Selective effects of prior motivational experience on current on-line control of attention.

This study examined the influence of prior motivational experience on the efficiency of executive attention control during performance of a task set reconfiguration task (Rogers & Monsell, 1995). Results revealed that motivation manipulations selectively affected attention switching mechanisms, but did not influence either inhibition of crosstalk from competing stimuli, or basic response execution time. This provides additional evidence for distinct attentional systems involved in resolution of response and perceptual competition. Speculations regarding the neural systems that mediate both motivation and attention switching are considered, pointing to a possible involvement of dopaminergic influences on the ventral striatum.

Cerebral hemispheric involvement in the acquisition of new phonetic categories.

This study was concerned with the involvement of the cerebral hemispheres in the acquisition of perceptual skill with novel speech sounds. Two groups of eight subjects rated on three occasions the dissimilarity of pairs of Mandarin Chinese speech sounds varying on voicing and aspiration, presented to the left or right ear with contralateral noise. The experimental group received listening experience with long passages of Mandarin containing the target sounds. Multidimensional scaling analysis of dissimilarity ratings indicated that listening experience leads to increased perceptual differentiation of phonetic categories drawn from a language unfamiliar to the listener. This improvement occurred sooner with presentation of the target sounds to the right hemisphere than to the left if the phonological contrast was along the voicing dimension. Improvement in the perception of stimuli varying on aspiration occurred in right ear presentations only. This finding supports the position that speech perception mechanisms at the feature level may be distributed asymmetrically across the hemispheres.