Concurrent cognitive processing and letter sequence transcription deficits in stutterers

Previous research has indicated that men who stutter transcribe rapidly presented sequences of letters more slowly and less accurately than nonstutterer controls. Experiment 1 demonstrated that the transcription deficit is not limited to task conditions that demand concurrent monitoring and responding. This was evidenced by comparable deficits on a successive response condition that required subjects to write letters after the presentation was complete. The results of Experiment 2 indicated that the deficit is not due to a difficulty by stutterers in parsing streams of stimulus information internally. Their performance did not differentially improve when letters were grouped with brief pauses, nor with experience in transcribing preparsed letter sequences. This experiment also demonstrated that the phenomenon is generalizable to women. In related testing, stutterers were slower than controls in writing internally generated sequences of letters, those of the alphabet forwards and backwards, but not in writing the same two letters, A and B, repetitively nor in the cognitively more demanding task of writing numbers backwards by three's. These results parallel those obtained with finger tapping of same versus unique sequences by stutterers and were interpreted as being consistent with the idea that while stutterers are not generally slower motorically than nonstutterers, they experience difficulty when required to organize and carry out tasks with new multiple response transitions. The two experiments have replicated and extended, under different conditions, the earlier findings of a letter sequence transcription deficit in stutterers, but the nature of the interference still remains to be clarified.