Do individuals with Down's syndrome possess right hemisphere language dominance?

A dichotic digits task with selective listening and attention-switching instructions, was administered to 10 mentally retarded individuals with Down's Syndrome between the ages of 10 and 37 years. Attention was focused on one ear for 20 trials before switching attention to the opposite ear after a 5-minute interval. A majority displayed a right ear-left hemisphere advantage for correct responses, although this advantage failed to reach significance. Comparison of left and right ear intrusion errors when each ear was attended first showed significantly more intrusions from the unattended right ear. No priming effects were found. The results do not support the hemispheric reversed specialization hypothesis. Rather, it is suggested that while Down's Syndrome individuals do possess an inherent left hemisphere advantage for language, such individuals may suffer from a left hemisphere information processing disorder that can produce functional reversals in dichotic listening.