David F. Pick
Purdue University Calumet
Robert W. Proctor
Understanding the conditions in which the elderly are able to ignore irrelevant information is of both theoretical and practical importance (e.g., Plude & Hoyer, 1985). The theoretical value of such knowledge is to clarify basic processes of selective attention and how these processes change with age. The practical value is to improve the way in which information is presented to elderly persons.
Most studies of the ability of the elderly to ignore irrelevant information report a deficit. Rabbitt ( 1965) used a task in which subjects sorted cards into two stacks according to whether the letter A or B was present. The location of the target letter varied unpredictably from one card to the next, and the number of irrelevant letters on each card in the pack being sorted varied from zero to eight. The older adults were slower than the younger adults, with this difference increasing as the number of irrelevant letters increased. Comalli, Wapner, and Werner ( 1962) used the Stroop color-naming task to evaluate the interference effects produced by irrelevant information as a function of age. They used three cards each containing 100 items. The first card had the words red, green, and blue, which were to be read as quickly as possible. The second card had the three colors in patches that approximated the size of a word, and these colors were to be named as quickly as possible. The third card was a traditional Stroop card with the three-color words printed in noncorresponding colors of ink, with subjects required to name the ink colors. An Age x Card interaction was obtained, with the older subjects performing significantly worse than younger subjects only on the Stroop card. Other studies using the version of the Stroop color naming task in which RTs to individual stimuli are recorded have confirmed that older subjects show particularly large Stroop effects ( Dulaney & Rogers, 1994; Spieler, Balota, & Faust, 1996).
Using an entirely different methodology, McDowd and Filion ( 1992) evaluated the effects of an irrelevant tone on the GSR response of young and old subjects. They presented tones at various times during an interesting radio program. Two types of instruction were given: Ignore the tones and concentrate on the program, or count the tones and ignore the program as much as possible. The GSR response of the younger group of subjects habituated to the tone in six presentations under the instructions to ignore it, while they went through all 20 tones before the GSR response disappeared when the tones were to be counted. The older subjects were still responding with large GSRs in both instructional conditions at the end of the 20-tone sequence. Like the results of Rabbitt ( 1965) and Comalli et al. ( 1962), these results were taken as an indication that aging results in a reduced ability to ignore irrelevant information.
An exception to the general finding that irrelevant information is more distracting for older than for younger subjects was reported by Simon and Pouraghabagher ( 1978). Subjects made speeded left or right choice responses to an X or 0 presented visually at a centered location. Simultaneous with the letter, a tone whose location was irrelevant to the correct response was presented to the left or right ear. Both young and old subjects showed a typical correspondence effect for the irrelevant location information (often referred to as the Simon effect): Reaction time (RT) was faster when the location of the tone corresponded with that of the response than when it did not. However, the magnitude of the correspondence effect did not vary as a function of age (young, M = 26 ms; old, M = 23 ms), even though the older subjects' mean RT was more than 100 ms slower than that of the younger subjects.
It is possible that the processing of irrelevant location information is not affected by age. However, the procedure used by Simon and Pouraghabagher ( 1978) differed from that used in most other investigations