Directed attention dichotic listening in reading disabled children: a test of four models of maladaptive lateralization.

In two experiments, critical a priori tests compared four competing LD theories of maladaptive language lateralization (Poor Structural Lateralization; Excessive RH Activation; Excessive LH Activation; Excessive LH or RH Activation). In Experiment 1, 32 auditory-linguistic LD children from public schools were compared to 32 high-achieving, age-matched controls. Experiment 2 replicated the main findings of Experiment 1 by comparing 14 LD children to 14 controls attending a private school. The effect of priming or ear order was analyzed in a directed attention, dichotic paradigm with strings of quadruple digit names as stimuli. The order in which the ears were monitored (LE first or RE first) determined (1) in both experiments whether the LD children compared to controls were more weakly or strongly lateralized and (2) in Experiment 2 whether the REA correlated negatively of positively with reading and spelling achievement. The results indicate that the hemispheric processes involved in disengaging and shifting response strategies between dichotic channels may share common neuronal mechanisms with cognitive processes that are important to school achievement. Rather than LD children suffering from a fixed laterality deficit, the results are consistent with the view that a task-dependent attentional dysfunction may interfere with left hemisphere language processes by overengaging either hemisphere. However, pronounced asymmetry in the relative magnitude of the effects at each channel also suggests greater interference in LD children between the systems controlling auditory-linguistic attention and lateral orienting.