A neurolinguistic disorder

Developing a proposal by Nunes (1994), updated by Sandiway Fong (2021, 2023), the evolution of speech and language was bottlenecked by the slowness of transitions across the synapse in contrast to the extreme sensitivity of both visual and auditory perception. Evolution addressed this bottleneck in two ways, first by the successive reductions in the infinity by recursive Merge, and second by the development of a buffer allowing finite time for the apparatus by these steps. Like the specification of the steps, the buffer is developmentally vulnerable. By the proposal of Nunes (1994), an incorrect specification of the buffer characteristically surfaces in speech as a stammer. Putting this differently, a stammer has a necessary neurolinguistic component. Familial experience and self definition are not enough on their own to fully characterise the disorder.

By the proposal of Nunes (1994) experiential or psychological and physical or observational aspects of stammering can be reconciled by a defect with respect to a buffer, already proposed by other authors.

Such a defect helps to explain five things.

1. Stammers occur in all known human populations at a rate of between one and two percent.
2. In all the vast clinical literature about stammering, the disorder is attested only when language is already well-established, most often in early childhood, sometimes later, but never on first words.
3. Like most disorders of speech and language, stammering affects more boys than girls, and often runs in familie
4. By a series of discoveries in the early 1950s, the fluency of most stammerers is improved by hearing themselves speak over a delay, known as ‘Delayed Auditory Feedback’ or DAF; optimally around a third of a second, just enough for a syllable, in contrast to most normally fluent speakers, who block violently and exhibit a variety of the characteristic manifestations of stammering. This has been tested and confirmed in numerous studies of fluent speakers and stammerers. The scale of the effect varies across individuals. The timing is clearly hard-wired and universal across languages and cultures.
5. There is the equivalent of stammering amongst native users of American Sign Language, albeit at only one tenth of the rate in speakers. (America is the only country with enough native signers and other demographic information to get reliable statistics about a phenomenon which only occurs at a rate of one or two per thousand signers).
6. There is such a thing as what is known as ‘covert stammering’ where the speaker has the characteristic self-awareness of stammering, but without displaying any of the characteristic behaviours such as ‘blocking’.

Updating Nunes (1994), one utility of such a buffer is the process evidenced in language after language, allowing words like who, what, where, to be correctly understood when they are pronounced at the beginning of sentences like “Where do you think they said I might have put the car keys?” and understood at the opposite end after any number of intervening clauses. This does not happen in all languages. But even in languages in which the Wh element seemingly stays put, there is evidence of a shifting which is just not pronounced.

If speech and language have evolved, the buffer is a supportive adaptation, storing a small amount of shifted material until it can be interpreted.

The notion of a buffer, vulnerable to neurolinguistic disruption, is highly compatible with the ‘block modification’ approach to the treatment of stammering, as described by Charles Van Riper (1973), the approach that I follow myself.