Observations placeholder

Dr Stephen Black – Mind and Body

In 1959 I conceived the idea that it might be possible to produce 'frequency selective deafness' by DSUH [Direct Suggestion under Hypnosis] and that in this way the subject could be made deaf only to a particular aural frequency or range of frequencies: simply put, would become deaf to a particular note. Such work would involve the accurate production of sound of a specific frequency-‘monochromatic sound'-or alternatively sound of a precisely controlled range of audio frequencies. I therefore discussed the matter with Wigan in the Engineering Research Department of the BBC at Kingswood Warren.

Wigan was already well known in the audio-frequency field for his work on the Muirhead-Wigan decade audio-oscillator as incorporated in many pieces of test equipment in communications engineering. He immediately declared his interest in what he described as 'the cocktail party phenomenon'. As Wigan proposed it, hearing is a sense with only a slightly 'directional' quality-as rendered by the effect of having two ears. In this respect it differs greatly from vision. How then at a cocktail party where the noise level is so high and the 'message-noise ratio' so low, do we manage to 'project our hearing' and catch, if we want to, exactly what the pretty girl in the far corner is saying to the objectionable young man?

For this in fact is what we are all able to do.

More significantly, Wigan pointed out, that whatever our powers of 'hearing projection' in this way, if we ourselves are talking to the pretty girl there is no difficulty at all in hearing what she says, whatever the ambient noise level as produced by the rest of the party. This suggested in particular that some kind of selective deafness must be going on.

But the 'cocktail party phenomenon' was in no way frequency selective and there was little previous work to indicate that deafness to a specific frequency could be produced by DSUH.

Erickson (1938) had elicited various degrees of total deafness by DSUH and some of his subjects claimed afterwards to have had a subjective experience of selective deafness-not frequency selective-or were said to have relieved their anxiety because of the nature of the experiment by the retention of the hearing of a single sound, such as the ticking of a clock…………..

Wigan and I were not concerned with any of the manifestations of clinical deafness as defined in terms of an accepted norm of auditory acuity according to British or American standards as laid down by the 'ENT boys'. We were only interested in the investigation of possible temporary changes produced by DSUH-and a long series of statistically significant experiments was therefore unnecessary. In our experiments audiograms were simply made of the auditory thresholds of six deep-trance subjects, first awake and again under hypnosis after selective deafness to tone of a very specific frequency had been suggested.

In our experiments the subject lay on a couch and wore high-fidelity head phones fitted with soft rubber pads to keep out the ambient noise of the laboratory. By means of an audiometer the thresholds of hearing were then measured between 100 and 10,000 cps. Since in this procedure the subject must 'say' when the threshold has been reached, the experimental result is still essentially no more than 'the report of a subjective experience'. In our experiments we used two methods, both of which was designed to minimise this subjective element.

In the first method tones of precisely known pitch were produced by using a pulse generator and Wigan's decade audio-oscillator and by means of a variable octave filter any distortion of sound due to the oscillator was kept to less than 0.1 per cent. Various tones between 100 and 10,000 cps were then presented randomly in groups of one, two or three pulses: and the subject flashed a signal light in accordance with the number of pulses heard. Taking the maximum loudness available as plus 100 dB, the tone at each frequency was lowered until either there was no response at all from the subject, or the signal-flashes given could no longer be correlated with the pulses. This point of dB loss was then taken as the threshold of hearing for that particular frequency.

In the second method we used a Bekesy audiometer which provides an automatic 'gliding tone', the frequency rising steadily throughout the test at the rate of about half an octave per minute.

By means of a spring switch the subject could either decrease the loudness of tone when the switch was depressed, or let the loudness increase automatically by not pressing the switch. The subject was instructed to keep the loudness at a point where the sound could just be heard and the result was automatically recorded on paper.

After making the preliminary record of the subject's normal hearing threshold, hypnosis was induced and the specific frequency involved was presented for three seconds as interrupted tone in the head-phones-for purposes of identification only. DSUH was then given that during the presentation of this tone in the course of a count down from twenty, the subject would become deaf to the tone and nothing else.

Records were taken of the actual words used and at the outset the words "you, will not hear this note" or "you will not hear this sound" were arbitrarily employed. The count down from 20 to 1 was then made during the presentation of the test tone over 20 seconds at a relative loudness of 80 DB. The auditory thresholds of the subjects were then measured by one or other, or both of the two methods available.

When deafness to tone of 575 cps had been suggested, the dip in the audiogram at 575 cps showed that the resulting deafness to this frequency was highly specific. When the Bekesy record was taken when deafness to tone of 500 cps had been suggested, although the precision of the record was not so great, in many respects the subjective element in the experimental design was less in evidence -and the result was no less impressive.

Quite clearly deafness to tone of a specific frequency could be induced by DSUH-and this was found to be the case in all six subjects. But in some subjects this inhibition of hearing tended to decay after periods varying from 10 to 15 minutes, but in others it remained until the suggestions were cleared.

On examination of the subjects when deaf in this way, no response to startle situations created with tone at the test frequency (F.) was elicited-and there was no evidence of voice raising when the subjects talked normally during the presence of this tone at maximum loudness in the earphones. Indeed, with the tone at maximum loudness it was possible to hear it quite clearly when talking to the subject-in spite of the rubber ear pads-and Wigan and I both had difficulty in not raising our own voices.

Particularly interesting was the finding that peripheral vibratory sense at the test frequency, or frequencies near it, was also absent.

This is the sense which the doctor tests when he puts a tuning fork on the ankle bone and the information concerning vibration is known to be recorded and transmitted to the brain by special sense organs and nerve tracts. In some respects we had therefore created an example of symptom conversion: the symptom of deafness had 'spilled over', as it were, into the sensory modality of vibration sense in the rest of the body.

This was not quite so dramatic as a conversion from ulcer to asthma, but it was nevertheless a conversion as a patient might complain: "I'm not only a bit deaf now, but I also can't feel some kinds of vibration."……..

It then became clear that in certain subjects the selective deafness could sometimes include not only this test frequency, but also half this frequency, occasionally twice the frequency and in the case of one subject, a third of the frequency.

Examination of the records used in the course of making the suggestions of deafness then indicated that these discrepancies might be due to inadvertent variations in the words employed to describe the tone. For there appeared to be a distinction between the effect of the words 'you will not hear this note' and 'you will not hear this sound'.

This was investigated further and although in fresh tests all subjects became deaf whatever the words used, in 5 subjects out of 6 there was a predominance of deafness to the tone alone when this was described as a 'note'. When, however, the tone was described as a 'sound', there was a tendency to include [other frequencies]. But in one subject out of the six, a Welsh medical student with a very good ear for music and a fine singing voice, this distinction between 'note' and 'sound' was precisely reversed: so that when the word 'sound' was used he became deaf only to the test frequency, but the word 'note' produced multiple frequency selective deafness.

Without letting the subjects in on the problem, I questioned them at some length while awake as to any distinction they might make between the words 'note' and 'sound'. But although the matter was intelligently discussed by some in terms of music and with reference to 'tune' and 'harmony', none of the subjects provided an answer which could explain the observation. For it had to be accepted that the tone presented was exceptionally 'pure' and without harmonies- and in any case it was difficult to see how sub-harmonics could be produced either by the headphones or in the vibratory mechanisms of the middle ear, even if the first harmonic  might be evoked in this way.

This was, however, one of those situations where the elegance of hypnosis as a research tool becomes most apparent. For unlike the minority of experimental subjects in physiology, my subjects could be questioned under hypnosis and in direct contact with the unconscious mind which was the cause of the experimental results.

Under hypnosis subjects giving predominantly an inhibition of hearing at Fo to the word 'note' said, in effect, that to them the word 'note' had a musical connotation associated with the 'notes on a piano' and that it therefore included nothing but the single tone presented in the head phones. But the Welsh medical student said:

"A note is what you hear in music and in music I always expect to hear harmonies whenever I heard a note. . . . I've never heard middle C on the piano without hearing it reflected in at least the C above and the C below."

Thus given some understanding and appreciation of music, the semantics of the hypnotic instruction took on a wider meaning and the discrepancy between this one subject and the other five-none of whom, it turned out, was musical in any sophisticated sense- was simply a matter of the depth of the aural experience generally.

The implications of this were far reaching and apart from the dangers of using hypnotic suggestion in midwifery already noted- because the suggestion, 'There will be no pain' may mean 'no baby' either-it also implied firstly that in the treatment of psychosomatic illness by DSUH semantics might play a very important role. But secondly it also implied that such semantics might be involved in the production of illness. Moreover, it still left open the possibility that in allergy experiments the words 'You will not react' might well produce a local vasoconstriction if such were physiologically possible.