Screeeeech!
Question: Why do sounds like scratching a blackboard and scraping metal make some people cringe or shiver? And how does the mind remember sounds? If it can remember sounds accurately why do we not cringe when we remember these sounds?
Answer: The danger warning sounds emitted by some of the great apes are of a similar frequency and tone to the sound made by fingernails dragged on a blackboard, so possibly a primal instinct for danger is being stimulated.
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Howard Vogel
by e-mail, no address supplied
Answer: People do cringe at the memory of sound. Upon reading this question, my back seized up at the thought of fingernails on a blackboard.
Tiffany Caron
by e-mail, no address supplied
Helpless laughter
Question: Why is it that if you tickle yourself it doesn鈥檛 tickle, but if someone else tickles you, you cannot stand it?
Answer: If someone was tickling you and you managed to remain relaxed, it would not affect you at all. Of course, it would be difficult to stay relaxed, because tickling causes tension for most of us, such as feelings of unease due to physical contact, the lack of control and the fear of whether it will tickle or hurt. However, some people are not ticklish鈥攖hose who for some reason do not get tense.
When you try to tickle yourself you are in complete control of the situation. There is no need to get tense and, therefore, no reaction. You will notice the same effect if you close your eyes, breathe calmly and manage to relax the next time someone tickles you.
The laughter is the result of the mild state of panic you are in. This may be inconsistent with 鈥渟urvival of the fittest鈥� theories, because panic makes you more vulnerable. But as in so many cases, nature is not necessarily logical.
Sigurd Hermansson
Stockholm, Sweden
Little drip
Question: Many people find the sound of a waterfall relaxing and soothing, but they also find the sound of a tap dripping slowly during the dead of night irritating. The latter sound has the capacity to penetrate and invade the deepest sleep. Why is this?
Answer: Humans evolved to be sensitive to noise with a pattern that could betray human (or animal) origin. A cacophony of raindrops or crickets does not indicate a potential threat, but a periodic dripping or chirping cries out for investigation.
Brian Holt
by e-mail, no address supplied
Answer: Parents calm their young by producing a constant monotonic sound (mother cats purr to their kittens, humans sing softly to their children). Mammals feel calm and protected when they hear this type of noise. Hence the sound of waterfalls (or the constant sound of driving on the highway) help you to sleep or relax.
The response to the sound of dripping is also a built-in, instinctive response. When you sleep, there could be predators out there poised to eat you. You need to be ready to fight or flee, even when sleeping. When a sudden sound is heard, your brain thinks there is a problem and wakes you. The sink dripping is a series of sudden noises that says to your body: 鈥淪omething is there that shouldn鈥檛 be. This could be a problem, so check it out.鈥�
Seth Karpel
by e-mail, no address supplied
Answer: One of the most intractable problems in psychological acoustics is that of defining the annoyance caused by sounds that have different acoustic spectra. However, it is clear that impulse noise, which a dripping tap resembles, is far more disturbing than other sounds of equivalent acoustic power. Conversely, 鈥渨hite鈥� noise, which contains all frequencies at the same amplitude (and which a waterfall approximates), is curiously soothing. It can also be used to mask other sounds, so a white noise generator (a simple electronic circuit connected to your stereo) would prevent you from hearing the drip鈥攁lthough it wouldn鈥檛 do anything to conserve water.
C. R. Cavonius
University Institute for Industrial Physiology
Dortmund, Germany
Sweaty cheese
Question: Whenever I eat a piece of Cheddar cheese, a cool, tingling sensation occurs beneath my eyes and over the bridge of my nose. This often results in the release of tiny beads of sweat in the same region. Can anyone explain this phenomenon and why this effect is not triggered by any other type of cheese?
Answer: This is a true sign of an allergic reaction. There must be something unique in the process of making cheddar cheese compared to most other cheeses. If you investigated the differences鈥攁 thicker/thinner cheese cloth made of different material, perhaps, or the addition of a smoky flavour鈥攖hen you may find the answer. Also, you will need to be tested for this allergy.
Mike Martin
by e-mail, no address supplied
Answer: Yellow dye is added to commercial cheddar. If you look at the cheddars in a natural food store you will see that they are not orange like the cheeses in supermarkets. You probably have a mild reaction to the dye.
Laurel Veltman
by e-mail, no address supplied
Catch your death
Question: Is there any connection between being cold and catching a cold? If not, why is there so much folklore about catching a cold if you sleep uncovered or in a draught?
Answer: No, there is no connection. The erroneous association developed for several reasons.
The viruses that cause colds spread faster in the winter because people spend more time inside, where they are closer together.
People close the windows in the winter so air contaminated by virus particles is not diluted by 鈥渇resh鈥� air from the outdoors. This makes it easier for the viruses to spread.
The cold, dry air of winter makes the mucous membranes in the nose swell. This produces the 鈥渞unny nose鈥� we often incorrectly associate with an infection caused by a cold virus.
The experience of a catching a chill and getting a cold is actually the reverse of the correct order of things. The 鈥渃hill鈥� is often the first sign of fever that is the result, not the cause of, the infection by the cold virus.
Mark Feldman
Northland, New Zealand
Answer: Studies have shown that there is no correlation between environmental temperature and suffering from colds. The origin of the old wives鈥� tale that predicts colds, flu or pneumonia after being exposed to cold is the short period of fever that precedes the distinctive symptoms of these illnesses. These periods of fever make the patient feel cold or shivery. Shortly after developing the other symptoms, the patient then associates the illness with having 鈥渃aught鈥� cold. Indeed, the flu is called influenza from the belief that it was caused by the 鈥渋nfluence鈥� of the elements. The fact that isolated researchers living in Antarctica never catch colds confirms that these are caught from people and not from 鈥渃old鈥�.
Pedro Gonzalez-Fernandez
London
Answer: There is actually less chance of your catching a cold in the cold. The virus known as the common cold dies in cold and needs warmth (say the cosy indoors of a home beside the fire started to keep out the cold?) to thrive.
Esperandi
by e-mail, no address supplied