Individual differences in auditory electric responses. III. A replication, with observations of individual vs. group...

In the first two reports in this series (Lauter & Loomis, 1986, 1988) we presented data on repeated-measures testing with auditory brainstem responses (ABRs) for a group of 7 normal young adults. In this paper, we report data for an additional group of 8 young adults, which replicate the patterns for both latency and amplitude stability observed in the first group, in spite of a number of procedural differences between the two studies. Examples are also presented from both groups illustrating the effects of individual-subject characteristics on group characteristics. Results indicate that ABR latency-variability patterns based on 8-week series are quite different from subject to subject, including individual peculiarities in the pattern of responses according to ear-of-presentation, and the detail of these differences may both contribute to and be obscured by the group within-subject calculations. In contrast, ABR amplitude-variability patterns are much more similar across individuals and ear-of-presentation, most often taking the form of a 'W-shaped' function, with greater consistency at peaks I, III, and V, compared with peaks II and IV.