The Guess Worker

The struggle for survival has made some animals into brilliant detectives. They are excellent at using clues to search for what they want. They know that a splashing noise means water, a rustle in the bushes might signify prey and the buzzing of bees could lead to honey. At the same time there is a lot of irrelevant information out there. These animals have to distinguish the useful information from the irrelevant. How do they do that?

The pursuit of pleasure

The answer is that they use pleasure. Pleasurable clues are the ones worth pursuing. On the other hand information which produces no feeling (that is, neither pleasure nor pain) is ignored. It's easy to see why: if the buzzing of bees is linked to the pleasure of honey in the animal's mind, then the buzzing noise will also be pleasurable. Useful clues are pleasurable because they are associated with the pleasurable things animals want.

The pleasure from clues is not, of course, an end to itself. It's only there to guide animals towards what they want. Pleasure is an end to itself, though, when animals get what they want. The smell of cooking is a pleasurable clue, but a much greater pleasure comes from what we can think of as the aim - eating the food.

Clues and aims

It should be easy to distinguish clues from aims, shouldn't it? Clues are all incidental stimuli from the surroundings. Aims are needs dictated by biology – eating, sex, caring for children and so on. Right? No – not right. Much of what we might consider to be aims are nothing more than clues. To explain what I mean by this, I'm going to look at the pleasures and pains of eating.

Let's suppose that the feeling of hunger is caused by low glucose concentrations.*1 When glucose falls below a critical concentration, sensory receptor in the blood are activated and send impulses to dopaminergic neurons in the brain. That makes dopamine levels fall, which consciousness interprets as hunger. Hunger motivates animals to find food and eat. After food is digested, glucose concentrations in the blood pass above the critical concentration, and the sensory receptors stop sending impulses. Dopamine levels rise and this is interpreted by consciousness as pleasure.

Does this pleasure come from an aim or a clue? Here it obviously comes from an aim. The basic aim of animals is always to get rid of pain. In this case pleasure is felt because the signals causing pain have stopped.

Pleasure for pleasure's sake

What about the other pleasures of eating? Do the pleasures of taste, smell and appearance of food come from aims or clues? None of the stimuli which cause these sensations directly relieve pain. If we always spat out food before swallowing it, we would experience these pleasures – but in the end we would starve to death. So they can't be aims. They are clues of course: taste, smell and appearance indicate whether food is going to be good for us and whether it will satisfy hunger.

Eating, then, is not an aim. Nor by the same token is having sex, caring for children and most of what we enjoy doing. It might seem strange to think of sex being merely a clue but in reality that's probably what it is: its pleasures are there to lead us on the right path towards relieving pain.

"Something here doesn't add up," you might be thinking at this point. "Sometimes we eat when we don't feel hungry, we have sex when we don't feel sex-starved and we usually enjoy looking after children without feeling any pain at all." And you would be right: we do plenty of activities simply for enjoyment and without being aware of any pain. Not only eating, having sex and looking after children but also watching films, doing sports, going on holidays...the list is almost endless. Doesn't pleasure for pleasure's sake make a nonsense of what I have written above?

To explain why it doesn't we need to go back in time and imagine how the brains of the first conscious animals evolved to process information.

Back to the past

The sensation of pain arose for a specific reason: it motivated animals to seek favourable stimuli.*2 At first the only stimuli which animals sought were those that relieved pain and the only pleasure they felt was the relief of pain. In time, though, natural selection must have favoured animals which were receptive to other kinds of stimuli. These other kinds of stimuli were clues.

Let's say that one of the first clues was taste. If an animal had sensory receptors for taste it could identify food without having to ingest it. It could "suck it and see" before either swallowing or alternatively spitting it out.

That, however, didn't necessarily mean that animals had to become conscious of taste. Swallowing and spitting out can be unconscious reflexes. But for some reason they did. Tastes became either pleasurable or painful. Sensory receptors for taste became connected up to dopaminergic neurons. But why did that happen?

It was to help form new concepts. By being pleasurable a taste could become quickly and strongly associated with other stimuli.*3 These other stimuli could also be clues. Or they could be the stimuli which cause hunger.

It looks good, tastes good and by golly...

Taste is a very reliable clue. It is much more reliable than, let's say, appearance. Even though red berries often look good they can be poisonous. But if something tastes sweet you can be fairly sure it's good to eat. When a clue is this reliable, taking the time to associate it with hunger is unnecessary and wasteful. It's much more efficient to have the neurons connected from birth. And this hard-wiring must have been the next stage in development: we can see it in human babies who when tasting sweet liquids seem to experience pleasure.*4

These hard-wired associations were strong associations. When two stimuli are strongly associated the responses to either stimuli are the same. So with Pavlov's dogs, both the bell and food produce the same salivating response. We can be fairly sure, too, that both the bell and the food produce pleasurable feelings and that the pleasure given by either stimuli increases when the dogs are hungry and decreases when the dogs are well-fed. In other words the pleasure from each stimulus mirrors the other.

Clues and super clues

By becoming hard-wired a sweet taste became more than just another pleasurable clue. It became a super clue. Because the pleasure it gave reflected the relief of hunger, it could now act as hunger by proxy. Because sweet snacks taste better when we are hungry, we don't always have to be aware of feeling hungry.*5 All we have to be aware of is liking sweet snacks. That might give us the false impression that the pleasure of the sweet snack is motivating us, when in fact we are being motivated by the pain of hunger.

The same is probably true for all activities we believe we do purely for pleasure: somewhere in the background we are being motivated by a painful stimulus that we may not be aware of. For instance you might not always notice that you are sex-starved, but instead you will probably be aware that some secondary sex characteristics – breasts, chests, buttocks, hips, thighs – are more alluring than usual. You might believe that these pleasurable clues are motivating you but actually it's the pain of being sex-starved which is doing it. Similarly you may not always feel the pain which makes you want to look after children. You would feel it, though, if you became separated from your children. It's the same pain that makes some unbalanced people steal babies from hospital wards.

Hierarchies of pleasure

Not all clues are hard-wired. Most clues in humans are learned and through learning they may become anything from strongly to moderately to weakly associated with a painful stimulus. Depending on how strongly they are associated and depending on how painful the stimulus is, different clues give different intensities of pleasure. These different intensities of pleasure allow us to prioritise clues. Given a choice we would rather eat food than smell it because eating is usually much more pleasurable than smelling. But let's say we have had more than enough to eat. Then neither eating nor smelling are very appealing and we might choose to do another activity instead which is now more pleasurable – such as going to the cinema to see a film.*6

A summary with contradictions

So by linking clues to painful stimuli, clues are given different weightings of pleasure which make it more or less likely that animals will pursue them. The aim of pursuing clues is always to get rid of painful stimuli. The more pleasurable a clue is, the greater the chance is (in the brain's estimation) that it will lead to this aim. Clues are pleasurable because pleasure promotes the formation of new concepts and these concepts can help an animal get what it wants. Some pleasurable clues, though, have an additional function: they can act as proxies for painful stimuli if they are strongly associated with them. This is because the amount of pleasure they give mirrors the amount of relief an animal would feel if they got rid of the painful stimuli.

These conclusions might seem logical enough but they would be much more convincing if I could show what is happening in the brain. How do neurons connect up so that the pain of a painful stimulus increases the pleasure of a pleasurable clue? This is a question I hope to address in a post in the near future.

Before I do, though, I have to understand why some clues and stimuli don't appear to fit the pattern. Some clues – such as noticing the toothpaste is running out – feel neither pleasurable nor painful. But how would concepts form if there is no pain or pleasure? On the other hand some stimuli – such beautiful mountain views - feel pleasurable although they seem neither to be clues nor relieve pain. But why would brains give pleasure for no reason at all? I'm going to try and explain these contradictions in the next post.

*1. This is a simplified model: in reality the feeling of hunger may be caused by a combination of painful stimuli.

*2. In the case of hunger we could say that the stimulus is glucose. But we could also say (at a stretch) that there are two stimuli – a low glucose concentration which could be called a painful stimulus; and a higher glucose concentration which could be called a favourable stimulus. I use the terms painful and favourable stimuli in this unorthodox way to mean the two flip sides of the same coin.

*3. Pleasurable clues are salient clues and salience promotes the formation of concepts. See Learning for a detailed explanation.

*4. See Pleasures of the Brain by Kent C. Berridge

*5. This state of being hungry without feeling hungry is only likely to happen when we are slightly peckish. If the pain of hunger is strong we are usually aware of it.

*6. There is probably no hierarchy of needs as envisioned by the psychologist Abraham Maslow. At any one time our needs and wants depend on the intensities of the different pains we are feeling and the pleasures of clues strongly associated with them. Our pains and pleasures vary greatly in different circumstances and that means our needs can never be as neatly ordered as Maslow imagined.