The psychological refractory period: evidence for age differences in attentional time-sharing.
The authors report 2 psychological refractory period (PRP) experiments in which the stimulus onset asynchrony (SOA) between Task 1 and Task 2 was 150 ms, 250 ms, 600 ms, and 1,100 ms for both younger and older adults. H. Pashler's (1994a) response-selection bottleneck theory predicts that SOA manipulations should not affect Task 1 performance, but that reaction time (RT) for Task 2 should increase as the SOA between the 2 tasks decreases (i.e., the classical PRP effect). In Experiment 1 (Task 1 = tone discrimination, Task 2 = dot location), older adults showed a larger PRP effect than younger adults did, although Task 1 RT was affected by SOA, suggesting that participants were grouping their responses on some trials. That is, participants were holding their response for Task 1 until they had completed processing Task 2, and then they responded to both tasks almost simultaneously. However, a subset of participants (11 younger adults and 11 older adults) who showed no evidence of response grouping on Task 1 continued to show a larger PRP effect for older adults on Task 2. In Experiment 2 (Task 1 = dot location, Task 2 = simultaneous letter matching), older adults continued to show a larger PRP effect than younger adults for Task 2, and Task 1 performance was unaffected by SOA. Consequently, these experiments provide evidence that older adults (relative to younger adults) exhibit a decrement in time-sharing at the response-selection stage of processing. These results suggest that attentional time-sharing needs to be added to the list of topics examined in aging research on varieties of attention.
Allen
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Department of Psychology, Cleveland State University, Ohio 44115, USA. r0500@vmcms.csuohio.edu
Smith
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Vires-Collins
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H
Sperry
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S
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D003430:Cross-Sectional Studies; D006801:Humans; D008875:Middle Aged; D010897:Pitch Discrimination / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D013997:Time Factors; D014836:Volition / Q000502:physiology