Brain: an apparatus with which we think we think.
Ambrose Bierce
Our species and its ways of thinking are a product of evolution, not the purpose of evolution.
Edward O. Wilson, Consilience
Why is it so hard to be rational? In the last chapter we saw that our moral deliberations are usually driven by intuition and emotion, not reason. This applies in fact to most of our decisions and beliefs; millions of Americans won’t get vaccinated, and many believe in conspiracy theories or pseudoscience. Even the most rational people I know need to constantly inspect their thought processes for faults. We often conflate intelligence with rationality, which is not the same thing. No one doubts that Elon Musk is a smart person. But for most observers his acquisition of Twitter, apparently overpaying by billions of dollars over its “fair” price, appeared irrational. His claim that he bought Twitter to “help humanity” sounds like a rationalization to justify the illogical.[1]
One barrier that has hindered our understanding of rationality is the notion of duality, which has deep roots in religion and philosophy. For example, Plato argued that, as the body is from the material world, the soul is from the world of ideas and is thus immortal. He believed the soul was temporarily united with the body and would only be separated at death when it would return to the world of Forms. For Plato, ideas (or Forms) are the true reality, and are experienced by the soul.
Descartes, on his part, thought that the mind is a nonphysical substance. He was the first to clearly identify the mind with consciousness and self-awareness and to distinguish this from the brain, which was the seat of intelligence. Hence, Descartes was the first to formulate the mind-body problem in the form in which it exists today. His main argument that the mind is a nonphysical substance is known as dualism. A dualist view of reality may lead one to consider the corporeal as little valued and trivial. In fact, some dualists have gone as far as to propose that all mind-body interactions require the direct intervention of God.[2]
Nowadays, most scientists are convinced that the only thing that exists is matter; that all things are composed of matter and all phenomena, including consciousness, are the result of material interactions. In other words, matter is the only substance. One of the most active areas of neuroscience research is how our brains give rise to our thoughts. While there are still many gaps in our knowledge, there is evidence that the mind is produced by the activity of the brain. For example, as we shall see in the next chapter, the decisions that a person makes can, in at least some contexts, be detected a few seconds earlier by means of scanning their brain activity.
If the mind emerges from the activity of the brain, as the evidence suggests, then it complies with the laws of nature; it is exposed to the pressures of natural selection just as the rest of our body is. This is an obvious statement, but it has profound implications. As we shall see next, understanding the mind as an evolved organ can shed much light about its capabilities as well as its limitations as a reasoning tool.
Why have humans become so smart?
During our evolutionary history, the human brain grew in volume from about 600 cc in Homo habilis to 1,100 cc in Homo erectus, a close relative of humans, and to about 1,350 cc in Homo sapiens. The fastest growth seems to have occurred in the last 2 million years, a short period by evolutionary standards (see also Idea 2). Brains are expensive resources to maintain: Although the brain accounts for 2% of the person’s body weight, it consumes 20% of the body’s energy. They also have specific thermal and regulatory requirements. The evidence shows that our brains grew at the expense of other body tissues. One hypothesis is that the increased energetic demands of a larger brain were offset by a corresponding reduction of the gut. As their guts got smaller, humans changed their diets to high-quality, easy to digest foods.[3]
Why did our brains get so big if they are so costly? Ironically, it was probably our helplessness as a species that contributed to the enlargement of the brain. Compared to other species, humans were sometimes poorly equipped for the task of food procurement. “Very little about our forebears could have inspired confidence,” writes the anthropologist Robin Fox, “not the stature, the speed, the strength, the ferocity… And the answer to this ultimate success can only lie in the very helplessness of the original creature.”[4] Instead of relying on brute force to procure food, according to this hypothesis, our ancestors thrived because of larger brains.
But nutrition is only a means to an end: reproduction. In fact, the evolutionary success of a species depends on the success of its reproductive strategy. Sex is, of course, the way most species reproduce. In his 1871 book, The Descent of Man, and Selection in Relation to Sex, Charles Darwin argued that evolution is driven not just by natural selection, but by a process called sexual selection: same-sex competition and mate selection. The former involves members of one sex competing among themselves in various contests, physical or otherwise, the winners of which gain preferential sexual access to mates. The latter deals with preferential mate choice: if members of one sex exhibit traits that are attractive to the other sex, they will have a mating advantage. Those lacking attractive traits get shunned and remain without mates or must settle for low quality mates. Those sexual qualities that lead to reproductive success become more dominant in the population.
Darwin’s ideas on sexual selection were considered highly controversial in his time and relatively neglected for almost a century after its publication. Today, sexual selection has become a central theory in evolution and most experts now agree that our choice of mates has been a critical factor in human mental evolution. In its modern form, sexual selection theory provides answers to questions that would be confounding otherwise, such as why the male and female minds differ, why most murderers are men, and why is conflict between the sexes so pervasive. Some researchers even argue that sexual selection is responsible for the more “self-expressive” aspects of human behavior, such as art, morality, language, and creativity.[5]
It is doubtful, though, that food procurement and mate selection problems by themselves could account for the adaptations that resulted in the extraordinary flexibility and cognitive abilities of the human brain. The other prime suspect is social life. As with food procurement and sex selection, the problems and opportunities presented by social interactions created strong adaptive pressures that, most likely, contributed to the increases in cognitive ability. In primate species, for instance, there is a strong positive relation between group size and brain size: (terrestrial) species that live in large groups have bigger brains than do other species.[6]
What was so unique about human social interactions? After all, other species also exhibit complex social lives. In his book Chimpanzee Politics: Power and Sex among Apes, Frans de Waal, a long-time student of simian behavior, presents a Machiavellian tale of coalitions, deception, coups, and countercoups among male chimpanzees in the Arnhem Zoo, in Holland. De Waal observes that the maneuvering males acted with considerable subtlety, as though they had read Machiavelli. They communicated by sound and gesture, formed bands along what can only be called political lines, and engaged in what is clearly organized warfare.
Why then chimpanzees did not develop the same level of self-awareness and intelligence that humans did? The answer may lie in the particular social structure of ancestral hominid groups. Most likely, they maintained a relatively loose and flexible social structure in which status differentiation was somewhat flexible and dependent on the circumstances. In such structures,[7]
One does not always know where one stands in the group. Instead, one must engage in numerous cognitive tasks to determine one’s social standing. One must pay attention to the situation and remember how one interacted with a given subgroup at any point in time. In such groups, interaction and coordination pose a tremendously complex cognitive problem, and part of the solution to this problem might have been the eventual development of a symbolic self that could better keep up with rapidly changing situations, subgroups, and interactions.
This is an accurate description of the type of social interactions that are characteristic of practically all cultures on earth. The flexible and ambivalent social nature of our human ancestors probably contributed to the evolution of the brain, in both its enlargement and its differentiation. This ambivalence is pretty much part of our human heritage, and it defines many of the behaviors and attitudes observed in human relationships, even today.
Taken together, the search for food, the selection of mates, and complex social interactions may have pushed our pre-human ancestors toward the formation of the earliest communities around fixed camps. According to the preeminent American evolutionary biologist Edward O. Wilson, this was the most critical step in our road to becoming fully human. “When humans started having a camp – and we know that Homo erectus had campsites – then we know they were heading somewhere,” Wilson stated in a 2011 interview. “They were a group progressively provisioned, sending out some individuals to hunt and some individuals to stay back and guard the valuable camp site. They were no longer just wandering through territory emitting calls. … They began to read intentions in each other’s behaviors, what each other are doing. They started to learn social connections more solidly.”[8]
Understanding our evolutionary history goes a long way to explaining the astounding versatility and flexibility of the human brain (as well as its limitations). For example, humans are sensitive to certain sounds, especially those made by predators, such as the lion, whose roar we can hear from far away. In contrast, humans are unable to perceive low frequency sounds and ultraviolet light because these functions were not crucial for their survival. Many vertebrates, by contrast, see colors in that part of the spectrum invisible to humans.[9] Our sense of smell is also limited compared to other species. For example, snakes in general have a strong sense of smell which they use to make up for their poor eyesight and limited hearing.
Did the brain evolve to be a persuasion tool?
Being social animals, humans can recognize other individuals and read their emotions from glimpses of their faces. This happens effortlessly, without conscious intervention, an amazing feat that the fastest supercomputers have yet to emulate. These highly specialized functions performed by the brain have led some researchers to propose a modular structure for the brain, with each module solving a specific adaptation problem. Each module performs its function efficiently, beyond people’s conscious awareness. People may be aware of having reached a certain conclusion, but they are never aware of the process itself.
This is the foundation of a discipline known as evolutionary psychology (or EP), which posits that much of human behavior is the output of psychological adaptations that evolved to solve recurrent problems in human ancestral environments. Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations including the abilities to infer others’ emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate (or not) with others.[10]
While many of the claims of EP remain controversial and speculative, its “adaptationist” approach is steadily increasing as an influence in the general field of psychology.[11] One of the most contentious areas of research, however, is in the adaptive value of higher order brain functions such as reasoning and consciousness. Rationality and self-awareness are considered the crowning achievements of our species. But what exactly are the adaptive problems these functions solve? I will leave the discussion of consciousness for Chapter 6, when I talk about free will. Here I want to investigate the adaptive function and possible evolution of reasoning.
The adaptive value of reasoning should be obvious: It allowed humans to acquire knowledge and to use it effectively to produce better tools and weapons and use them against predators and other competing groups, including their cousins, the Neanderthals. Most researchers believe that the main function of reasoning is to enhance individual cognition, or the ability to acquire knowledge and assess evidence, a view that harks back to Descartes and to the ancient Greek philosophers. Another hypothesis is that reasoning gives humans the possibility to deal with novelty and to anticipate the future, although this is more related to learning.
But is enhanced individual cognition really the primary function of reasoning? Consider our ability to walk. Humans became bipedal about six million years ago most likely because in the newly created savannas animals with improved terrestrial locomotion were able to survive better than their arboreal ancestors. After becoming bipedal, humans were able to run, dance and go water-skiing (even though bipedalism did not evolve for this purpose). Nonetheless, the study of human posture shows that our feet are better adapted for walking than for running, and this is strong evidence that walking is their main function. In other words, our ability to run and dance is a byproduct of our ability to walk, which was selected by evolution, [12]
Box 10: Human Reasoning: Selective Trait or Byproduct of Evolution? One of the most distinctive traits of the human brain is its ability for logical thinking. But could it be that this trait is not the product but the byproduct of evolution? (That is, a skill, like dancing, that humans developed from a trait favored by evolution, like walking, see main text). The evidence shows that humans are not so good at solving logical tasks but are good at understanding the actions and intentions of others, a skill that our ancestors most likely had even before they developed a sense of self. Imagine a set of four cards with letters on one side and numbers on the other. A man of uncertain trustworthiness tells you: “if one card has a D on one side, it should have a 3 on the other.” The four cards on the table show the following:
What are the cards that should be turned over to determine the truth of what this person said? The psychologist Peter Wason found that most people give the wrong answer: although most people know that the card with the letter D should be flipped, only 10 % realized that only one other card, the one with the 7, should be verified. When subjects were asked to give reasons for their choice of cards, the reasons given are often rationalizations that they think afterward to explain their choices, rather than true determinants of the choice. For example, in the card experiment, people tend to choose the D and 3 cards simply because they are both mentioned in the rule itself.
Now, imagine that you are a government inspector and that you go into a bar where there is one person drinking beer, one drinking a soda, one twenty-five-year-old, and one sixteen-year-old. The law says that only those eighteen years old or older can drink beer. To which of these clients you should ask for their IDs to verify their ages? This is the same as the card problem above:
Leda Cosmides, who performed this experiment as part of her doctoral dissertation, found that almost all gave the correct answer: You do not need to ask the ID to the person drinking soda and the 25 years old, but the one drinking beer and the underage person.
These two problems have the same logical structure. The difference is that the second problem is presented in terms of breaking a rule – something people are particularly good at detecting – which makes it easier to solve. In general, humans seem to be good at detecting violations to social contracts, that is cheaters, and not so good at detecting logical violations, per se. In short, we are not so good at solving abstract logical problems, although our minds allow us to think logically.
See: Cosmides, L. (1989). The logic of social exchange: Has natural selection shaped how humans reason? Studies with the Wason selection task. Cognition, 31, 187-276.
Humans do have the capacity to reason logically, and collectively, humans have been able to send a man to the moon. Individually, however, humans often have weak reasoning powers. Many studies show that our judgment is greatly influenced by how the evidence is presented to us. For example, a study found that when pieces of evidence are doled out one at a time, instead of being shown all at once, people conclude that the evidence is stronger.[13]
Why is that humans are not always great at making rational decisions? Some researchers have suggested that the most important function of reasoning is not the pursuit of truth, but to devise and evaluate arguments intended to persuade fellow humans. That is, the core function of reasoning is argumentative. This hypothesis is known, fittingly, as the argumentative theory of reasoning.[14] According to its proponents, the evidence of humans’ pitfalls in making decisions, can be best interpreted and explained considering this hypothesis. In their view, it is not so much that human reasoning is deeply flawed, but that it is remarkably efficient for certain types of social and cognitive interactions at which it excels (see also Box 10).
In other words, reasoning can lead to poor outcomes, because humans strive for arguments that justify their beliefs and actions. A case in point is confirmation bias, whereby we seem motivated to seek confirmatory evidence for our beliefs and we fail to look for disconfirming evidence. This may help us to persuade others, which is highly adaptive, given our exceptional dependence on communication, but it distorts our attitudes and evaluations.
It also allows erroneous beliefs to persist even when they have been proved to be ill-founded. Consider, for example, the task of testing the rule “if one card has a D on one side, it should have a 3 on the other,” shown in Box 10. People usually fail at this task because most select, correctly, the card that confirms the rule (D), but many ignore the card that disconfirms it (7). People turn out to be more logical when they want the rule to be false.
Our biased brain
Conformation bias is related to motivated reasoning, when emotional biases lead to justifications or decisions based on their desirability, rather than an accurate reflection of the evidence. Motivated reasoning is the “tendency to find arguments in favor of conclusions we want to believe to be stronger than arguments for conclusions we do not want to be.”[15] Motivated reasoning and confirmation bias stand in contrast to critical thinking, where beliefs are approached in a skeptical and unbiased fashion.
As it happens, our decisions are often influenced by many other cognitive biases: systematic patterns of deviation from norm and/or rationality in judgment (see Box 11). This is just how our brains work, but they can lead to bad or poor choices. We all want to believe that the professionals on which our health and laws depend are logical, meticulous thinkers who perfectly and impartially weigh the pros and cons of treatment and legal options, acting as unbiased surrogates for patients and citizens. This is often, alas, not the case. Like all mortals, cognitive bias affects how doctors and judges think and the treatment and legal decisions they make.
Box 11: The Cognitive Biases that Impact Our Decisions We all suffer from confirmation bias, the motivation to seek confirmatory evidence for our beliefs. This is, however, one of numerous psychological phenomena that reveal cognitive limitations in humans. In the 1970s, psychologists Daniel Kahneman and Amos Tversky did a series of landmark experiments and revealed twenty or so “cognitive biases” – unconscious errors in reasoning that distort our judgment of the world. Since then, many other cognitive biases have been studied and identified. Wikipedia lists more than 150 biases. Here are a few of them: Authoritarian bias is the tendency to believe people who hold positions of power and status. We give them more credence without checking their sources (see the discussion of Zimbardo’s Stanford Prison and Milgram’s Obedience experiments in Idea 5). Cause-and-Effect bias refers to the predisposition of our brain toward making a causal connection between two events, even when no such connection exists. If you take an herbal remedy and your cold disappears, you will attribute the cure to the remedy, even though dozens of other unrelated factors can be involved. Anchoring bias occurs when people base subsequent judgments on previously given information, even if those initial starting points are irrelevant. For example, people who were asked to estimate Gandhi’s age gave higher numbers when they were first exposed to the number 115 than if they were initially exposed to the number 35. This suggests that the initial starting point influenced the subsequent estimate and biased the estimate towards the initial value. Group Consensus bias: the more other people agree with us, the more likely we will be to assume that our beliefs are true. Conversely, the more people disagree with us, the more likely we’ll be to suppress and doubt our own beliefs, even if they are correct. Logic bias is the tendency to believe arguments that strike us as more logical. We also tend to ignore information that does not make sense to us. As William James said, “As a rule we disbelieve all the facts and theories for which we have no use.” Loss aversion is the tendency to prefer avoiding losses to acquiring equivalent gains. This is prominent in the domain of economics. What distinguishes loss aversion from risk aversion is that the utility of a monetary payoff depends on what was previously experienced or was expected to happen. Studies have suggested that losses are twice as powerful, psychologically, as gains. See: Tversky A. & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185, 4157, pp. 1124-1131. Also, https://en.wikipedia.org/wiki/List_of_cognitive_biases.
There are many documented cases of racial biases in treatment and legal decisions by physicians and magistrates. For example, one study found that black patients were significantly less likely than white patients to receive pain medication in the emergency department, despite reporting similar levels of pain. Other research suggests that longstanding racial biases among judges might have contributed to racial differences in how justice is administered. However, a growing body of scientific research on physician and judicial decision-making shows that doctors as well as judges exhibit other cognitive biases that influence the way they think, and how they treat patients and come up with court decisions. These biases lead doctors and judges to make the same mistakes as the rest of us, but usually at a greater cost.[16]
Just a word of caution. You may conclude from our discussion that human thinking is intrinsically flawed or irrational. As we have seen, there is much evidence that reasoning is not the main function of the brain, which might explain why humans are not always perfectly rational. However imperfect, the human mind has allowed our species to thrive and conquer basically all environments on Earth. Indeed, a growing number of researchers see the biases described above not as failures in our decision making, but as a byproduct of how our mind evolved to adapt and cope with the real world. For example, when getting to know others, people tend to ask leading questions which seem biased towards confirming their assumptions about the person. Nonetheless, this kind of confirmation bias has also been argued to be an example of social skill; a way to establish a connection with the other person.[17]
To conclude: Keep your mind open and challenge your own beliefs
The argumentative theory is still young and like other theories may be subjected to corrections and modifications in years to come. The theory fits the scientific evidence and makes sense of current events such as the polarization of our society and political system, and the proliferation of conspiracy theories. It also explains why we have more rhetoric than fact in our national policy making, and why politicians and Supreme Court justices are more interested in creating compelling narratives to win arguments, or to rationalize their seemingly contrived legal decisions, rather than being logical and truthful.
One tragic example of this are the narratives regarding the role of guns in mass shootings in the United States, which has had more than any other country. To any objective observer, the common factor is easy accessibility to assault weapons. There have been over 2,000 mass shootings since 2013, roughly 0.62 per day, about half of which – and six of the ten deadliest – were committed with semi-automatic rifles.[18] There are people with mental issues in every country, but only in the USA can they buy deadly assault weapons almost without any restriction. This should be obvious to every rational person. Yet, politicians, mainly Republicans, really do not want to acknowledge that the reason the United States has such exceptional levels of gun violence is its exceptional obsession with, and access to guns. That, after all, might imply the need for additional restrictions on the availability of firearms, which is opposed by the powerful gun lobby. Instead, they have tried to deflect blame by arguing that the main issue is “mental health” (while simultaneously cutting access to mental health care), or they’ve been blaming schools for being “soft targets.” These appear to be rationalizations rather than convincing arguments.
It doesn’t have to be like this. Collaboration and intergenerational cooperation have led to the highest of human achievements. Isaac Newton said it best when he wrote to his rival, Robert Hooke, that he was able to see “a little further by standing on the shoulders of giants.” Even Einstein relied on the ideas of others to produce his amazing theories. He probably would have been unable to formulate his greatest achievement, the general theory of relativity, without the assistance of his mathematician friend Marcel Grossmann, who helped Einstein develop the quantitative tools needed for the theory. It is important to understand the factors that promote this kind of cooperation.
Even if the argumentative theory is proven wrong, we all need to have cognitive humility, as we are not as smart as we think we are. It is increasingly clear that the brain is poorly adapted to deal with the cognitive demands of the modern age, particularly in situations with many options to choose from. We should start by acknowledging our cognitive biases (see Box 11), then find out in what situations they can become a problem or a hindrance. We should also strive to make the best of our limited cognitive resources by using them wisely (see also Idea 9). These are important topics that I will be discussing in the rest of this chapter.
[1] “Elon Musk claims he's buying Twitter to 'help humanity',” by James Clayton, BBC News, Oct 27, 2022. [2] See, e.g., Lewis, C. S. (1947). Miracles. For a general discussion on dualism see Robinson, H., "Dualism", The Stanford Encyclopedia of Philosophy (Fall 2003 Edition), http://plato.stanford.edu/archives/fall2003/entries/dualism/. [3] Aiello, L. C. & Wheeler, P. (1995). The expensive-tissue hypothesis, Current Anthropology, 36, 199-221. See also Stedman, H. H. et al. (2004). Myosin gene mutation correlates with anatomical changes in the human lineage, Nature, 428, 415-418. [4]Fox, R. (1980). The red lamp of incest, New York: Dutton, p.175. [5]Miller, G. (2001). The mating mind: How sexual choice shaped evolution of human nature, Anchor. [6]Dunbar, R. I. M. (1993). Coevolution of neocortical size, group size, and language in humans. Behavioral and Brain Sciences, 16, 681-735. [7] Sedikides, C.& Skowronski J. (2000). On the evolutionary functions of the symbolic self: The emergence of self-valuation motives. In Tesser A., Felson R. B. & Suls J. M. (Eds.), Psychological Perspectives on Self and Identity, American Psychological Association, p. 98. [8] Quoted in “E. O. Wilson’s theory of everything,” by Howard W. French. The Atlantic, November 2011, p.80. [9] As a rule, animals can see and hear what they eat and what can eat them. See, e.g., Ellard, C. (2009). Why We Can Find Our Way to the Moon but Get Lost in the Mall, Doubleday. [10] Buss, D. (2011). Evolutionary psychology: The new science of the mind, (4th ed.), Prentice Hall. [11] Schacter, D. L. et al. (2010). Psychology, (2nd ed.) Worth Publishers. [12] Cunningham, C. B. et al. (2010). The influence of foot posture on the cost of transport in humans. Journal of Experimental Biology, 213, 790-797. [13] Whitman, J. C. & Woodward, T. S. (2011). Evidence affects hypothesis judgments more if accumulated gradually than if presented instantaneously. Psychonomic Bulletin & Review,18, 1156-1165. [14] See e.g., Mercer, H. & Sperber, D. (2011). Why do humans reason? Arguments for an argumentative theory, Behavioral and Brain Science, 34, 57-111. [15]Kunda, Z. (1990). The case for motivated reasoning. Psychological Bulletin. 108 (3): 480–498. [16]See, e.g., “How common mental shortcuts can cause major physician errors,” by Anupam Jena and Andrew R. Olenski, The New York Times Feb 20; Also, Jiang, Y. (2020). Misjudging in Judging: The Role of Cognitive Biases in Shaping Judicial Decisions, Temple Law: Political & Civil Rights Society, Jun 5, 2020. [17] Gigerenzer G. & Todd P. M. (1999). Simple Heuristics That Make Us Smart, Oxford University Press. Also, Dardenne B. & Leyens J. P. (1995). Confirmation Bias as a Social Skill. Personality and Social Psychology Bulletin. 21 (11): 1229–1239. [18]See, e.g., https://en.wikipedia.org/wiki/Mass_shootings_in_the_United_States#Weapons_used .
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