Monday, July 10, 2006

Auditory system: cause or necessary condition only?

I have spoken about the findings of several research articles that claim an abnormality (in activation or anatomy) in the auditory system, and its consequences: see here. I said that it dont believe that "bad hearing" is causing stuttering.

While cycling up a long hill (trying to imitate the Tour de France), I suddenly came up with a way that might explain lower activation in auditory regions. Here is the line of arguments:
1) People with PDS at birth have no different hearing capabilities (or potential for) than the average population.
2) Learning to speak effectively involves fine-tuning your neural networks to produce speech, and this is only possible with feedback from your auditory system. You need to hear to be able to fine-tune your speaking networks. That's why deaf kids cannot learn to speak properly (except if they get a Cochlane implant).
3) Some kids have a better auditory system than others, but they all manage to learn to speak.
4) Now, I assume that dysfluent kids have an inherent weakness / abnormality (genetics or neurological incident), and the fine-tuning becomes more difficult.
5) Only the kids that have abnormally good hearing are able to do the fine-tuning and recover. The kids with average and lower activation do not, even though had they not had the weakness / abnormality they would have.
6) So looking at dysfluent kids you will find average hearing capabilities (thinking everything is fine). But in adults with PDS you will see an on average lower activation of auditory system.
7) One can even argue that only a temporary delay in the development of the auditory system around age 3-5 will hinder fine-tuning. So you wont see a statistical signal either for all dysfluent kids or for stuttering kids after age 5.

This is only brainstorming. But this scenario shows well that something might not be a cause of stuttering (the weakness / abnormality is), but a necessary condition for it to happen.


Anonymous said...

Hi Tom,

I appriciate your blogs very well. Thanks for that. Regarding you brainstorm about stuttering and hearing I missed a point of view.

A project of Prof. Dr. F Wijnen is regarding stuttering and monitoring.
In my opinion is monitoring a different issue then hearing.

One of the exercises during his project was "speaking without a voice". In such case there is no influence of hearing. Becasue the persons did not make any noise.



Tom Weidig said...


I'll have a look at it.