Adult age differences in the attentional capacity demands of letter matching

The attentional demands of letter matching were assessed using a secondary task technique with three adult subject groups. The mean ages were: Group 1 = 19.9 years, Group 2 = 58.7 years, Group 3 = 68.9 years. The primary task was letter matching on the basis of physical identity (PI) or name identity (NI); the secondary task was speeded response to a tone. Relative to baseline (single-task) tone RTs, subjects at all ages responded more slowly in the dual-task condition to tones on name-match trials than on physical-match trials. Also, the proportional difference in tone RT between baseline and dual-task trials was significantly larger for Group 3 than Group 1, but this analysis did not reveal a larger age difference for NI than PI matching. However, a second analysis revealed that absolute differences in tone RT between baseline and dual-task trials increased with age, and the magnitude of this effect was larger for NI than PI matching. The implications of the findings for theories of age differences in attentional capacity, and for issues in the measurement of attentional demands, are discussed.