Interactions of age, ear, and stimulus complexity on dichotic digit recognition.

The effect that the aging process has on recognition performance was studied using a hierarchy of 1-pair, 2-pair, 3-pair, and 4-pair dichotic digits (1, 2, 3, 4, 5, 6, 8, 9, and 10, male speaker). Two groups of right-handed subjects were studied: 20 adults < 30 years of age with normal hearing and 20 adults 60-75 years with mild-to-moderate hearing loss. Each of the multipaired sets contained the 72 possible 1-pair digit combinations in each presentation position with no digits repeated in a set. A three-way analysis of variance with repeated measures indicated three significant differences. First, as the complexity of the listening task increased from 1 pair to 2 pairs to 3 pairs to 4 pairs, recognition performance decreased systematically and significantly. The decreases in performance between the 1- and 4-paired conditions were larger for the left ear than for the right ear and were larger for the 60-75 years group than for the < 30 years group. Second, performance on the materials presented to the right ear was significantly better than performance on the materials presented to the left ear. Third, recognition performance by the < 30 years group was significantly better than recognition performance by the 60-75 years group. Recognition performance on the 1-pair condition was near maximum for both subject groups. Between the 1- and 4-paired conditions, recognition performance for materials presented to the left and right ears decreased 15.7 percent and 10.0 percent, respectively, in the < 30 years group and decreased 29.3 percent and 15.7 percent, respectively, in the 60-75 years group.