Toward solving the inferential problem in laterality research: Effects of increased reliability on the validity of the dichotic listening right-ear advantage

As noted by Satz, the prevalence of lateralized language in the general pop ulation is underestimated substantially by the proportion of people who sho w the typical asymmetry on a laterality task. In a series of two dichotic l istening experiments with a total of 171 right-handers and 170 left-handers , we tested the hypothesis that increased reliability of measurement will l ead to increased classification accuracy. Experiment 1 showed that neither the frequency nor magnitude of the right-ear advantage (REA) for fused rhym ing words increased as the number of trials increased from 120 to 480. Ear- difference scores were highly reliable (r = .85), even when based on 120 tr ials. Experiment 2, which involved lists of dichotic word pairs, yielded si milar results. Even though retest reliability of the ear-difference score f or 132 word pairs was only .45, neither the incidence nor strength of the R EA increased significantly when the number of pails was increased to 528. T he results indicate that the pool classification accuracy of dichotic liste ning tasks cannot be attributed to unreliability.