Age-related changes in selective attention and perceptual load during visual search

Abstract

Three visual search experiments were conducted to test the hypothesis that age differences in selective attention vary as a function of perceptual load (E. A. Maylor & N. Lavie, 1998). Under resource-limited conditions (Experiments 1 and 2), the distraction from irrelevant display items generally decreased as display size (perceptual load) increased. This perceptual load effect was similar for younger and older adults, contrary to the findings of Maylor and Lavie. Distraction at low perceptual loads appeared to reflect both general and specific inhibitory mechanisms. Under more data-limited conditions (Experiment 3), an age-related decline in selective attention was evident, but the age difference was not attributable to capacity limitations as predicted by the perceptual load theory.

Figure 1

Examples of the displays (no. of letters) used in Experiments 1 and 2. The participant’s task was to identify which of four target letters (H, C, S, or K) was present in the display. The letters H and C were assigned to one response, and the letters S and K were assigned to the other response. Target location varied from trial to trial. Participants were instructed to ignore the distractor locations (3 and 9 o’clock), even if a target letter was presented there. In each of the sample displays, the target letter is C, but the distractor letter varies by condition. In the incompatible condition, the distractor letter was one of the letters assigned to the opposite response of the target letter (e.g., the target was C, the distractor was S or K). In the compatible condition, the distractor letter was assigned to the same response as the target letter (e.g., the target was C, the distractor was H). In the neutral condition, the distractor was a letter not assigned to a response (the letter R). In the experiments, the displays were presented as white letters against a black background. The sample displays are not scaled to size.

Figure 2

Mean reaction time difference scores (with standard error bars) representing compatibility effects for younger and older adults as a function of relevant display size (no. of letters) for Experiment 1. I-N = incompatible RT minus neutral RT; C-N = compatible RT minus neutral RT.

Figure 3

Mean reaction time difference scores (with standard error bars) representing compatibility effects for younger and older adults as a function of relevant display size (no. of letters) for Experiment 2. I-N = incompatible RT minus neutral RT; C-N = compatible RT minus neutral RT.

Figure 4

Examples of the displays used in Experiment 3. The participant’s task was to identify which of two target letters (X or N) was present in the display. Target location varied across the display positions. The distractor was always presented to the left or to the right of the display. Participants were instructed to ignore the letters presented outside the circle, even if a target letter was presented there. In each of the sample displays, the target letter is N, but the distractor letter varies by condition. In the incompatible condition, the distractor was the letter assigned to the opposite response of the target letter (e.g., the target was N, the distractor was X). In the neutral condition, the distractor was a letter not assigned to a response (the letter T or L). In the experiments, the displays were presented as light gray letters against a black background. The sample displays are not scaled to size.

Figure 5

Mean reaction time difference scores (with standard error bars) representing compatibility effects (incompatible RT-neutral RT) for younger and older adults as a function of relevant display size (no. of letters) in Experiment 3.

Figure 6

Mean reaction time proportion scores (with standard error bars) representing compatibility effects [(incompatible RT-neutral RT)/neutral RT] for younger and older adults as a function of relevant display size (no. of letters) in Experiment 3.