Monday, June 2, 2014

Is stammering a conditioned reflex?

Is stammering a conditioned reflex? To try to answer this question, one first needs to know a little about what a reflex is and what conditioning is.

A reflex is part of a type of biological control system. Reflexes can be built-in or learned. It occurs very quickly before thinking. Reflexes have a high survival value, enabling us to take action to avoid potential danger. There are two types of reflexes:

A ‘simple’ reflex is automatic. A person stepping on a sharp object would, in response to a pain stimulus, initiate a reflex action involving the nervous system, resulting in a motor (muscular) response - retracting the foot away from the object. The brain is only aware of the response after it has taken place.

A ‘conditioned’ reflex is one that has been modified in response to experience (learning). A stimulus that produces a simple reflex response becomes linked with another stimulus. For example, a dog may salivate (a reflex action) when it sees its owner remove a tin-opener from a drawer because it has learned to associate that stimulus with the stimulus of being fed. In his most famous experiment, Russian physiologist Ivan Pavlov (1849-1936) experimented with dogs to establish how they learned new behaviour, and taught them to salivate by merely ringing a bell. This is called classical conditioning - the dog is fed after a bell is rung. Done repeatedly, the dog begins to associate the food with the ringing of the bell. After a while the dog salivates as soon as he hears the bell, even though he is given no food. Pavlov thus confirmed that we can learn through linking one concept with another.

Reward and punishment

There is also another form of conditioning called ‘operant conditioning’, where behaviour which is rewarded is strengthened. If you feed a police dog after he has successfully performed a task, e.g. finding illegal substances in suitcases, his abilities are rewarded and strengthened – next time he should perform as well or even better. The opposite is also true when he is punished – if you reprimand him for messing up the furniture, he will tend not to do it again.

How are these principles applicable to stammering?

The principles of classical and operant conditioning are so much part of our behaviour and personalities that it’s easy not to recognise how they impact on us and our speech.

So-called ‘secondary’ stammering behaviours (e.g. excessive blinking or foot stamping) exhibited by some people who stammer (PWS) seem to be obvious examples of operant conditioned behaviour. A person who blinks his eyes excessively in an effort to speak, initially blinked to distract his mind away from the stammer. In the past this trick worked for him and allowed him to speak. The fluent speech after blinking, however, acted as a reward for the blinking. After doing this trick many times the blinking was reinforced and became a strong operant conditioned reflex, i.e. a persistent habit.

Conditioning, however, plays a much bigger role in stammering than just creating secondary stammering. As I see it, stammering develops as follows:

A young child has just learned to speak. The child, however, is one of the 1% of the population with a tension-sensitive speaking system. This tendency or potential of the system to break down under stress is hereditary and genetic. His vocal cords tend to ‘lock’ or 'freeze' when excessive tension is brought to bear on his speaking system. The system has a tension threshold, and when this threshold is exceeded, the vocal cords lock. When not stressed, the child speaks fluently. But some additional kind of  stress could take him over his threshold. This additional tension could be the result of many things; it could be a generally stressful event, such as being admonished by a parent or falling from a tree. It could also be tension brought on by e.g. saying a new sound, or a difficult word, as part of the process of learning language. For a young child, learning the complexities of grammar, new vocabulary and subtle new meanings of words can generate a lot of tension on his immature speaking system, in particular if this tension is combined with an inherited, genetic predisposition to begin stammering.

When suddenly his cords lock and he finds it difficult to speak, he still tries to speak in spite of this. He struggles to say the sound. Eventually the struggle succeeds and he can speak. This success acts as a reward for the struggle. The struggle is called stammering.

The next time the child is under stress, or when he has to say that same sound that caused the initial problem, the same thing happens: the cords lock and make speech more difficult. He responds as before, with struggle behaviour (stammering) until the cords are released and he can speak. This behaviour is reinforced and eventually becomes an operant conditioned reflex. These reflexes quickly strengthen, as the child is very young and thus more susceptible to conditioning. Over the years, the stammering reflexes are strengthened until they are deeply established.

“Linguistic cancer”

Note that the above explanation points to operant conditioning, i.e. stammering is rewarded as a process that releases the cord lock. Classical conditioning, however, based on association also plays an important role, for instance in the spreading of the disorder within the child’s budding vocabulary. The very first sound on which stammering begins may, for example, have been a ‘b’ in ‘bus’. That word then becomes a stammered word associated with stress, or another negative emotion.

In due course, however, all words starting with a b can become affected. The next step in this process, which can be seen as a type of ‘linguistic cancer’, is that the stress linked to all b-words jumps to the p-sound (a sound very similar to the b sound) through association or prediction. In time, the stammer may spread to all sounds pronounced, like the b and p, with a plosive, such as a d and t. And so stammering can spread throughout the vocabulary.

You may ask: if the vocal cords are the problem, why do people also stammer on sounds that are not formed with the vocal cords, like non-vocalised consonants such as s or f? Well, repeating or prolonging such a sound could be a way of attemping to say the sound following the consonant. That following sound is usually a vowel, where you need to vibrate your vulnerable vocal cords.

What about young children who have outgrown it or have been treated successfully?

According to Dr Martin F. Schwartz, children who have outgrown stammering naturally may have intuitively found ways to cope with vocal cord locks. They may have found ways to relax the cords, for instance by exhaling in such a manner that the lock does not occur. Or they may have started to speak slower, thereby preventing localised speech tension from exceeding their ‘stammering threshold’. Or their general stress levels may have decreased so as not to activate the tendency to stammer. Treatment may have had the same results.

So the various repetitions and other struggle behaviours are merely the results of the person’s efforts to speak while hindered by vocal cord locking. Traditional speech therapy has erroneously focused on the struggle behaviour (the stammering itself), instead of seeing it as the last stage of a well-established conditioned reflex. Trying to do something about the reflex itself is of limited value. Far better to try and avoid this 'chain reaction' from being triggered and resulting in stammering. A better approach may be to reduce or avoid general stress (through stress management and gradual stress deconditioning) together with trying to reduce localised vocal-cord tension (through fluency techniques), which triggers stammering reflexes.

In summary: stammering probably consists of a chain reaction, beginning with tension or stress (which is also learned and conditioned), resulting in vocal cord locks, and ending in conditioned reflexes seen as struggle behaviour, a.k.a. stammering.

WHY do the vocal cords react in this way?

According to the latest findings, the basal ganglia in the brain could be the initial culprit. Some experts feel that one of the basal ganglia’s jobs is to coordinate the vocal cords during speech. A transient malfunctioning of the ganglia under stress may result in a lack of vocal cord coordination, manifesting itself as a locking of the cords. Dr Schwartz speculates that a deficiency of acetylcholine, a neurotransmitter, may be the reason why the basal ganglia do not quite function as they should.            

‘Silent’ stammering

It is to be noted that some PWS do manage to unlearn their conditioned stammering reflexes. They are ‘silent’ stammerers (not to be confused with socially covert stammerers)
, who don’t stammer overtly, but still experience vocal cord locks. When such a lock hits them, they hesitate and are unable to speak, but do not repeat or prolong sounds.
                                                            *    *    *   *   *

The role of conditioning in stammering, however, has never really caught on big in speech therapy circles. 
When talking to either therapists or PWS, it becomes apparent that few are sufficiently interested in, or aware of, the role that conditioning may play in stammering, or of the benefits of stress deconditioning procedures.

Partly this is due to the fact that deconditioning in itself, without taking into account the role of the vocal cord lock, has generally failed to bring positive therapy results for adult PWS. For instance, operant reconditioning for PWS (‘punishing’ someone for stammering and/or rewarding fluent speech) has not been successful when treating stuttering adults. Such failures have resulted in conditioning getting a bad name in stammering therapy. At the time, however, people were not aware that the vocal cord lock could be the core of the stammering block.

Another reason for this negative view of conditioning is probably that conditioning as a source of learning has itself had its critics, who argue that it oversimplifies the much more complex phenomenon of learning; that people are more complex than salivating dogs; and that, unlike other animals, we have free will that can override conditioned behaviour.

Conditioning – the elephant in the stammering room?

While these critics may be correct, it cannot be doubted that a lot of human and animal behaviour is governed by the principles of learning and conditioning. People are, in many ways, creatures of habit and products of early childhood. We, as PWS, have a defect carried over from our early years. Ignoring the insights from conditioning theory as a factor in stammering does not help us.

I believe that conditioning is the elephant in the stammering room. In an age of personal choice it is not fashionable to research or discuss things that limit free will, such as conditioning, reflexes and habits. No surprise then that there is little current interest in conditioning theory. Yet stammering can only be fully understood if people know how stress, conditioning, vocal cord locking and, possibly, partly malfunctioning basal ganglia in the brain combine to result in stammering.

(The above article of mine appeared, in a slightly amended form, in the Summer 2013 edition of Speaking Out, the journal of the British Stammering Association.)

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