Dichotic abilities in children, normal adults and aphasic adults for open- and closed-context words.

Abstract

School children (N: 147, distributed across grades from K through 5), 15 normal adults aged 19-30 yrs, and 11 aphasic adults with stabilized aphasia either of traumatic (N: 5) or cerebrovascular (N: 6) origin were used to explore the non-acoustic element of cognition as an influence on dichotic behavior. All Ss were audiometrically normal. Dichotic performances were assessed across age and condition. Pairs of words from the Peabody Picture Vocabulary Test (open-context) and common color names (closed-context) were presented simultaneously to both ears at about 70 db SPL by stereo tapes and earphones. Each pair was adjusted to +/- 3 msec for time-of-onset and +/- 4 db in level. S reported words heard. Performance was assessed for single- and for double-correct responses and for order-of-report (L-first, R-first) bias. Consistent with earlier findings, children showed R-ear-advantage in the single-correct and order-of-report measures for both stimulus sets. Double-correct scores were considerably and significantly higher for all Ss for the closed-context words. The older children (Grade 5) performed at adult levels on the double-correct measure for closed-context words, but not on any measure for the open-context words. The children's order-of-report biases were nearly identical to the normal adults'. As expected, the aphasic subgroups performed poorer than any normal subgroups, except K, and those of traumatic etiology yielded responses generally poorer than those of cerebrovascular origin. From the stabilized aphasic patient data we conclude that the R hemisphere appears to have a compensatory capacity for language acquisition subsequent to L hemisphere damage, and that dichotic testing is sensitive not only in aphasia generally, but can distinguish between certain aphasiogenic categories.