Research project: Top-down processes and auditory processing

This research project has recently been completed and an article is being finalised for publication.

Dichotic Listening: Interaural Intensity Difference and Non-Forced versus Forced Recall
Kah Yee Tan, Nicci Campbell and Ben Linton

Dichotic listening involves simultaneous presentation of different verbal stimulus to each ear and typically yields a right ear advantage (REA), which is consistent with left hemisphere dominance for speech processing. The REA can be modified by bottom-up factor such as stimulus intensity and top-down mechanism by directing attention to specific ear. Studies in this area have mainly been conducted by affiliated researchers in Scandinavia. In the present study, it was of interest to investigate the interaction effects between interaural intensity difference (IID) and attentional control on REA in UK young adults using English voice stimuli. Twenty right-handed participants were tested using consonant-vowel dichotic syllable pairs with different attention instructions (free recall, forced-right and forced-left conditions). Bottom-up stimulus intensity were modulated by presenting the syllables at equal intensity, left louder and left quieter. The results showed a weak, non-statistically significant REA with non-forced equal intensity condition. When IID and attention favoured the right ear, the REA increased while opposite manipulation reduced the REA. There was also significant interaction between bottom-up and top-down processing with IID being the stronger factor. Compared to equal intensity condition, attentional control had a greater effect in conflicting condition of focusing attention to the ear with weaker stimulus intensity.