The Secret Life of the Mind

by Mariano Sigman

  Sniffing out love

  Perhaps the most important and complex decisions that we make are social and emotional. It may seem strange, almost absurd, to decide whom to fall in love with in a deliberate way, by some arithmetic evaluation of arguments for and against that person we feel so drawn to. That’s just not how it works. We fall in love for reasons that are generally mysterious and can only be determined sketchily after some time has passed.

  At pheromone parties, each participant sniffs the clothing that’s been worn for a few days by other guests. Based on the odour print that attracts them, they decide whom to approach at the party. Choosing this way seems natural because we associate our sense of smell with intuition, like when we say that ‘something smells fishy.’ And because we all recognize how evocative the intimate and indescribable scent of our lover’s sheets is. But, at the same time, it’s weird because, obviously, our sense of smell isn’t the most precise of our senses. So it seems fairly likely that someone could be sorely disappointed by the partner their sniffing leads them to, and run off cursing their ridiculous nose.

  Claus Wedekind, a Swiss biologist, made a phenomenal experiment out of this game. He had a group of men wear the same T-shirt for several days, with no deodorants or perfumes. Then a series of women smelled the shirts and articulated how pleasurable they found each scent–and, of course, he also did the reverse, having the men sniff the women’s well-worn T-shirts. Wedekind wasn’t just fishing with this experiment to see what he would find: he had based it on a hypothesis constructed from observing the behaviour of rodents and other species. He was exploring the premise that as far as scent, taste and unconscious preferences were concerned, we are very similar to our inner ‘beasts.’

  Each individual has a different immune repertoire, which explains, in part, why, when exposed to the same virus, some of us get sick and others don’t. We can think of each immune system as a shield. If two shields are placed one on top of the other protecting the same space, they become redundant. However, two shields covering different, contiguous spaces can together protect a larger surface area. The same idea can be transferred–with certain drawbacks that we will ignore for the moment–to the immune repertoire: two individuals with very different immune repertoires give rise to progeny with a more effective immune system.

  In rodents, who use their sense of smell much more than we do when choosing a mate, the preference largely follows a simple rule governed by this principle: they tend to choose mates with a different immune repertoire. This was the basis for Wedekind’s experiment. He measured each participant’s MHC (major histocompatibility complex), a family of genes involved in the differentiation between our own and others’ immune systems. And the extraordinary result is that when we judge by our sense of smell, we do so according to the same premise as our rodent cousins: on average, women will be more attracted to the scent of men who have a different MHC. So pheromone parties* promote diversity. At least in terms of immune repertoires.

  But this rule has a notable exception. A female mouse’s scent preferences invert when she is pregnant. Then she prefers the smell of mice with MHCs that are similar to hers. The simplified, narrative version of this result is that while the search for complementariness can be beneficial when mating, once there is already a baby in the womb it makes sense to remain close to a known nest, among kin, with those who are similar.

  Does the same shift in olfactory preference happen with women? It seems plausible since, in the midst of the hormonal revolution that occurs during a woman’s pregnancy, her changes in smell and taste perception are among the most distinctive effects. Wedekind studied how olfactory preference changed when a woman is taking birth control pills with steroids that stimulate a very similar hormonal state to pregnancy. Thus it was discovered that, just like in rodents, the result was turned on its head, and the smell of T-shirts worn by men with similar MHCs became more appealing.

  This experiment illustrates a much more general concept. Many of our emotional and social decisions are much more stereotypical than we recognize. In general, this mechanism is masked by the mystery of the unconscious and, therefore, we do not perceive the process of deliberation. But it is there, in the underground workings of an apparatus that may have been forged long before we were able even to begin pondering these questions.

  In short, decisions that are based on hunches and intuition, which because they are unconscious are often perceived as magical, spontaneous and unfounded, are actually regulated and sometimes markedly stereotypical. According to the mechanical virtues and limitations of our awareness, it seems wise to delegate ‘simple’ decisions to rational thought and leave the complex ones to our smell, sweat and heart.

  Believing, knowing, trusting

  When making a decision, in addition to carrying out the chosen option, the brain generates a belief. That is what we perceive as trust or conviction in what we are doing. Sometimes we buy a chocolate bar at a kiosk, certain that it’s exactly what we want. Other times we walk away hoping that the chocolate sweetens our frustration at knowing we haven’t chosen well. The treat is the same, but the bitter perception of having made a clumsy decision is very different.

  We have all, at some point, blindly trusted a decision that later turned out to have been wrong. Or, conversely, in many situations we act without conviction when we actually have all the arguments to be heady with confidence. How is this feeling of trust in our decisions constructed? Why do some people constantly walk around excessively confident, no matter what they do, and others live in doubt?

  The scientific study of this trust–or hesitation–turns out to be particularly tempting because it opens up a window on subjectivity; it is not a study of our observable actions but rather of our private beliefs. Which is not to say that it is a minor matter from a purely practical standpoint, since our confidence (or lack thereof) in ourselves and our actions defines our manner of being.

  The simplest way to study confidence is asking someone to draw a point on a line where one end represents absolute confidence and the other represents doubt about a decision that’s been made. Another way to detect confidence is by asking the decision-makers if they prefer to charge a fixed amount for the decision or make a bet on it to earn more. If they are very confident about the decision they’ve just made, they’ll be inclined to bet (two birds in the bush). If, on the other hand, they are hesitant about their choice, they’ll prefer the fixed amount (bird in the hand). These two means of measuring confidence are very consistent; those who display firm conviction on the line model also bet boldly. And the opposite is also true: those who tend to express low confidence in their decisions are not inclined to bet on them.

  This parallel between confidence and betting has obvious relevance for daily life. Betting or investing poorly in financial, emotional, professional, political and family questions has a high cost. But this parallel also has scientific consequences. This type of experiment allows us to question our subjectivity in areas that previously seemed to be impossible to broach. When measuring someone’s predisposition to betting we are discovering something about confidence perceived by those who cannot express their beliefs in words.

  Confidence: flaws and signatures

  The way each person constructs confidence is almost like a digital footprint. Some people express confidence with intermediary nuances, and others with extreme doubt or conviction. There are also cultural traits, and the ways certainty is expressed in some parts of Asia differs from how it is expressed in the West.

  Almost all of us have witnessed examples where we assign confidence in a fairly imprecise way, such as when we think we did well in an exam and it turns out we failed it. And most of us have also known people who are quite accurate in assessing their own knowledge and therefore have a precise, dependable sense of confidence, knowing when to bet and when not to. Confidence is then a window into one’s own knowledge.

  The accuracy of one’s confidence is a personal trait, similar to heigh
t or eye colour. But unlike those physical traits, there is a certain amount of space to change and modify this thought pattern. As an identity trait, it has a signature in the brain’s anatomical structure. Those who have more accurate confidence systems have a greater number of connections–measured in density of axons–in a region of the lateral front cortex called Brodmann Area 10, or BA10. Additionally, those with a more precise sense of confidence organize their cerebral activity in such a way that this BA10 region is more efficiently connected to other cortical structures in the brain, such as the angular gyrus and the lateral frontal cortex.

  This difference in functional brain connectivity between those who have an accurate sense of confidence and those who don’t is only observed when a person turns their attention inwards–for example, by focusing on their breathing–and not when their attention is focused outwards on the external world. This establishes a bridge between two variables that were seemingly scarcely related: our sense of confidence and our knowledge of our own body. What they have in common is that they both lead our thoughts inwards. And that suggests that a natural way of improving accurate confidence in our decision-making system is learning to observe and focus on our own body states.

  To sense whether we trust ourselves or not, our brain uses endogenous variables. For instance, it will sense lack of confidence if we sweat, stutter, lower our gaze or express other bodily signs of doubt. These body signs, which we use to sense confidence in others, also allow us to sense that about ourselves.

  The nature of optimists

  When the balance between doubt and certainty applies to outcomes in the unknowable future, our sense of confidence divides us into optimists or pessimists. Optimists are sure they will make every shot, win every big game, never lose their job and can have unprotected sex or drive recklessly because, after all, they are immune to the risks. What’s mysterious is how optimism survives despite knock-backs and the evidence to the contrary we receive each and every day. The solution to this conundrum in an optimist’s brain is selective forgetting. Every Monday, like every 1 January, is filled with repeated promises; every love is the love of our lives, and this year we are absolutely going to win the championship. Each of these affirmations completely ignores the fact that there have been plenty of other Mondays and plenty of other disappointments. Are we really so blind to the evidence? What are the mechanisms in our brains that bring about this fundamentalist adherence to optimism? And what do we do with this persistent optimism while accepting that it’s based on an illusion?

  One of the most common models of human learning–now delegated chiefly to robotic and artificial intelligence–is the prediction error. It is simple and intuitive. The first premise is that each action we realize, from the most mundane to the most complex, is built on an internal model, a sort of simulated prelude to what will happen. For example, when we greet someone in a lift we are presuming that there will be a positive response from that person. If the response is different from what we are expecting–exaggeratedly warm or coldly reluctant–we are surprised.

  Prediction error expresses the difference between what we expect and what we actually observe, and that is codified in a neuronal circuit in the basal ganglia, which generates dopamine. Dopamine is a neurotransmitter whose functions include being a messenger of surprise when travelling into various brain structures. The dopaminergic signal recognizes the dissonance between what is predicted and what is found, and it is the fuel of learning because circuits irrigated with dopamine become malleable and predisposed to change. In the absence of dopamine, neuronal circuits are generally rigid and not very malleable.

  The cyclical renewal of our hopes, every Monday and every New Year’s Eve, forces us to hack into this learning system. If the brain didn’t generate a signal of dissonance when reality is worse than what we were expecting, we would indefinitely renew our hopes. Is that what happens? And if so, how? Is this the optimist’s secret gift?

  All these questions are answered in unison by a relatively simple experiment conducted by a British neuroscientist, Tali Sharot. In it, she asks people to estimate the probability that various unfortunate events would occur. What is the likelihood of dying younger than sixty years old? What about developing a degenerative disease? What about having a car accident?

  A large majority of those asked assume that the odds of something bad happening to them are lower than what statistics suggest. Which is to say, when trying to evaluate our risks–flying in a plane and urban violence are clear exceptions–we are almost all decidedly optimistic.

  But the most interesting thing is what happens when our beliefs do not coincide with reality. For example, in the experiment, participants were asked to estimate the likelihood of suffering from cancer and later on were told that the average likelihood of someone like them doing so is close to 30 per cent.

  According to the model of prediction error, people should use this information to modify their beliefs. And that is exactly what happens when most people discover that things are better than they supposed. Participants who believed that their likelihood of suffering from cancer was worse than in reality adjusted their outcomes to a value very close to the real one. For instance, those who believed that their likelihood was 50 per cent responded in subsequent interviews with values around 35 per cent, which is quite close to the real value of 30 per cent.

  But–and herein lies the key–those who believed that their probability of suffering cancer was less than in reality (for instance those responding that it was 10 per cent) changed their beliefs very little. When asked again in subsequent interviews and after having heard the bad news that the likelihood of suffering from cancer was in fact 30 per cent, they adjusted their estimates by a mere 1 or 2 per cent (to 11 or 12 per cent). That is to say, the adjustment those people make is much less–almost nil–when they discover that the truth is worse than they imagined it to be.

  And what happens meanwhile in the brain? Every time we discover a desirable or beneficial piece of information, a group of neurons in a small part of the left prefrontal cortex called the inferior frontal gyrus is activated. On the other hand, when we receive undesired information, another group of neurons activates in the homologous region on the right hemisphere. A sort of equilibrium between the good and bad news is established between these brain regions. But this equilibrium has two traps: the first is that it focuses much more on good news than on bad, which, on average, creates a tendency towards optimism; and secondly–and most interestingly–the bias in the balance varies from person to person, thus revealing the machinery behind optimism.

  The activation of neurons in the frontal gyrus of the left hemisphere is similar in everyone when we discover that the world is better than we had thought. On the other hand, the activation of the frontal gyrus of the right hemisphere varies widely from one individual to the next when we find out that the world is worse than we believed it to be. In more optimistic people, this activation is minimized, as if they literally turned a blind eye on bad news. In more pessimistic people, the opposite happens; the activation is amplified, accentuating and multiplying the impact of that negative information. Here is the biological recipe that separates the optimists from the pessimists: it is not their capacity to value what’s good but rather their ability to ignore and forget what’s bad.

  Many mothers, for example, have only a vague recollection of the pain they experienced during childbirth. That selective forgetting eloquently illustrates the mechanism of optimism. If the pain were much more present in their memory, perhaps we would see many more only children. Something similar happens among newlyweds; none of them believe they will ever divorce. Yet between 30 and 50 per cent of them will, according to statistics that vary based on time and place. Of course, the moment when they swear eternal love–whatever is meant by love and eternity–isn’t the most appropriate time for statistical reflections on human relationships.

  The costs and benefits of excessive or insufficient optimism are pretty tangi
ble. There are intuitive reasons to encourage a certain amount of naïve optimism, since it turns out to be a driving force behind action, adventure and innovation. Without optimism we would never have landed on the moon. Optimism is also associated in a fairly generic way with better health and a more satisfying life. So we could think of optimism as a sort of little insanity that pushes us to do things that we otherwise wouldn’t do. Its flip side, pessimism, will lead to inaction and, in its chronic version, to depression.

  But there are also good reasons to temper excessive optimism when it encourages risky and unnecessary decisions. Conclusive statistics associating the risk of car accidents with being inebriated, using a mobile phone or not wearing a seatbelt continue to pile up. Optimists know these risks but act as if they are immune to them. They feel they are exempt from the statistics and this, of course, is false: if we were all exceptions, the rule would not exist. This expansive optimism–which usually does not consider itself as such–can lead to fatal yet avoidable consequences.

  Odysseus and the consortium we belong to

  A much more mundane example of excessive optimism is our waking up each day. Often bedtime is filled with promises about the next morning: we plan to get up much earlier than usual to, for example, exercise. That intention is built on a genuine desire and on an expectation of some value to us, such as increased health and fitness. But, except for larks, the panorama the next day is a very different one. The person who made the decision the night before to get up early disappears by next morning. At 7 a.m. we are somebody different altogether, overcome by sleepiness and the strictly hedonistic pleasure of staying in bed.