Using dichotic listening to study bottom-up and top-down processing in children and adults.

The study examined top-down attention modulation of bottom-up processing in children and adults under conditions of varying bottom-up stimulus demands. Voiced and unvoiced consonant-vowel syllables were used in a dichotic-listening situation to manipulate the strength of the bottom-up stimulus-driven right ear advantage when subjects were instructed to focus attention on, and report, either the left or right ear stimulus. We predicted that children would differ from adults in their ability to use attention to modulate a lateralized ear advantage, and particularly when there was a conflict between the direction of the bottom-up ear advantage and the direction of the top-down attention instruction. Thirty children and 30 adults were presented with dichotic presentations of consonant-vowel syllables. The results showed that the voicing manipulation affected the strength of the ear advantage, and that the children performed significantly below the adults when the voicing parameter caused a strong conflict between bottom-up and top down processing. Thus, children seem to lack the cognitive flexibility necessary to modulate a stimulus-driven bottom-up ear advantage, particularly in situations where right ear advantage (REA) is enhanced by the acoustic properties of the stimuli and attentional demands require a left ear shift. It is suggested that varying the stimulus demands in a dichotic-listening situation may be a novel way to study cognitive development.