Aging, Illusory Conjunctions, and Attention

Abstract

Elderly adults do not perform as well as young adults on complex tasks. Elderly adults' poorer performance may be partly due to an age-related increase in the occurrence of illusory conjunctions. To investigate this possibility, this research is designed to examine the relationship between attention and illusory conjunctions in young and old adult performance. Experiment 1 is modeled after Cohen and Ivry (1989; Experiment 3) and requires participants to perform concurrent digit-matching and letter identification tasks. The digit-matching task manipulates the spread of attention, i.e., narrow vs. wide; and the letter identification task provides opportunity for illusory conjunctions, because both a target and non-target letter differing in color and identity appear in the display. The results suggest that selective attention affects the formation of illusory conjunctions in young but not elderly adults. In young adults illusory conjunctions are more likely to be formed within the attentional window. The elderly are just as likely to form illusory conjunctions inside and outside the attentional window.

Because the design of Experiment 1 requires the participants to identify two properties of the target letter simultaneously (i.e., the subject must determine the color and the shape of the target letter) this experiment is a dual property experiment. Since elderly performance often suffers when required to complete simultaneous tasks (Craik, 1977; Hartley, 1992; McDowd & Shaw, 2000), it is possible that an age-difference in the occurrence of illusory conjunctions in Experiment 1 was due to age differences in ability to handle dual task performance. Experiment 2 was used to investigate this possibility. Thus, Experiment 2 consisted of two conditions. In the dual property condition, the participants were required to determine both the color and the identity of the target letter. In the single property condition, the subject only reported the color of the target letter. Experiment 2 demonstrated that the results of Experiment 1 were not due to the dual property nature of Experiment 1. The pattern of illusory conjunctions was similar whether the requirements of the task were to identify one or two properties of the target letter.