Can expectancy explain reaction time ear asymmetries?

Subjects were presented with dichotic pairs of musical and speech sounds randomly intermixed and the task was to press quickly a response button whenever a pre-specified target sound was detected at either ear. Reaction times were faster to right- than to left-ear speech targets; there was also a trend favoring the left ear in detection of musical targets. Since subjects did not know in advance of each trial whether the dichotic pair would consist of music or speech, the significant interaction between stimulus types and ears suggests that an attentional explanation based on expectancy cannot fully explain ear asymmetries.