The effects of concentrated and distributed attention on peripheral acuity

Abstract

Two experiments studied the peripheral discriminability of a target differing in its line slope (a tilted T) and in its line arrangement (an L) when presented in briefly flashed displays of upright Ts. The results showed that: (a) an Land a tilted T were equal in discriminability when attention was focused or concentrated on one display position, (b) the discriminability of an L decreased while the discriminability of a tilted T was not statistically significantly affected as the number of display positions that attention needed to be paid to increased, and (c) the reaction time to find a disparate tilted T was less than that to find a disparate L The results are interpreted as supporting the hypothesis that, under distributed attention in peripheral vision, the visual system is more sensitive to differences in line slope than to differences in line arrangement. The results are discussed in connection with hypotheses of how selective attention affects the discrirninab ility of a target.Recently, Beck and Ambler (1972) have reported that a masking flash that controlled the time available to attend selectively to individual letters in a display increased the discr iminab ility of a target differing in its line slopes relative to that of a target differing in its line arrangement. They hypothesized that in peripheral vision differences in line slope are more discriminable than are differences in line arrangement when attention is distributed and not concentrated or focused. This paper presents two experiments designed to compare further the peripheral discriminability of targets differing in their line slopes and in their line arrangements when presented in briefly flashed displays. Experiment I studied how discriminability was affected by prior information regarding the position of a target in a display. Experiment Il investigated the reaction time differences to targets differing in their line slopes and in their line arrangements. Hypotheses of how selective attention affects the discriminability of a target will be considered in the discussion section. EXPERIMENT IThe displays consisted of a circular arrangement of eight letters flashed for 50 msec. An S was given the task of discriminating whether a display contained all upright Ts or a disparate letter _ The disparate letter could be either an L or a tilted T. The lines of an L have the same slopes as the lines of an upright T but differ in their arrangement. The lines of a tilted T have the same arrangement as the lines of an upright T but differ in their slopes. The letters in the display were covered by "This research was supported by National Science Foundation Grant GB-24884. The co mpu ter facilities were made available through ARPA Contract r44620-67C-0099. The paper was written while the first au thor was a visiting member of the Computer Science Center at the University of Maryland. The preparation of the paper was supported in part by National Science Foundation Grant GJ-32258X. 225 masks 50 msec after the offset of the display. A within-Ss design i...

Focused attention in the perception and retrieval of multidimensional stimuli

“…In our previous experiment (Treisman et al, 1977) we found that when a single shape feature (curvature) could mediate discrimination, parallel processing was possible for shapes as well as for colors. However, for shapes which differ only in the arrangement of shared features, the evidence suggests that focal attention is necessary (Beck & Ambler, 1973). The present experiment was also used to throw light on the question of whether shape and color are processed in parallel with each other, using our particular stimuli.…”

On interpreting the effects of location preknowledge: A critique of Duncan

“…One finding that clearly contradicts this prediction is that reported by Beck and Ambler (1973). They found that location preknowledge improved performance substantially for a difficult discrimination (detecting the letter L embedded among Ts) but had no effect on an easy discrimination (detecting a tilted T embedded among upright Ts).…”

Spatial attention: Different mechanisms for central and peripheral temporal precues?

“…On the other hand, the existence of a faster spatial attention system was proposed about a century ago (Helmholtz, 186671911;Wundt, 1902), selecting regions of the visual field for further processing without eye movements. This view has been established by the more recent literature (e.g., Beck & Ambler, 1973;Cohn & Lasley, 1974;Hoffman & Nelson, 1981;Posner, Snyder, & Davidson, 1980;Sperling & Melchner, 1978;Wolford & Morrison, 1980). However, the mechanisms of spatial attention (how spatial attention improves human performance) remain one of the central questions in cognitive psychology.…”