Speech Processing Deficits In People Who Stutte

Developmental stuttering is a speech fluency disorder in which an individual knows exactly what he or she wants to express during speech,but has difficulty in doing so due to repetition,prolongation,or pauses.Speech production is a complex multi-stage process,including concept preparation,lemma selection,phonological encoding,phonetic encoding and articulation stages.Errors in any of these stages may result in speech disfluency.At present,most theories and studies believe that stutterers have defects in speech processing.However,few studies have differentiated the defects in phonological encoding,phonetic encoding or articulatory motor planning.Different stages of speech production have different processing characteristics.The differentiation of stage abnormalities for stutterers will help stutterers lock the specific stage of processing difficulties.After that,targeted treatment and speech skills training can be adopted for problems existing in different stages,so as to help stutterers to correct more effectively and reduce the occurrence of speech disfluency events.Our research will also help to improve the existing stuttering theoretical model and provide reference for future research on stuttering.Therefore,through three behavioral experiments,this study examines that the speech defects of stutterers specifically occur in one or several stages of phonological encoding,phonetic encoding and articulatory motor planning,so as to provide theoretical basis and practical guidance for the correction of stuttering.In experiment 1,43 participants,including 21 adults who stutter and 22 adults who do not stutter,were selected to use the picture-word interference paradigm combined with the immediately naming task,that is,the participants were required to say the name of the target picture quickly and accurately while seeing the target picture matching the related or unrelated distractor words.The naming of the target picture will be affected by the interference of the related or unrelated distractor words in the center of the picture,which will affect the naming latency of the picture.The results showed that there was a significant syllable facilitation effect in both groups,and the naming latency of target pictures in the syllable-related condition was significantly smaller than that in the syllable-unrelated condition.More importantly,the facilitation effect size was significantly larger in stutterers than in non-stutterers.These results indicate that there are phonological processing defects in speech production.The participants in experiment 2 were the same as those in experiment 1,using the picture-word interference paradigm combined with the delayed naming task,that is,the participants were required not to name the target picture and the distractor word immediately when they saw them,but to name the target picture after the subsequent prompt clue appeared.The naming of the target picture would be interfered by the related or unrelated distractor word presented in the center of the picture and affect the naming latency when naming pictures.The results showed that the facilitation effect was significant in the stuttering group,but not in the non-stuttering group.These results indicate that stutterers have processing defects in the stage of articulatory motor planning.In experiment 3,38 participants were selected,including 18 stuttering participants and 20non-stuttering participants,from the same group as in experiment 1 and experiment 2.The picture-word interference paradigm was used to combine delayed naming and articulation suppression task,that is,the participants were asked not to name the target picture and the distractor word immediately,but to say the name of the target picture after the prompt clue appeared,and the participants were asked to complete the articulation suppression task of repeatedly saying "1" while waiting for the prompt clue to appear.The naming of the target picture will be interfered by the related or unrelated distractor words presented in the center of the picture before,which will affect the naming latency of the picture.It was found that there was no significant facilitation effect in either group.The above results indicated that neither group produced the expected facilitation effect,and it was impossible to compare the differences and similarities between the two groups of participants in the phonetic encoding and articulatory motor planning through experiment 3.By comparing the results of experiment 1 and experiment 2,it can be found that there is an interaction between experiment type and participants type.There is a difference in the facilitation effect between stutterers and non-stutterers.The difference in the facilitation effect size between the two groups in experiment 1 is larger than that in experiment 2.This suggests that in addition to the difference between the two groups caused by the articulatory motor plan in experiment 1,there is also a difference between the stuttering and non-stuttering groups in the stage from phonological encoding to phonetic encoding.Stutterers not only have phonological processing defects in the stage of articulatory motor planning,but also in the process of phonological encoding to phonetic encoding.In this study,we compared the facilitation effect produced by the two groups of participants in the experiment and between the experiment,proving that stutterers have abnormalities in the articulatory motor planning stage,showing abnormal activation of speech initiation.In addition,stutterers also have speech processing defects in the process from phonological encoding to phonetic encoding,especially in the stage of phonological encoding,which is manifested as abnormal activation of speech initiation.