Exploring the nature of stuttering through a behavioral-neuro-modulation intervention program in bilinguals with stuttering.

There was no untreated comparison group. Everyone received both tDCS and the fluency tasks, so the fall in stuttering cannot be credited to either one, or to the combination. Only 16 people took part, eight in each group. A real difference between treating the dominant and the non-dominant language could easily have been missed. Participants varied in how severe their stuttering was, and the randomisation did not balance severity between the two groups. Speech samples were collected only up to the end of the programme, so there is no information on whether any improvement lasted. No formal tool was used to record side effects of the stimulation; participants were simply asked to report discomfort. The intervention is described as lasting three weeks, but the sentence describing the outcome measures refers to a four-week intervention period, so the timeline is not reported consistently.

The paper declares no financial support and no conflicts of interest. Nothing about any funder's role in the design, conduct or writing of the study is reported.

Do not read this as evidence that tDCS or the fluency tasks reduce stuttering. Every participant received both at once, there was no untreated comparison group, and with only 16 people split into two groups of eight, the finding that the language of treatment made no difference may simply reflect too few people to detect one.