An eye-marking investigation of anticipated and observed stuttering.

The subjects of this experiment read a list of words and underlined those on which they expected speech difficulty. The matched and non-stutterers were subsequently called upon to read silently a connected passage in which half of these words were present. During this reading, the relation of eye movement to the words read was recorded on film. Frame by frame analysis of the eyes' exact momentary position revealed that the stutterers evidenced significantly more fixations than did the non-stutterers. They also showed significantly more progressive and regressive eye movements. It follows that the overall duration of their eye movements was somewhat shorter. In contrast, the average duration of the stutterers' fixations were significantly longer for those words on which fluency failure had been anticipated and on words on which it was later observed than on those words on which difficulty was not expected and those on which stuttering did not occur. These data suggest that stutterers search among the words to be spoken and sort out those on which they anticipate and on which they have difficulty.