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Van Borsel, Dor, and Rondal (2007) examined the speech of seven boys and two young male adults with fragile X syndrome and considered whether their speech was comparable to that reported in the developmental stuttering literature. They listed five criteria which led them to conclude that the speech patterns of speakers with fragile X syndrome differed from those observed in developmental stuttering. The differences noted were: 1) distribution of type of dysfluency; 2) the class of word on which dysfluency occurred; 3) whether word length affected dysfluency; 4) number of times words and phrases were repeated; and 5) whether there were influences of material type on fluency (spontaneous speech, repeated material etc.). They concluded that the speech of speakers with fragile X syndrome differed from developmental stuttering. The comparisons that van Borsel et al. (2007) made between participant groups were not for speakers of comparable ages. Comparisons with groups of corresponding ages support the opposite conclusion, namely the young speakers with fragile X syndrome show patterns similar to developmental stuttering.
van Borsel, Dor, and Rondal (2007) reported analyses of fluency patterns in the speech of nine males with fragile X syndrome. The nine participants were aged between 10 and 22 years, two of whom were young adults (older than 18 years) and the sample had modal ages of 11 and 14 years. They examined a range of material types, and they reported gross speech rate measures for each participant.
Comparison of their results with previously published ones on developmental stuttering, led the authors to conclude that “individuals with fragile X syndrome show a pattern of dysfluency that is not identical to developmental stuttering.” They based this conclusion on five features in the speech patterns where the two types of speakers differed. These were:
They also noted three ways in which the speech of males with fragile X syndrome was affected in a similar way to developmental stuttering. These were the position the dysfluent part takes in: 1) a word; and 2) a sentence; and 3) whether the word started with a consonant or vowel (dysfluency is more likely for both participant groups when a word starts with a consonant).
As has been said, van Borsel et al. rely heavily on literature to make their comparisons. This is alright as long as precautions are taken to ensure the comparison groups are matched on dimensions that could affect dysfluency patterns: Developmental stuttering refers to the form that starts in childhood and which can continue throughout life. The factors that affect incidence and type of dysfluency in developmental stuttering have different influences over ages. van Borsel et al. (2007) often compared across disorders using groups with very different ages. When comparison is made across groups that are similar in age, this leads to the opposite conclusion to that drawn by van Borsel et al. (2007). Namely, as documented below, the participants with fragile X syndrome appear to have a similar pattern of dysfluencies to that seen in developmental stuttering. Each of the five distinguishing features is considered in turn.
There is no clearcut evidence for differences between speakers with fragile X syndrome and developmental stuttering on the five criteria van Borsel et al. discuss. There may be other characteristics of the speech of children with fragile X syndrome that lead the dysfluencies in this group of speakers to be distinct from those seen in developmental stuttering. For instance, the prominent mandible and high-arched palate that van Borsel et al. mention might conceivably lead to certain articulatory gestures being difficult for these children to achieve, that causes a disproportionate number of dysfluencies on speech sounds that are specific to these speakers.
This work was supported by grant 072639 from the Wellcome Address Correspondence to: Peter Howell, Department of Psychology, University College London, Gower Street, London WC1E 6BT, England. Email: firstname.lastname@example.org