On the sufficiency and redundancy of pitch for TRP projection

In two Reaction Times (RT) experiments, subjects were asked to respond with minimal responses to prerecorded dialogs and impoverished versions of these dialogs, containing either only intonation and pause information, hummed stimuli, or no periodic component at all, whispered stimuli. For the hummed, stimuli, response delays and, especially, variances were higher than the original recordings. Responses to mid-frequency pitch utterance-ends were significantly longer than responses to low pitch utterance-ends, suggesting that our subjects fell back to reacting to pauses when presented with hummed utterances ending in a mid-frequency tone. This suggests that, in contrast to low or high end-tones, intonation contours that end in a mid-frequency tone might not contain any useful information for predicting endof-utterance Turn Relevant Places (TRPs). We conclude that just the intonation and pauses of a conversation contain sufficient information for projection of TRPs. However this information is measurably impoverished with respect to original to an extent that increases the “processing” time by 10%. No difference was found between whispered and original speech. This lack of any effect of removing all periodic sound components from the speech signal indicates that in natural speech the pitch signal itself might be redundant for predicting TRPs.