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Heidi and her altered auditory feedback device

Mary Kingston, Heidi King | 01.12.2007

Mary Kingston and Heidi King talk about Heidi's much-publicised SpeechEasy device, altered auditory feedback and what this can do for people who stammer.

Heidi King in New YorkLincoln et al (2006) in their review of altered auditory feedback devices over the past 10 years write, "...altered auditory feedback is a collective term for conditions that involve electronically altering the speech signals so speakers perceive their voice differently from normal... masking auditory feedback (MAF), delayed auditory feedback (DAF) and frequency altered feedback (FAF) are the forms of speech alteration typically used to alter the speech signal."

Heidi's SpeechEasy device - a miniaturised in-the-ear device, invisible to the observer and worn monaurally - uses DAF and FAF and she describes the effect as having 'a little man in my ear' while talking.

How AAF works is still unknown though there are many theories. SpeechEasy publicity talks about the device harnessing the well known fluency-inducing effect of choral speech on people who stammer, though this begs the question as to why choral speech enhances fluency anyway?

Another much more useful hypothesis is based on the 'dual premotor model' (Alm, 2006).

Dr Alm's idea is that the brain has two parallel systems for the initiation of speech movements: the medial system consisting of the basal ganglia and the supplementary motor area (SMA), and the lateral system consisting of the lateral premotor cortex and the cerebellum.

In automatic speech we use the medial system, but under certain conditions the brain may shift dominance to the lateral system.

This is activated when speech is linked to sensory input, or when speaking with an increased level of attention in a nonautomatic way, eg when imitating a dialect or playing a role.

He believes people who stammer (PWS) usually only have a problem with the medial system, so that a shift to the lateral system will increase fluency.

Dr Alm writes (personal communication),

"The AAF seems to force the auditory system to work a little harder than normal (showed with brain imaging in Oxford, by Kate Watkins, Steve Davis and Peter Howell). This extra auditory processing may ...shift the dominance towards the lateral system, thereby bypassing the problem of stuttering in the medial system. According to this model the use of fluency skills like prolonged speech has a similar effect, also shifting the dominance from the medial to the lateral system.

 However, the use of fluency skills tends to require quite a lot of attention for monitoring. SpeechEasy might be viewed as an aid which helps the brain to shift from the medial to the lateral premotor system, with fewer demands on attention compared with fluency skills."

So if, as Dr Alm suggests, AAF may be seen as an aid that helps the brain to 'shift track', thus temporarily bypassing the stammering problem, what is it actually like for someone like Heidi to use this device in everyday situations?

Heidi takes up the story

When I first met Mary in May 2005, my stammer was very severe. I struggled with nearly every word, and even parts of words, and I would be fighting for breath by the time I had finished.

My face would become contorted, my shoulders and back very tense, and I would frequently have a headache by the end of the day.

I was exhausted every evening by the effort of pushing out the sounds. But I don't think I was aware then of how unnatural it was to struggle and strain to speak because this was what was normal for me.

I have very supportive parents and as a young child and teenager had received very helpful therapy from the City Lit and the Michael Palin Centre. I have strong beliefs about being accepted as who I am, as a person who stammers, and my rights to access the opportunities society has to offer.

I have a first class honours degree in psychology and when I first came to therapy with Mary I had just completed the first year of my doctorate in clinical psychology.

This had thrown all my ideas about stammering into relief, as more fluency than I was achieving was expected of me.

My therapy with Mary for the first few months was about exploring my attitudes and beliefs using personal construct therapy and trying to decrease the struggle when speaking by using techniques.

During this time I learned a great deal about myself, making more sense of my stammer and its place in my life.

I realised then that some of my beliefs were based on self-defence, but through my therapy and my experiences at that time I was able to strengthen and deepen my convictions and views on the place of PWS in our society.

Mary took me to a lecture at the University of East Anglia by Dr Per Alm and for the first time it became real to me that my stammer, and my difficulties achieving fluency, were not my fault.

At this lecture I also became aware of AAF and decided I would like to investigate this to see whether it could help me speak more easily.

I would like to make it clear though that I have never tried to deny my position as a person who stammers, I just wanted something that would ease the tension of speaking.

My quest became known publicly and I soon found myself being swept along by the media, most particularly by the local BBC who joined me on my trip to New York in June 2006 and filmed me trying out the SpeechEasy device (which I half believed would never work).

It is now nine months since getting the SpeechEasy and I have discovered both its strengths and limitations.

I am far from completely fluent, but the severity of the stammers, and the terrible struggle I used to experience has gone.

The tension, the tiredness and the headaches have all ceased. People listening to me in my media interviews may say I still stammer a lot, but in comparison to how I would have been in these situations I am satisfied.

The situations that were always difficult still are so, but they are much reduced. In less pressured circumstances there is little struggle now and this is a new experience for me.

I have a choice too of when I want more control and when I want to relax, with no pressure to 'perform' fluently.

In addition, I have felt brave enough to challenge myself in situations where I have to rely heavily on my speech, for example giving interviews on television, and joining a Toastmasters speaking group, something I would not have done before. I have even returned to my doctorate from which I had taken a break.

I feel freer talking about the whole issue of stammering and as my face is known locally through the television I am often stopped and asked how I am getting on.

But with all this change Mary's therapy support has been vital for me, in order to explore who I am now that I don't stammer so much.


There are still issues to resolve around the use of AAF, a need for research, and many questions to be answered. For example, what are the long-term effects and will people habituate to it? Who can benefit, what assessment procedures should be used?

We also both feel that therapy before and after getting the device is essential. Some people achieve greater fluency than Heidi, but that isn't the whole story.

The final word, therefore, is Heidi's.

"Long-term effectiveness coupled with therapy is a complex picture and likely to be different for everyone.

"A story of struggle, fluency, talking about stammering, and most importantly a new relationship with my speech, which has allowed me to test and move beyond my boundaries. What lies ahead for me is unknown, but I am filled with excitement and ambition to find out."

Mary Kingston - Principal SLT, specialist in dysfluency
Heidi King - Trainee Clinical Psychologist, University of East Anglia

Alm, P. Stuttering and the basal ganglia circuits: A critical review of possible relations. Journal of Communication Disorders 2004, 37, 325-369.
Alm P. Stuttering and the basal ganglia. Stuttering Foundation of America Newsletter, Winter 2006. Available online:
Lincoln M, Packman A, Onslow M. Altered auditory feedback and the treatment of stuttering: a review. Journal of Fluency Disorders 2006, 3, 71-89.

SpeechEasy is one of many devices available on the market and is, with VoiceAmp, one of the more easily accessible in the UK. See Electronic devices and apps.

Reproduced with permission. This article was published in the November 2007 issue of the Royal College of Speech and Language Therapists 'Bulletin'.