Читать книгу Emotional Rollercoaster: A Journey Through the Science of Feelings - Claudia Hammond - Страница 23

In humans, at least, we do understand something of the chemical constituents of tears. They were first analysed back in 1791 and were found to consist of salt, mucus and water. Most of the watery part comes from the lachrymal glands which are at the top outer edge of each eye. This liquid is sandwiched between inner and outer layers which come from glands with such wonderful names as Zeis, Moll, Manz and the crypts of Henle. The oily top layer stops the liquid from evaporating too fast. When we blink tears slide across the surface of the eye towards the inner corner, but if we cry the tears collect in triangular lakes until they overflow, slipping over the edge of the eyelid and down the cheek.

During the first two or three months of life newborn babies don’t shed tears when they cry. Darwin believed that as babies grow older they develop the ability to cry in order to protect the eyeballs when they screw up their faces in distress. He noted that in every culture extreme laughter, yawning and vomiting also brought tears rolling down the cheeks and concluded that the cause must be the same. When the face is screwed up, he reasoned, the blood vessels around the eye become engorged and tears are needed to protect the surface of the eye. He decided to capitalise on his children’s propensity for tears to test his theory, asking them to contract the muscles around their eyes as tightly as possible for as long as they could, believing that this would induce the production of tears. However, none were forthcoming. He did not let this dissuade him from his theory, concluding that his children were simply unable to produce voluntary contractions of sufficient strength. Tears of sorrow must exist to protect the eyes, he contended, because identical tears are shed when a speck of dust is lodged in the eye.

This is where Darwin was wrong and his assumption takes us to the heart of William Frey’s research. As well as devising methods of inducing sadness to make people cry, Frey experimented with substances which would irritate the eye sufficiently to produce tears. Ammonia and tear gas were ruled out for ethical reasons. Instead he gave his volunteers various other substances to inhale including fresh horseradish, but in the end it was the old cliché – onions – which really made them weep. Even in Shakespeare’s time these were the old crying standby. In The Taming of the Shrew a boy who is acting the part of the woman is advised,

And if the boy not have a woman’s gift,

To rain a shower of commanded tears,

An onion will do well for such a shift.

As well as watching over-sentimentalised films, Professor Frey’s brave volunteers had to put their faces over a blender full of freshly chopped onions and inhale deeply with their eyes open for about three minutes. The moment an onion is cut a substance called thiopropanal-S-oxide is released into the air. When it reaches the tear film on the eye there’s a chemical reaction which produces sulphuric acid, so not surprisingly it stings. The only way to stop the reaction is to cover up the eyeball or to stop the substance escaping into the air in the first place. Hence the two successful methods for avoiding streaming eyes are washing the chemical away by peeling onions under water or wearing contact lenses to prevent the vapour reaching the surface of the eye.

When Frey came to analyse the two types of tears he found that tears are not all the same; the emotional tears contained 24% more protein than the irritant tears. The purpose of these proteins in the tears is to fight infection and to control the levels of acidity on the eyeball. This suggests that something special is happening when we shed emotional tears – an expulsion of chemicals perhaps. For this to have any emotional benefit these substances would need to have an association with stress, but as far as we know there isn’t a clear link between stress and these proteins. However, when Frey dissected whole tear glands he did discover the presence of two hormones known to be related to stress – ACTH and leucine-enkephalin. The former is also found in tears themselves. He believes that when we cry we expel toxic substances which are byproducts of the stress we’re experiencing. The idea is that you flush them out through your eyes with the result that you feel slightly better. Indeed he did find that 85% of females and 73% of men reported feeling better after a good cry. Even the existence of the phrase ‘a good cry’ suggests that it’s seen as useful. I saw a TV advert recently for a CD of ‘All-Time Classic Tearjerkers – the most moving tunes for times of reflection’. The very title accepts that sometimes people want to cry and these sad tunes might help them along.

However, attempts to demonstrate the beneficial effects of crying in a laboratory haven’t quite worked. It ought to be simple. Ask people to rate their emotional state, show them a sad film, wait for them to finish crying and then ask them to rate their emotional state again to see whether there’s been an improvement. Unfortunately there’s usually no difference, suggesting that it’s not the expulsion of toxins through tears that makes you feel better. Perhaps you only feel better if those tears encourage someone else to comfort you. There is a big problem, however, with extrapolation from such an artificial situation to real life. When you cry during a sad film you are simply empathising with the characters and imagining yourself in that situation, which is rather different from feeling so helpless in your own life that you cry. Moreover, the situation is inevitably going to affect the way you feel after crying. At home a good cry might lead to a sense of relief, but at work or in a laboratory you might end up feeling awkward or embarrassed.

There is another possibility for the discrepancy between people’s own reports of feeling better after crying and the laboratory experiments. The mind doesn’t assign equal importance to the creation and storage of memories of different events. We all have biases that affect what we remember. It helps us to justify our crying behaviour if we only recall the times it made us feel better.