Lisa Barrett’s second book adopts a more accessible approach to writing, distilling the history and research behind eight (the 7 ½ is for the catchy title) key ideas in current psychology and neuroscience. It was a really good read and a definite recommendation to anyone not used to reading psychology literature. It’s very digestible and condenses a lot of complex ideas and debates in a super engaging and interesting way. Here’s a few of my favourite ones.

Lesson 1: The Brain Did Not Evolve for Thinking

This is an idea I’ve often thought about. The brain didn’t evolve for conscious thought, it evolved numerous different mechanisms for survival, of which conscious thought just happens to be one. I believe this is because as a species, our evolution has been more socially oriented than other animals and maintaining such complex social networks on both micro and macro levels is facilitated by advanced conscious thought. 

Barrett illustrates this using the amphioxus, a primitive organism from 550 million years ago. These creatures (which still exist today) couldn’t taste, smell, see, or hear, they simply drifted along the ocean floor waiting for food to drift into their mouth. She describes them as a ‘stomach on a stick’. However, despite their simplicity amphioxi are our evolutionary ancestors.

Through Darwinian evolution (genetic variation + natural selection) the amphioxi developed an ability to sense their environment. They became better at detecting prey and predators and evolved motor systems for more efficient evasion and predation. Following these developments, evolution favoured the creature that could perform these tasks more efficiently. Chasing prey too slowly may mean losing to competition, and fleeing from a non-existent threat wastes resources that might be needed later. In terms of energy budgeting, prediction is better than reaction. If you can prepare a movement in anticipation of a predator, you’re more likely to survive than if you await the attack and react accordingly.

 Evolution favoured the creature that could predict their energy needs accurately and frequently, leading to better exploration, hunting, reproduction, and survival.

This concept is the basis of allostasis. Unlike homeostasis, which maintains a stable body state in a particular moment (e.g., sweating when too hot to reduce body temperature, releasing insulin when blood sugar is too low), allostasis involves predicting and meeting the body’s needs over time. As the ‘stomach on a stick’ evolved to have more complex systems – cardiovascular, respiratory, immune systems, hormonal – managing these systems for allostasis required a central command: the brain.

So, if the question is ‘why the brain evolved’ the answer would be to predict the body’s energy needs so as to use energy most efficiently, or in other words, to oversee allostasis. However, posing this question suffers from the teleological presumption that the brain evolved for something, rather than just simply evolving and happening to end up in a particular direction. Rationality, emotion, thought, imagination, empathy, and other such cognitions we tend to believe are the brain’s main purposes are just secondary byproducts of this evolutionary process.

Lesson 2: The Human Brain is Not More Evolved, Just Differently Evolved

Plato believed that within each human being, three inner forces constantly vie for control over your behaviour: basic survival instincts, emotions, and rational thought. The last is designed to control the first two and help guide you towards a more civilised and virtuous life.

This interpretation has some appeal. All of us have felt that inner conflict between desire and reason at some point. For this reason, Plato’s original idea has been expanded upon over the last 2 millennia. It certainly bears resemblance to Freud’s id, ego, and superego distinction. In the 1960s, Plato’s proposition was mapped and integrated into medical science when Paul MacLean proposed the notion of a triune brain. This theory suggests that our brain evolved in three stages: the reptilian brain first, housing our survival instincts, the limbic, mammalian system second, housing our emotions, and finally the neocortex, thought to be uniquely human and the source of rational thought.

In no uncertain terms, Lisa states that the theory of the triune brain ‘is one of the most successful and widespread errors in all of science’.

The idea that the brain operates with three distinct sections is far removed from current understandings of neurology, despite the frequency with which phrases like ‘our lizard brain’ appear in pop science writing. One key issue is that it succumbs to the anthropocentrism that colours many early attempts to understand the mind. Traditionally, and with much religious backdrop, it was asserted that humans are unique in their ability for rational thought, and were thus superior. Traditionally, rational thought implied the absence of emotion, an idea that supported the notion of the triune brain. However, emotions are often rational, like experiencing fear when near a cliff is rational, and sometimes thinking is irrational, like convincing yourself that failing an exam will ruin your life. Even mental illnesses like PTSD may be considered rational – living in constant anticipation of threat after having been previously exposed to constant threat is a reasonable response. Lisa argues that PTSD symptoms stem from body budgeting gone awry, in that previously rational body budgeting is now out of sync with the immediate environment. She uses this to argue that ‘rational behaviour means making a good body-budgeting investment in a given situation’. Therefore, rationality is not unique to humans, conscious thought just happens to be one of our tools to guide rationality.

Our brains are not more evolved than other species that have made it this far, they’re just differently evolved.

Two key ideas undermine the notion of the triune brain. First, evolutionary neuroscience has shown that the brains of vertebrates develop in the same order, and use the same broad biological building blocks. The difference in appearance and abilities comes from the varying lengths of time each component develops, and our unique human cognitions come from this, not from some superior biological process. Second, our relatively large neocortex is not the reason for our apparent unique capacity for conscious thought. It’s actually just a scaled-up version of relatively smaller cortices found in other, smaller mammals. Equally, it’s a scaled-down version of relatively larger cortices found in larger mammals, like elephants and whales. The way our brain has evolved has definitely conferred advantages, we’ve constructed amazing architecture, developed miraculous medical technology, travelled to space etc. However, other species can regrow limbs, survive in outer space, lift many times their own body weight etc. 

Lesson 3: The Brain is a Dynamic Network of Plastic Neuronal Connections

Having established that the brain is not some internal battleground between rational thought and basic instincts and emotions, it makes sense to look at what it is instead. Barrett is explicit in her description that the brain is a network, or, ‘ a collection of parts that connect to function as a single unit’. I won’t get into the full neuroscience of how neurons communicate with each other, but will include this link, which I find to be one of the coolest and most profound videos I’ve ever seen (https://www.youtube.com/watch?v=Rvmvt7gscIM).

The brain’s network of neurons is very dynamic, capable of configuring itself into a vast number of distinct neural patterns. This flexibility forms the basis of neuroplasticity and, more broadly, the neurological foundations of learning. Each neuron can help perform multiple functions, but some are just more likely to contribute to specific acts. The idea that the same actions can be guided by different sets of neurons, even when performed repeatedly, is known as degeneracy.

To illustrate the complexity of our neural networks, she uses two helpful analogies. The ‘Meatloaf Brain’ functions by having all neurons connected to each other (Pinker, The Blank Slate). This analogy suggests that the brain functions as one big homogenous entity, without specialised modules, in which neural connections are continuously shaped by experience and learning. The ‘Pocketknife Brain’, on the other hand, has a number of tools, each with a number of functions. The possibilities are endless. A pocketknife with fourteen tools, each serving two functions, has 2¹⁴ possible functions (16,384). Each serving three functions is 3¹⁴ (4,782,969), 4¹⁴ takes it into the billions and so on. This Pocketknife vs. Meatloaf debate is synonymous with the Nativism vs. Empiricism debate. We now understand that the brain incorporates elements of both Pocketknife and Meatloaf brain, exhibiting both functional specialisation and significant plasticity and adaptation in response to learning and environment.

Barrett describes two processes – Tuning and Pruning –  that explain how neurons alter their connections, a developed explanation of Hebb’s original, ‘Neurons that fire together, wire together’. Tuning strengthens connections through frequent use, making future transmissions more frequent. Pruning, on the other hand, weakens and eventually eliminates less-used connections. One illustration of this I find particularly interesting. Newborns are much better at distinguishing sounds from other languages than adults because their brains haven’t been tuned and pruned towards a single language. This is partly why it is so much easier to learn languages as a baby. as well as highlighting the significance of early caregivers in the wiring of infants’ brains.

Lesson 4: The Brain is a Predictive Machine

As mentioned before, the brain doesn’t simply react to environmental changes, it predicts what’s most likely to occur so the body can be prepared and energy can be used efficiently. For instance, consider a soldier stationed in a foreign country, warned of nearby guerrilla attacks and having previously encountered similar conflicts. At night, he sees movement in the trees and decides to unload his gun, only to discover it was a local herder. How much blame should he bear? The last time he faced a similar situation, it involved an armed gang. In that context, being overly prepared for conflict saved his life, and so his brain learned to predict that in similar situations not hesitating may be the best choice for survival. Applying this concept to a more relevant context, consider an armed policeman searching for a black person while on the lookout for a criminal on the run. His previous experiences, combined with various sociocultural influences, mean subconsciously, his alertness is heightened as his brain anticipates a bigger threat. This preparation then increases the likelihood of a violent response, similar to the soldier in the woods.

 These issues are bigger than the actions of individual policemen or soldiers, and are deeply intertwined with wider sociocultural forces shaping how a brain may anticipate a situation.

To be energy efficient and survival-oriented, your neurons should be already firing in a pattern that will match the incoming sensory data. Interestingly, this means that sensory information is merely confirmation of predictions your brain has already made. For this reason, neuroscientists like to say that your conscious experience is a carefully controlled hallucination, which I think is fantastic. I’ll read ‘Being You’ by Anil Seth soon, which delves into this idea much more closely.

Our brains aren’t wired to accurately perceive the world, they’re wired to survive. Prediction and anticipation have been our evolutionary tools serving this purpose.

Importantly, this predictive mechanism is not beyond our control. We can change how we predict. For example, before public speaking your brain anticipates this physiologically – heart will race, palms will sweat etc. However, you can either interpret this physiology as anxiety and fear, or you can interpret it as energised determination. Studies have shown that the latter reinterpretation profoundly affects both the quality of the performance and the reported feeling of giving the performance. An organisation called Seeds for Change seeks to harness our capacity to shift predictions by putting children from conflicting territories (Palestine/Israel, Indians/Pakistanis) together to interact and discuss their feelings about the conflict, looking to challenge the predictive mechanisms that would typically generate hostility.

Philosophers have long debated the extent of our free will, or agency over our actions. While many actions are shaped by forces outside of our control, we do have the power to shift the context in which we predict, challenging the full determinist position. For this reason, I position myself as a 90% determinist (a semi-arbitrary number).

Lesson 5: The Brain Doesn’t Work Alone

Humans are inherently social creatures. Studies show that individuals live longer with close, supportive relationships and that loneliness can not only shorten lifespan but has all sorts of tangible physiological impacts such as higher stress levels, a weaker immune system, slower metabolism, worse sleep, etc. Barrett describes the enforced loneliness of solitary confinement in prison as ‘capital punishment in slow motion’.

We are the only species to regulate each other with words. Studies show that positive words has tangible physiological impacts – hearing, or even seeing, the words ‘I love you’ can increase heart rate, breathing, and metabolism. Reading ancient scriptures can have a similar effect, highlighting the power of words across time. Exposure to negative words also has tangible physical effects, and repeated exposure has fascinatingly showed a strong correlation with the chances of becoming ill, although the exact underlying mechanisms are unclear.

As she describes, other people are both highly beneficial for the brain, but can also cause the most harm. Tying this idea to the free speech debate is interesting. While most people believe in the importance of free speech, should the proven physical impacts of words on the mind and body be taken into account when determining the extent to which free speech should be protected?

The importance of sociability extends beyond changing states of mind, and to the very way we perceive reality.

For instance, money is often transferred via paper or invisible numbers over the internet. These have no inherent value beyond what we have collectively chosen to ascribe to them. Similarly, borders are arbitrary lines on the earth, existing only through the geopolitical meaning we agree to give them. We all live in a world of made-up social constructs that only exist through collective belief and the narratives we form from those beliefs.

Social reality and physical reality are intertwined. Studies show that wine tastes better than identical wine when people believe it’s more expensive, or coffee with labels like ‘ecofriendly’ tastes better than identical unlabelled coffee. This ties back into the predictive mechanisms of the brain. The social reality shapes our brain’s anticipation of external stimuli, which in turn shapes the experience of those external stimuli.

Lisa uses the 5 C’s to outline the main mechanisms by which this social reality is constructed: Creativity, Communication, Copying, Cooperation, and Compression. Creativity allows us to utilise our imagination and ascribe value and meaning to things beyond their physical value, such as borders and money. Communication refers to our ability to share these ideas and meanings through words, symbols, actions etc. Copying establishes these social realities as norms, particularly important in imparting these realities to children. Cooperation allows for the continuous integration of these social realities into physical reality.

The final C, Compression, is uniquely human. It refers to the ability to take numerous interpretations and types of information and distil them into one single, unified, and coherent explanation. Think of the detective who integrates witness statements from a number of people and forms them into one coherent understanding of the crime. Compression allows for the integration of the senses into an understanding of reality. Compression also makes it possible to think abstractly, allowing you to impose multiple functions onto the same physical object. Her example is a cup of wine that means one thing when a friend shouts ‘Congratulations!’ and another thing when a priest intones ‘Blood of Christ’.

Other animals also demonstrate these C’s. Crows creatively use twigs as tools, elephants communicate with low rumbles that travel for miles, whales copy each other’s songs, ants cooperate to find food and defend their nest. Bees abstractly encode both direction and distance into their wiggle bum dances, which are then interpreted by other bees. However, humans are the only species able to compress and abstract enough to create advanced social realities. For example, chimpanzees have social hierarchies, but these are usually determined by physical attributes, as opposed to our social hierarchies which are determined by a variety of abstract social reality constructs like elections and titles.*

Often, we mistake social realities for physical realities. Historically, racial categorisation has dominated social structures, with supposed variations in underlying genetics providing the basis for such distinctions. But skin tone is on a continuum, usually a result of evolutionary adaptations to specific environmental conditions. Despite this fact we’ve placed arbitrary boundaries between sets of skin tones, creating rigid racial categories that have fuelled some nasty tribalism. Social attitudes also affect the way we perceive ourselves, and may subsequently shape our neurological development towards whatever direction the attitude dictates. For example, studies show that women who are reminded of the stereotype that they are worse at math than male counterparts perform worse than women who weren’t reminded (see this other article I wrote on stereotype threat (https://in-psych.co.uk/2023/11/stereotype-threat/).

Our ability to construct social reality is a gift that can be harnessed for good or bad.

If we all collectively decided that the earth was flat and ignored all evidence to the contrary, that shared belief would become reality. Political leaders can shape social reality through rhetoric and propaganda. Kim Jong-Un has constructed a social reality in which he is the supreme and divine leader of the North Korean people, which is as real to them as anything else. Given the capacity for social reality to be wielded, critically engaging with the origins and impacts of constructed social realities is a valuable skill in identifying how social forces may be influencing our thoughts and behaviours. 

EDIT*

As I finish writing this, I came across two fascinating articles published on the same day which challenges the idea that these are uniquely human capabilities. One study focussing on chimps and the other on bees, found that both species are capable of ‘cumulative cultural evolution’, or social learning. This finding challenges the opinion that the ability to build upon knowledge and behaviours over generations through social interaction is unique to humans. This is the first experimental (not anecdotal) evidence for complex social learning in animals, which is awesome (van Leeuwen, 2024; Bridges, 2024)