Recalling vowel sequences in completing backgrounds: Effects of rhythmic regularity and tempo

Abstract

Previous studies have demonstrated that the rhythmic regularities embedded in naturally produced speech are essential for speech understanding in the presence of competing backgrounds. In the current study, the facilitative effect of rhythmic regularity was further investigated using a vowel-recall task. Listeners recalled the last three vowels from a sequence of 9 to 18 synthetic vowels presented at an average rate of 2 vowels/second along with a competing sequence of harmonic complexes. Through this task, the rhythmic regularity (isochronous or anisochronous) and tempo of the target and competitor sequences as well as the duration of exposure to target rhythmic context (i.e., the target sequence length) were independently manipulated without affecting the intelligibility of individual target vowels. Better recall performance was found for isochronous target sequences compared to anisochronous target sequences and with longer exposure to the rhythmic context prior to recall. The rhythmic regularity of the competing signal had no significant effect on recall performance; however, the tempo of the competing signal was significant with recall performance improving as the background tempo increased from 1 to 4 vowels/second. These effects of rhythm and tempo are consistent with theories of selective listening based on attentional entrainment.