Good Questions: The sound of silence

GASTROPODS and hats are among our subjects the week, but first a query sent to our Thursday Silly Questions feature, but re- routed because it is - literally - phenomenally good.

When we silently sing a tune to ourselves, why can't we adjust the volume?

(Francois Landon, Paris)

We asked the psychologist-philosopher Nicholas Humphrey about this and he said it was a very good question, and one that he had never thought about before. According to Dr Humphrey's model of consciousness, sensation and perception are (to put it very simply) constantly involved in a looping process: the sensory organ (eye, skin, ear etc) registers something 'out there', which the mind then attempts to interpret. The sensation (felt by the body) and the perception (created in the mind) are closely related but distinct phenomena. The mind then feeds back the perception to the sensory organ to compare and cross-check with the sensation. So the eye sees a shape, the mind decides it might be a hippopotamus and sends its version of what a hippo should look like back to the retina for comparison with the image sensed. Discrepancies are referred back to the brain and the looping process continues until some conclusion is reached.

The interesting thing, and crucial for the question of volume in silent hums, is what happens physically when the mind sends its version of an imagined hippo back to the eye. There is a growing body of evidence to support the view that thinking about something may stimulate the same areas of the brain as sensing it. Crudely speaking, you cannot imagine a hippo without referring the image back to what your eyes would have seen had a hippo been there.

Here we digress with a case history. In 1928, doctors in Boston were perplexed by a patient complaining of a swishing sound whenever he opened his eyes. When they listened to his scalp with a stethoscope, they heard the swishing too. The man had been born with an abnormally large cluster of blood vessels at the back of his brain near the visual cortex. The result was an audible increase in blood flow whenever he engaged in the activity of looking. Relating this case, Humphrey points out that the visual cortex is stimulated not only by opening one's eyes, but also by imagining the sight of something. 'The Boston patient would presumably have heard 'swish, swish' even if he had just imagined looking at a newspaper (though this was never tested).' He then hypothesises an analogous case of a man with enlarged blood vessels near his auditory cortex rather than visual cortex. While the real- life case could 'hear himself see', the imaginary one would be able to 'hear himself hear'. And if he imagined a swishing sound, he would actually hear a swishing sound.

But would he hear it loud or soft? One can certainly imagine a whisper, or imagine someone shouting, but, as the questioner implies, the volume remains constant. Or, to put it more impressively, we might say there is no phenomenological depth to the imagined sound. The whispering is a stage whisper, and the shouting is shouting from afar. The re-creation of a tune in one's imagination is a re- creation of the perception, not the sensation, of hearing. But now imagine a piece of music with sudden bursts of high volume, or clashes of cymbals (the Dies Irae from Verdi's Requiem works particularly well). As you imagine the sudden loud bits, you will probably find that you react with a slight tensing of muscles and a twitch of the eyes. A gradual crescendo may have the same effect. While you cannot turn the volume up in your mind, you can turn up the symptoms of high volume to recreate the effect.

Source: 'A History of the Mind' by Nicholas Humphrey.

How fast is a snail's pace? The reason I ask is that my wife and I recently completed walking the 80-mile 'Heart of England' long-distance path in short stretches scattered over the course of about five years. Our average speed worked out at 10ft per hour. Did we beat the snail?

(E H B Williams, Alcester, Warks)

Ten feet per hour works out at two inches per minute, which, oddly enough, is identical to the figure given in our Database of Useless Facts and Foibles as the maximum speed of a snail. So if we allow the snail to cover the course in short stretches, stopping the clock while it rests between periods of maximum effort, we have to adjudge the race a dead heat. Whether the snail could stay the five-year course is another matter. The opisthobranch group of gastropod molluscs, which live in the sea, have a lifespan of only one year, which would count them out before the 16-mile mark. Prosobranchs, which may be marine or land dwellers, may live for up to 20 years, though records for longevity are held either by freshwater species, which would not be much use on a long walk, or by desert snails of the United States which spend much of their lives in a semi-dormant state. Another useful thing to know about snails is that they regularly use up and replace their teeth, with the result that a single snail may, throughout its life, have as many as 25,600 teeth.

Principal source: 'Encyclopaedia Britannica'.

Why do we say 'talking through our hat' for talking nonsense? (Geoffrey Langley, Bristol)

The short answer is: No. The earliest reference in the OED is a 1902 quotation including the words 'talk through a hat'. This falls neatly between 'talk through your neck' (1899) and 'talk through the back of your neck' (1904). Partridge's Dictionary of Slang and Unconventional English also mentions the Australian version 'talk through one's braces' (1920) and, spotted in Los Angeles in 1969, 'talk through one's fly-buttons' which it defines as 'to argue from a base of fancy ideas or false claims' or 'to talk cock'.

Talking through one's hat appears also to have been an American invention, dating back to the 1880s and originally meaning to bluster. Leslie Dunkling, in The Guinness Book of Curious Phrases, suggests an allusion to 'the pompous speech of men wearing imposing top hats', but we cannot exclude the possibility that he is talking through his fly-buttons.

(Photograph omitted)