The effects of global and local stimulus context on auditory frequency discrimination

Frequency discrimination thresholds are influenced by various listener, stimulus and task related factors. Here we are interested in the effects of repetitions within the stimulus set used in the discrimination task, and more specifically in the effects of stimulus repetitions within trials (local context) and across trials (global context). In order to examine these aspects, twenty native Hebrew speaking students (10 males and 10 females, aged 20-28), with no known language, hearing, learning or other cognitive or functional problems, performed 4 different auditory frequency discrimination tests differing in the degrees of global and local context they provide. Our findings show that discrimination thresholds were affected by both global and local contexts. In addition, the discrimination thresholds in the condition containing both local and global context were significantly lower than in the condition containing only global context or only local context. There was however no interaction between the two effects. These findings suggest that the effects of local and global context are at least to some extent, distinct, with each making a separate contribution to performance. Furthermore our findings show that the effect of global context was larger than that of local context, which could suggest that each of these effects is related to a separate component of working memory.