Shifting of attentional focus within and about a visual display

Abstract

If several positions must be attended in a large visual display, does the efficiency of performance vary as a function of the display distance between these to-be-attended positions? Two previous experiments (Podgorny & Shepard, 1983;Shaw, 1978) gave conflicting answers. In the present experiments, eight-letter circular displays were briefly presented. On each trial one, two, or three positions of the display were cued or preeued. The number of noncued display positions intervening between the cued locations varied from zero to three. The subjects' task was to rapidly discriminate between two target letters. Although reaction time was found to increase with increases in the number of cued locations, no significant or suggestive effects were found for the spacing or distance between the cued locations. The evidence strongly suggests that the subjeets serially searched the cued locations, which further implies that attention can index locations in the visual field at a speed that is independent of the distance between these locations.If a subset of stimuli must be attended in a complex large visual display, does it matter which way this subset is distributed throughout the display and intermixed with distractor stimuli? Our purpose in the present experiments was to obtain some evidence on this question and to relate the findings to several current conceptions of visual attention. To preclude the role of saccadic eye movements, we dealt only with displays presented for durations too brief for changes in eye fixation.Although there is a vast literature on visual search, only a few studies have addressed the question we have posed above. Two of these studies came up with conflicting answers (Podgomy & Shepard, 1983;Shaw, 1978;Shaw & Shaw, 1977). The visual display used in Podgomy and Shepard's (1983) experiment was a 3x3 matrix of squares. Prior to a trial, a subject was instructed to distribute his/her attention over a subset of these squares. The squares to be attended were lightly shaded. When the subject felt that his/her attention was deployed over the lightly shaded area, he/she initiated the trial. At this point a dot appeared in one of the nine squares. The subject made a discriminated response as to whether the dot occurred on a shaded or a nonshaded square, and the latency of the response was recorded. Latencies were shortest when the target fell on attended squares. Furthermore, the latencies were reduced when the subregion of shaded squares (attended) constituted a compact region on the nine-square display. Latencies increased as attended squares were distributed over the display with nonattended squares intervening between attended ones. Crassini (1986), in a reanalysis of Podgomy and Shepard's (1983) data, concluded that a benefit in responding occurred only when the attended squares were unitary, that is, when the attended squares were not separated or interlarded with squares that were not to be attended (see Shepard & Podgomy, 1986).The results of these experiments suggest that attention can be dis...

Distance and distraction effects in the apprehension of spatial relations.

“…However, the distance effects may have to do with processes involved in screening out the distractors rather than the processes involved in computing the relation between the targets. Eriksen and Webb (1989) cued two positions in a multielement display in a task that did not require computing spatial relations between the cued positions and found that RT decreased as the distance between the cues increased. Perhaps it is easier to ignore distractors if several of them can be grouped together (Duncan & Humphreys, 1989;Humphreys & Miiller, 1993).…”

“…If attention could be focused so that only two objects impinge on the model at one time, then above and below could be assigned unambiguously. However, it is not clear whether attention can be directed simultaneously to two different locations; the issue is currently controversial (see, e.g., Castillo & Umilta, 1992;Eriksen & St. James, 1986;Eriksen & Webb, 1989;Eriksen & Yeh, 1985;Posner, 1980;Shaw, 1978). The evidence that attention can be split comes mostly from experiments that cue the locations of single items (e.g., Castillo & Umilta, 1992).…”

“…The evidence that attention can be split comes mostly from experiments that cue the locations of single items (e.g., Castillo & Umilta, 1992). Experiments that present several items simultaneously often suggest that attention cannot be split (e.g., Eriksen & St. James, 1986;Eriksen & Webb, 1989;Eriksen & Yeh, 1985). Unfortunately, displays of several items are the ones that cause ambiguity and confusion in the Hummel and Biederman (1992) theory.…”

Attentional distribution in the visual field duringsame-different judgments as assessed by response competition

“…However, a reanalysis of their experiments and data (C. W. fails to support such a conclusion. Furthermore, subsequent research has strongly indicated that attention either shifts or indexes locations in the visual field in a discrete manner with the time required for shifts from one location to another to be independent of the distance between the locations (C. W. Eriksen & Webb, 1989;KWak, Dagenbach, & Egeth, 1991;Sagi & Julesz, 1985).…”

Measuring and modeling the trajectory of visual spatial attention.

“…Attempts to characterize attention shifts have used five basic paradigms, all of which involve spatial cues: (a) simple reaction times (RTs; e.g., Hughes & Zimba, 1985, 1987Posner et al, 1978;Posner et al, 1980;Remington & Pierce, 1984;Rizzolatti, Riggio, Dascola, & Umilta, 1987;Shulman, Remington, & McLean, 1979;Shulman, Wilson, & Sheehy, 1985), (b) choice RTs (e.g., Colegate, Hoffman, & Eriksen, 1973;Egly & Homa, 1991;Eriksen & Hoffman, 1972, 1973, 1974Eriksen & Webb, 1989;Hoffman, 1975;Jonides, 1980Jonides, , 1983Klein, 1994;Musseler, 1994;Podgory & Shepard, 1983;Posner et al, 1980, Experiments 3 and 4;Shaw, 1978;Tsal, 1983), (c) discrimination (e.g., Cheal & Lyon, 1989;Cheal, Lyon, & Gottlob, 1994;LaBerge & Brown, 1986;Lyon, 1990), (d) partial report (e.g., Averbach & Coriell, 1961;Sperling, 1960; also see Coltheart, 1980, for reviews), and (e) attention gating (e.g., Reeves & Sperling, 1986;Sperling & Reeves, 1980;Sperling & Weichselgartner, 1995;Weichselgartner & Sperling, 1987). Major theories of attention shifts-spotlight (e.g., Posner et al, 1980), zoom lens (e.g., Eriksen & Yeh, 1985), gradient (e.g., …”