Variations in size of the visual field in which targets are presented: An attentional range effect

In Experiment 1, subjects responded with a buttonpress to a target letter O embedded in a pair of vertical lines. A flanker control method was used to constrain the location and size of the initial attentional focus. The target could appear in one of five locations within a particular horizontal range. There were five ranges, varying from 1.7° to 8.6° in visual angle. Reaction time measures to the target exhibited V-shaped curves, with the lowest reaction time corresponding to the location of the initial focus of attention. The slopes of the curves decreased monotonically with target ranges. Reaction time measures at the extreme locations of the five ranges showed no significant increase with eccentricity, indicating that the influence of retinal sensitivity is negligible in this identification task as compared with the influence of other, presumably attentional, processes. Experiment 2 indicated that within a given range the slopes of the reaction time curves are independent of the number of locations probed. Additional evidence for the attentional range effect was given in Experiments 3 and 4, in which the tasks were detection of an asterisk both with and without flanking vertical lines and identification of the letter O with and without flanking lines. These results do not conform to predictions of a shifting focus theory of attention with the velocity of the focus assumed to be constant, or to the predictions of a gradient theory with total processing capacity assumed to be fixed.