Mineka’s work tells a neat story, based around the assumption that snakes and crocodiles were real threats to monkeys and killed them off in huge numbers. Monkeys who were afraid of these animals therefore had a survival advantage. Unfortunately, the evidence does not fully back up the theory. The rhesus monkeys used by Mineka evolved in India, where cobras and other poisonous snakes could have been dangerous. However, there is less evidence that crocodiles would have been a danger. Crocodiles might be feared because of their reptilian similarity to snakes, but this seems rather to weaken the argument.
It partly hangs on how the brain recognises threatening animals or situations. The brain could have a full picture of snake or crocodile irrevocably programmed into its hardwiring. Alternatively, features like smell, sliminess or sudden movements may be what we are on our guard for.
People with phobias often give vivid descriptions of what they fear; the appearance, feel or thought of the animal. Abrupt, jerky, unpredictable movements are frightening. Sliminess disgusts us. Even babies dislike strange, inhuman appearances. Jamie Bennet-Levy and Theresa Marteau in London asked a group of people about rats, cockroaches, butterflies, frogs, rabbits, spiders, blackbirds and other small animals. The volunteers rated each creature for ugliness, sliminess, speed and how suddenly they appear to move. Another group said how afraid they were of the various characteristics and how near they would go to each animal. Not surprisingly, the more harmful the animal was, the more afraid people were and the less prepared to get close. Physical characteristics, especially ugliness, also deterred them. The volunteers in the study said that ugliness was a composition of sliminess, hairiness, colour, dirtiness, number of limbs or antennae, compactness of body and the relation of the eyes to the head. In other words, how different the animals’ appearances were from humans. Touch and sound came into it as well and people hated the thought of a spider running up their leg or in their hair.
Similar work in the Netherlands also concluded that the more animals differ from humans, the more we fear and avoid them. Lack of predictability or control of the animals makes things worse. People are inclined to be suspicious of all things strange and seem ready to fear features of alien species. This suggests that the human brain is set up to notice unpleasant characteristics and probably does not contain a full picture of certain dangerous animals.
It is puzzling, then, that Mineka found monkeys quick to fear toy snakes and crocodiles, which do not have strange smells or movements. Suffice it to say that not even evolutionists can claim that all evidence points the same way.
The inner workings of the brain remain mysterious, despite increasingly sophisticated work such as that described in chapter 4, on neurophysiology. Tracking down the unconscious requires ingenuity and a Swedish group led by Arne Öhman and Joaquim Soares hit upon the idea of using subliminal images. The approach has a certain history. A classic but flawed experiment in the 1950s flashed up a message urging cinema viewers to drink Coca-Cola. The message disappeared so quickly that viewers had no idea their film had been interrupted, but this brief exposure was enough to make them inclined to buy more of the drink. However, the film itself was about food and drink and the results were inconclusive. In any case, sadly for the advertising industry, such tactics remain illegal.
In the laboratory, Öhman and Soares had more freedom and flashed pictures of spiders, snakes, flowers and mushrooms on screen. They recorded skin conductance on volunteers’ hands. It is a measure of arousal in the autonomic system and changes when people have any sort of anxiety reaction. Volunteers responded to the sublimal pictures. For example, people with spider phobias reacted more strongly to pictures of spiders than anyone else. They did not know what they had seen but nevertheless had a physical reaction. Like the cinemagoers who suddenly had an urge to drink cola, the volunteers unconsciously registered the picture they had seen.
The researchers then tried to make the volunteers artificially phobic and gave their finger an unpleasant electric shock as the flashed pictures appeared. Some received the shock when they saw the snake picture, others when they saw the spider, flower or mushroom pictures. They all reacted to the picture paired with the shock.
Volunteers then saw the flashed pictures again but without the shock. Responses to flowers and mushrooms were eliminated but responses to snakes and spiders endured. None of the students had any conscious idea what they were reacting to, but responses to snakes and spiders were consistently more resilient than those to flowers and mushrooms. It implies that the unconscious can somehow pick out fearful stimuli.
By the time we recognise a spider or snake, our unconscious is already generating a rising tide of arousal which puts us on red alert, said Öhman and Soares. This heightened awareness makes us more likely to feel defensive and afraid. Phobics cannot control their fear voluntarily because the initial reaction is unconscious and under the control of deeper, ancient parts of the brain.
These exciting results encouraged the researchers to look at another type of danger: threatening human faces. Threats from predators such as snakes are important to the most primitive creatures and defences would have evolved early. Social threats affect more sophisticated creatures and would have evolved much later. Therefore the relevant information may be processed in the higher brain, the cortex, which carries out more complex functions and developed late in evolution. This ties in neatly with Darwin’s earlier assertion that blushing developed comparatively recently.
The cortex has left and right halves with different functions. If social submissiveness is processed in the cortex, our reaction may depend on where the human face is when we see it. Negative emotion and perception of faces are believed to be processed in the right hemisphere in right-handed people. Information from the left side of someone’s visual field is also processed in the right hemisphere. If someone sees an angry face in their left visual field and the information goes straight to the hemisphere adapted to process it, they may react more vigorously than if the information is sent to the other side of the brain. There are lots of ifs here, but volunteers did react more strongly to a flash picture of an angry face when it was shown to their left rather than right visual field.
If fear of small animals is processed by the oldest parts of the brain, deep down where there is little difference between right and left sides, there ought to be little difference whether the slides are shown to the right or left visual field. This turned out to be true. People’s reactions were similar, regardless of where the slides were flashed up, which supports the idea that this reaction developed early in evolution.
Information on ancient threats is processed first by ancient parts of the brain, according to Öhman. Colour, texture, smell or type of movement may be sufficient to trigger this automatic response and we react immediately and instinctively. We may even have special pathways in the brain for transmitting information about ancient threats, pathways which existed before sophisticated reason and logic and which are physically distinct from those carrying conscious thought. This ancient reaction can produce a groundswell of emotion which colours our thoughts even before the higher brain has engaged and started to make us aware of a potential threat.
Like Seligman, Öhman suggests that responses to ancient threats are easier to establish and harder to extinguish than responses to unnatural or modern cues. It certainly provides a neat explanation for the reactions that may underpin many phobias. The reality is, unfortunately, less straightforward and Öhman’s results have proved fragile. There are many detractors, and even some supporters of the theory have been unable to come up with the same answers.
An American group led by Edwin Cook, himself an advocate of evolution theory, set out to repeat some of Öhman’s work. They used a similar set-up and were surprised to find that reactions to spiders and snakes were as easy to induce as modern fears of guns. It was also equally easy to eliminate them. In direct contrast to Öhman’s predictions, reactions to spiders disappeared as quickly as reactions to guns.
Cook used an unpleasant noise rather than an electric shock, so his volunteers received no tactile stimulus. When he added a vibratory stimulus to the hand, his