David Ward, School of Psychology and Clinical Language Sciences, University of Reading, UK
for brevity, all references are given by hyperlinks, leading to the original sources.
The answer to this interesting and recurring question begins with the fundamental issue as to what is, and is not, cluttering. Earlier research implicated executive functioning, whilst more recently some have conceived cluttering as a language based disorder. The International Cluttering Association’s (2018) TPA-CC model reflects a synthesis of a range of thinking on definition, whilst St Louis and Schulte’s lowest common denominator definition is arguably the ‘safest’ (most constrained). Here, cluttering is viewed as a rate-based disorder and language and executive functioning variables are excluded, although they may both appear as concomitants.
Commonalities between stuttering and cluttering include that (even under the LCD definition) difficulties with phonological processing and selective attention. Details as to the heritability of cluttering are lacking so far, but people who clutter (PWC) often report a family history of both stuttering and/or cluttering. In addition, clients may present with both cluttering and stuttering. Superficially, the unexpected pauses sometimes seen in cluttering can sound like stuttering blocks, and even though they can be seen as different entities (with the stuttering blocks reflecting physical interruptions, and the cluttering pauses a more (semi)-random tension-less cessation of speech), differential diagnosis can be complicated. In addition, cluttering, like stuttering seems to be over-represented in some learning disabled populations e.g., Down syndrome, autism spectrum disorder and Tourette syndrome. Again, like stuttering, cluttering typically arises in childhood, but can also result from neurological change later in life [i]. There seem to be similar male/female ratios (around 4:1) in both disorders although one recent report puts the ratio slightly lower in cluttering.
Commonalities between stuttering and cluttering include that (even in the LCD definition) PWC, like PWS may show difficulties with phonological encoding (Bretherton-Furness 2016). Reliable details as to the heritability of cluttering are lacking so far (Drayna, 2011), but clients who clutter often report a family history of both stuttering and/or cluttering. In addition, clients may present with both cluttering and stuttering, although the degree of overlap is wide ranging. Superficially, the short inappropriate pauses seen in cluttering can sound like stuttering blocks, and (even though they can be seen as different entities, with the first representing a physical interruption, and the second a more (semi)-random tension-less cessation of speech), differential diagnosis can be complicated. In addition, cluttering, like stuttering seems to be over-represented in some learning disabled populations e.g., autism spectrum disorder and Tourette syndrome.
However, there are also significant differences which might suggest that these can be seen as different disorders. Aside from speech rate differences, some PWC may sound almost ‘hyperfluent’, and whilst inappropriate pausing can be a feature of cluttering for some, for others the disorder is characterised by a lack of pausing and working on pause insertion can be a focus in intervention. Many PWC (though not all) are less concerned about their speech output than PWS. In contrast to those who stutter, many PWC experience greater problems when relaxed. However, the key may not be relaxation itself, but the attendant factor of lack of speech/language monitoring or self-regulation. Some PWC report that they clutter more when anxious for precisely the same reason, that is, insufficient focus on speech monitoring.
From an aetiological perspective, preliminary evidence suggests that the functional neuroanatomy of PWC is more closely aligned to those with no fluency disorder than those who stutter. Further, PWC may show problems with language organisation which PWS do not, although stuttering (or fear of stuttering) may have a knock-on effect on language usage. Ultimately, clinicians see some clients who clearly meet the criteria for diagnosis under the LCD but who neither report nor show stuttering characteristics, whether covert or overt. As readers will have seen from the links provided, much of the empirical research into cluttering has come from studies with comparatively small participant numbers and where cluttering has been defined in different terms. Until larger scale studies become routine we must be cautious about interpretation.[i] IFA members have full access to this citation and the rest of the Journal of Fluency Disorders. Consider becoming an IFA member today!