Attention to pure tones

Listeners were required to detect increments of intensity or frequency in trains of pure tone bursts under different conditions of attention. The data were analysed taking into account contralateral events when more than one stimulus train was present. Marked changes in d' and β were found and the changes were positively correlated.

If targets are rare and attention is divided the values of β and d' are the same as in undivided attention provided that the contralateral event is a correct rejection, but fall if the contralateral events are hits or false alarms. If targets and non-targets are equi-probable no such difference is found. The data suggest that the observers can make use of the statistical properties of the stimulus sources. The results are compared with those in recent experiments using pure tones in a discrete trial paradigm and in experiments using semantic stimuli.