series of experiments that call into serious question a basic assumption of lateselection theories of attention, namely, that stimuli are parallel-processed and identified before attentional processing is engaged. In these experiments, Pashler used a modification of the iconic memory paradigm of Averbach and Coriell (1961). In the paradigm, an overload of visual information is presented for a brief duration and then, at various intervals after the display has been terminated, a bar or cue designates a location in the visual field. The subject is asked to report the stimulus that had occupied that location in the display. The now classic result is that accuracy of report decreases rapidly as the cue is delayed with performance, becoming asymptotic at around 300 msec.In his first experiment, Pashler modified the Averbach and Coriell procedure in several ways. He used displays of eight letters presented in two rows of four characters each. Three probe conditions were used. In the early-probe condition, the probe preceded the display by 200...

Is evidence for late selection due to automatic or attentional processing of stimulus identities?

“…Also, response compatibility tasks show that if stimuli at task-irrelevant locations have highly learned stimulus-response correlations that conflict with the target response, the target response is usually delayed (e.g., Colegate, Hoffman, & Eriksen, 1973;Fournier, Bowd, & Herbert, 2000). Results supporting the two systems framework come from research by Eriksen et al (1990). They showed that response to a target could be disrupted if the original letter occupying the target location could activate a highly learned, competing response and change to the target letter before focal attention apparently shifted to this location.…”

“…To accomplish this, the methodology developed by Eriksen et al (1990) was used because it provides a measure of the time course of stimulus identification and can potentially determine whether identification of an object occurs before focal attention is allocated to an object (Shiffrin, Diller, & Cohen, 1995). We describe Eriksen et al's (1990) methods, findings, and conclusions in some detail, since we will be evaluating their conclusions by utilizing their methods.…”

“…The second framework is the two systems framework proposed by Eriksen, Webb, and Fournier (1990). In contrast to the perceptual load framework, this framework assumes that two systems are responsible for identity processing.…”

“…This study determined whether evidence for late selection is due to attention processing or to processing by an automatic system that is separate from attention (two systems framework; Eriksen, Webb, & Fournier, 1990). The task was a two-choice discrimination of a target that appeared in one of two sequentially cued locations in an eight-letter visual display.…”

“…Also, the original letter changed to a target following cue 2 onset at predetermined delays (change delays) ranging from 0 to 83 msec. Eriksen et al (1990) posited that if the original letter was incompatible with the target and was identified before attention shifted from the cue 1 to the cue 2 location, the incompatible letter should interfere with target identification even at short change delays. This is because automatic identification of the incompatible letter should activate its associated response and compete with the alternative, target response (B.…”