An Investigation of Peripheral Localization Errors in Older Adults
In a typical useful field of view (UFOV) paradigm, an observer must correctly identify a center target while simultaneously localizing a peripheral target. Previous research has shown that many older adults have difficulty locating the peripheral target in the UFOV paradigm when compared to younger adults (Sekuler & Ball, 1986; Scialfa, Kline, & Lyman, 1987; Ball, Beard, Roenker, Miller, & Griggs, 1988; Ball, Roenker, & Bruni, 1990; Scialfa, Thomas, & Joffe, 1994). However, the reason for this difficulty is not clearly understood. The purpose of this study was to test two potential explanations for the difficulty that some older adults have in locating the peripheral target in the UFOV paradigm. The first explanation was based upon research using the gap paradigm (Fischer & Ramsperger, 1984; Mayfrank, Mobashery, Kimmig, & Fischer, 1986; Fischer, 1987; Fischer & Breitmeyer, 1987). This research has shown that a temporal gap between the offset of a fixation point and the onset of a peripheral stimulus helps to facilitate the disengagement of focal attention. This explanation of peripheral localization difficulties in older adults posited that some older adults have a slowing in the ability to disengage attention from the center target in the UFOV paradigm. Three hypotheses were tested based on this explanation. The second explanation was based upon the assumption that the inability of some older adults to locate the peripheral target in the UFOV paradigm is due to a slowing in parallel processing of the entire display, and posited that peripheral localization is highest when the peripheral target is presented for longer durations. Three hypotheses were also tested based on this explanation. In the present study, thirty-six older adults (age 60 or greater) were tested in a screening phase and testing phase. The screening phase permitted a determination of threshold in each of three subtests similar to those used by Ball and colleagues (Ball et al., 1988; Ball et al., 1990; Ball & Owsley, 1992) in their UFOV task. The threshold was designated as the fastest duration in each of the subtests where subjects could perform the task with 75% accuracy. The testing phase used four testing conditions where the center and peripheral target were manipulated in order to investigate the two potential explanations of peripheral localization difficulties in some older adults. The present study did not clearly support nor reject either of the explanations that were posited. The data did not demonstrate that some older adults are slower at disengaging attention from the center target because the conditions used to enhance disengagement yielded the lowest number of correct peripheral localizations. In addition, the data did not demonstrate that some older adults are slower at parallel processing of the entire display because the length of display time for peripheral targets did not systematically effect localization performance. Based on these findings, it is possible that a slowing in the disengagement of attention or a slowing in the parallel processing of the entire display remain potential explanations for the inability of some older adults to locate the peripheral target in the UFOV paradigm.