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What causes us to think and act the way we do?

This is the grand-daddy of all questions, isn't it?

What causes us to think and act the way we do?

If we know, we can understand ourselves deeply, and shape our thoughts and actions to be better. 

The good news: there is a good answer for this which we hope more people will come to understand. But it is also precisely because we have  sense of how people think and act, that we know most readers don't want a good answer, they want a short one, preferably no more than 30 seconds of reading time. 

But consider how complex and complicated people are. At times you do something even though you clearly know it is not good for you. Yet at other times, you surprised yourself by doing something you thought you couldn't. Sometimes as a neutral third party, it is so obvious watching 2 people arguing that both have some parts right and some parts wrong. Yet when we are the ones in the argument, it' always the other party that's this terrible person who has no logic or no feelings and why can't they see where they are wrong?

Moreover, we are tremendously malleable and adaptable - we are always changing; in fact, your brain is changing right now as you read this. Yet at the same time, we are also deeply wired by accumulated experiences passed down evolutionarily, culturally, and through genetics. No matter what race or age you are, a loud "BANG!!!!" beside your ear causes you to be frightened, and we can never grow out of that. Or even if I proclaim beforehand that this is just to provoke you, please don't pay any attention to it - you can't. When I write that "everyone who believes in religion is just a mindless sheep, which is why 80% of all believers follow the religion of their parents", this triggers an emotional response in you. You might already be formulating a belief about me right now, even if you don't know who I am. You can't stop yourself from having this natural response, you can only control how you choose to react thereafter. 


|||   Thoughts and behaviour are affected by a wide range of influences, from what happened millions of years ago in the first cycles of evolution, to what happened 3 milliseconds ago - which neurons transmitted which neurotransmitters in your brain.

Let's take a look at an example:


It's pitch-dark, and you're walking through an empty park to get home.

And as you turn a blind corner, you suddenly see a guy coming towards you. He's holding something. 

selfie stick shotgun.jpg

In reality, the person is carrying selfie stick, shooting a video of himself. But in the darkness, it looks threatening. It looks like a gun. 

Here's where we typically ask the question: What are you thinking at this moment? How would you react? 

And this is where we get the wrong answer.


We believe that thoughts and action for singular reasons. Except they don't. 

Consider the table below. Would your thoughts and reactions be different if you experienced something in green as compared in red? Would you thoughts and reactions be different if any of these influences changed?

(click to expand)

different factors part 1.png
different factors part 2.png

If you had experienced more of the examples in red, you are more likely to feel that the man carrying the object is dangerous, and react fearfully or even violently to protect yourself. In contrast, if you experienced more of the influences in green, you are less likely to feel threatened. 

This brings us to the crux of this crucial chapter:

||| Thoughts and behaviour do not occur for one reason


There are many fields of science - neurobiology, endocrinology, genetics, behavioural science, sociology, ethology, and evolutionary psychology - that all do an excellent job in explaining how a change in one aspect of their field makes us a little different. Nonetheless, these divisions in science are all artificially created. The true picture lies in the interplay between all these fields. 


Each branch of science is like an ingredient that contributes to making a cake - there's flour, eggs, sugar, baking powder, cream, colouring and more. Each ingredient is important, and if one ingredient is missing, the cake turns out different. But when we look at the final product, the cake itself, can you distinguish between which part is egg and which part is flour? You can't - because the ingredients have mixed and reacted with one another to produce an overall cake. 


Here, we introduce a terrific frame created by Stanford's Robert Sapolsky, that maps out an overall picture of why a thought or action occurred. When we ask why a thought or behaviour occurred, what we're really asking is a series of questions:

sapolsky 1.png
sapolsky 2.png

Each question in this series is important in and by itself, but also in combination with one another.

Let's take a look!


1 second before

What goes on in our Brains?

The Amygdala

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Frontal Cortex

Frontal Cortex.jpg



seconds to Minutes before

environmental Stimulus we encounter

This sounds fairly obvious. You see a gun, you feel frightened; you see a math question, you feel frightened or joyful (depending on which way you swing); you see a picture of your favourite topic, you get excited; you pass a familiar place and past memories trigger.


But what we don't realise, by definition, is the entire world of subliminal and subconscious effects, which influences are in extensive ways. The picture above provides just a small sample of a large number of examples:

And this list goes on and on. We are constantly swayed and influenced by all sorts of stimuli, some seemingly irrelevant, some insignificant, some unexpected, often in ways we are unconscious of, causing us to think and act differently. In fact, this has birthed an entire field of behavioural economics - we are far less rational and autonomous decision makers than we like to think. As you explore more on this site, you will find more examples of the subconscious effects on our thoughts and actions. 

Hours to days before


Earlier we covered neurotransmitters like dopamine, which act as a currency for our neurons to talk to one another. Hormones are another group of chemicals produced so that different regions can communicate with one another. Unlike neurotransmitters, they come in effect slower, over hours instead of seconds. They also affect regions outside of our brains. 

testosterone monks hormones.jpg

What are some of the effects of hormones? Broadly, hormones make us more sensitive to environmental stimuli. They also cause an exaggeration of our existing tendencies. Let's take a look at 2 major examples: 

Testosterone: When we think of testosterone, we think of younger males getting aggressive and rowdy, starting fights, doing all sorts of silly actions.

But that's not what testosterone does. Take a baboon and load him up with testosterone. What we notice is that the monkey goes full-out beating up other smaller monkeys lower than him in the hierarchy. But he never touches a monkey higher up in the hierarchy. Testosterone doesn't create new anger or aggression. Instead, it amplifies existing aggression and lowers the threshold for it to trigger. 

But we can push this further. Terrific work from John Wingfield of UC Davis gave us the "Challenge Hypothesis" - testosterone kicks in to help maintain our status when we are being challenged. In the case of the baboon above, maintaining status is through violence. But what if it were humans, and what if status was defined differently? Experimenters got a group of folks to play an economic game, where the winner was the most generous in sharing economic rewards. All participants were loaded with testosterone beforehand. And what happens? Everyone competed with one another to see who could be more generous. Hence, we have the quote from Sapolsky above:

Testosterone is not about aggression, it's about maintaining status; just that quite often, status can be maintained through aggression. When we change what defines status, we change how testosterone affects us. 


A second example, Oxytocin: Oxytocin is commonly referred to as the love hormone. When oxytocin is secreted, it makes us more trusting, more cooperative, more generous, better listeners, more loving, show more care. When you come home after a bad work day, and you get comfort from hugging your spouse or your kids or your friends or your dog, oxytocin is secreted making you feel better.

And we can immediately consider implications: if you had to present the same exact idea to the boss, when do you think there is a higher likelihood he/she would say yes? In the middle of a normal work day? Or at the start of a workday after the boss had enjoyed a leisurely breakfast with his family, when his toddler calls him "dad" for the first time while his pet dog licks him like there is no tomorrow? 

Amazingly, oxytocin also counteracts the negative effects of stress. Not only does it provide emotional uplifting, but it also prevents cell damage and helps maintain our health.  

But once again, we can push this further. 2 studies by Carsten de Dreu of the University of Amsterdam provides a deeper level of understanding. 

When participants with high levels of oxytocin engaged in a simple economic game, they were expectedly extra-generous to people who were on their team. However,  oxytocin also made participants more likely to stab those who were not on their team in the back.

In a second experiment - the classic trolley problem - participants had to decide whether they would sacrifice one person to save the lives of 5 people. Participants with elevated levels of oxytocin were far less likely to sacrifice a hypothetical subject with a Dutch name (remember, this was conducted in the Netherlands), and far more likely to sacrifice a hypothetical subject with a German or Middle Eastern name.  In other words, oxytocin enhances pro-social behaviour but only within people whom we consider to be like us, in our "in" group. Oxytocin makes us more anti-social towards people who are unlike us, in our "out" groups. 

So our brains are constantly being marinated in a concoction of different hormones. These hormones could have been secreted hours or even days before, which then continue to affect our thoughts and behaviour. Ever recall a day when you were very angry at the start, and it spoiled the rest of the day?

Weeks to months before


experiences Changes our brains

Our brains are incredibly plastic - constantly changing as we go through new experiences. 


If you think about it, this has to be the case. It is precisely because our brains can change that we can continue to learn new skills and new knowledge throughout our lifetimes (in fact, your brain is changing right now, albeit very slightly, as you read this). And as it turns out, this change can be quite drastic.


What are some examples?

  • A major and positive discovery in neuroscience is neurogenesis: the growth of new neurons in our brains. We used to think that our brains peaked at a certain age, and then continually declined as we grew older. Neurogenesis proves this is not quite the case - some neurons die off with time, but we also develop new ones, especially when we learn, try new things, and stay active.

  • Stress causes our amygdala to not only become more active but physically bigger. We covered the effects of the amygdala earlier on. A hyperactive amygdala causes an individual to exhibit more anxiety, more anger, more suspicion of others, greater production of stress hormones, generally a more difficult and unhappy life. A great example of this are those who suffer from PTSD - the major trauma causes so much stress it changes a person in a major way

  • Stress affects another part of our brain, the hippocampus. What does the hippocampus do? It's responsible for learning and new memories. Unsurprisingly, this is the also the brain region where neurogenesis dominantly takes place. In an interesting study, London cab drivers saw an enlarging of the hippocampus as they had to learn and memorise the complicated road network of London. Prolonged stress leads to the opposite - the hippocampus trophies and neurogenesis reduces. 

  • Final point on neuroplasticity in this short summary - neuroplasticity is values free. Whatever we choose to do more of, our brains change so that we become more comfortable and more inclined to be able to repeat it. If you're constantly stressed, your brain makes it easier for you to feel stressed. If you constantly read about astrophysics, your brain becomes better at grasping new concepts about space and time.

    Conversely, whatever we do less of, our brains increasingly become less familiar and able to do it. You might have been a great violinist when you were young, but you lose touch if you stop playing. You might have aced an exam on European history, but if never revisited it, you would start forgetting some of the content. 


  • Read more about neuroplasticity here. 

Back to Adolescence

Immature pre-frontal cortex coupled with mature dopamine and hormonal systems

Our teenage years tend to an influential time in shaping us. This is the period when we start to pursue things more independently, ponder about some of the bigger questions in life, and develop our beliefs and identity. 

But there are 2 major biological features of the teenage brain, which contributes to great variance in teenage experience, which consequently influences the adults we become, and the type of thought and action we are more likely to take. 


The first is that chemical systems like dopamine and testosterone are full-blown by our teenage years. 

We have covered what these neurochemicals do earlier on: Dopamine is about the pursuit of anticipated rewards, while testosterone is about fighting to maintain status. And this explains why in our teenage years, we are thrill-seekers, we pursue the sensation of novelty, we are particularly bothered by how people view us.


The second biological feature is a bit more surprising. Our frontal cortex is still developing at this age


Look at the top left-hand corner of the picture above. Purple indicates regions of the brain are fully mature - While the middle and back regions of our brains mature earlier, the frontal region of our brain remains green or light blue during adolescence. 

In fact, our frontal cortex only fully matures around age 25


This has 2 major effects. The first is that we lack a mature and influential frontal cortex that provides more accurate analyses, delay gratification, and to control impulses. With a more mature frontal cortex, we are able to discern that people can be impressed in many ways -  not just being a jock, but as a knowledgeable geek, or an empathetic and caring friend. Or that we don't really need to impress everyone in life.

The second effect is deeper and more meaningful. If the frontal cortex only matures at age 25, it is by definition the
most affected by the environment and the least affected by genes. This sounds surprising but it makes complete evolutionary sense. For most of us, social interactions are the most difficult challenges in life. No gene can code for the variation of when we should lie, how much to lie. or to not lie but be extremely thrifty with information. No gene can code for why it is ok to pay a stranger to cook for us or to transport us from one place to another, but it is not ok to pay your relatives or your friends to do the same thing. No gene can code for context, why sometimes we use the same word - "no", when someone praises us, or when someone accuses us. 


With a strong dopaminergic system and high quantity of hormones due to puberty, while at the same time sporting a frontal cortex that is not yet mature, the environment plays a critical role in shaping who we become. A teenager surrounded by people who prey on the need for acceptance and status might be pressured into joining a cult or a gang.  On the other hands, a teenager surrounded by people who believe and support him/her could develop true self-confidence to take in criticism and constantly improve. 


A different environment, a different adolescence, a different adult - with different thoughts and actions. 

Back to Childhood and Fetal Life

Epigenetics - When we were young, so young

There are 3 big influences of how thoughts and actions during our early years.


Let's start with something slightly more technical.


What's the difference between DNA and genes? We seem to use the 2 interchangeably, but they are different.

genes vs dna 2.jpg

Put simply, our DNA is a unique code of about 3.5 billion base pairs of nucleotides molecules, which we inherit from our parents. Genes are specific portions of our DNA that codes for a protein that performs a specific function.

|||  Only a very small percentage of DNA (~2%) codes for genes.


What does the non-gene coding portion of our DNA do? One important function is the expression of genes.


|||  The non-coding DNA acts as switches, which are turned on and off depending on interaction with the environment. In some environments, certain genes never get expressed; on the hand some genes are only expression in a certain environment.  


This is a process we call epigenetics. And as a fetus or a young child, our bodies and brains are still developing. And these epigenetic effects can cause changes to what genes we express, sometimes fairly permanently.


A second major influence is the period of pre-natal life*. We often assume that the environment begins at birth. This is false, and our prenatal environment can cause major changes to the person that we become.

For example, if mom was an alcoholic (we're not talking about the occasional glass of wine, but someone who turns to the bottle regularly), this causes epigenetic changes to the fetus' brain. In particular, the baby grows up with a thinner prefrontal cortex (we covered this - the rational part of our brains). Similarly, a highly stressed mother might cause epigenetic changes to the fetus, causing him/her (or if you prefer, it) to develop an endocrine (or hormonal) system that is hyper-reactive to stress hormones.  

*we're working on a pre-natal segment, so do check back to this website!


There is also the regretful case of the Dutch Hunger Winter:

dutch hunger winter.jpg

In 1944, with World War 2 still going on, the Netherlands faced a terrible famine. There was so little food that the Dutch developed a thrifty metabolism - the bodies stored all meagre amount of food it takes in. This included pregnant women, and what it meant was that the babies of these mothers were born severely malnourished, as most of the food consumed by mom was stored by her own body.


Since food was so scarce for these babies, they developed their own version of thrifty metabolism.


The famine was over very shortly after winter, with the Allies driving out the Nazis, and food became available again. But this thrifty metabolism was already coded in these newborns - so they went on through their lives to store food at a much higher rate than normal people. What this led to was an obesity rate that was about 19 times higher than normal, even though these folks did not eat more than others.

Moreover, when these female kids grew up to be mothers themselves, the thrifty metabolism carried over to a third generation. Again, fewer nutrients than normal went to their fetus during pregnancy, which led to the next generation again developing this thrifty metabolism. The experience of one generation carried over to several subsequent generations. 


Read more about the Dutch Hunger Winter here. 


Finally, we move on to our third major influence, behaviouralism. As young children, our brains are naturally not yet developed to consider whether something is really or wrong, of unique identity, etc. This is basically a period where we copy what adults are doing, and we learn what is right or wrong by observing whether the adults would reward or punish us for certain actions. So our interactions during this period, and what we got praised or punished for shapes us while we are still unable to really think for ourselves. 

When sperm met egg

The start of our life - a fertilised egg, when our genes are coded


We touched on DNA and genes in the previous section.  All of us inherited our complete chain of DNA from our parents, about 3.5 billion base pairs long. But only about 2% of our DNA codes for genes (genes codes for specific proteins, each responsible for a particular action). In fact, just 40-50 years ago, we thought the human being had about 100,000 genes. This estimate goes down every year, and we now know we only have about 20,000 genes.

More importantly, there is the role played by non-coding DNA, which upon interaction with the environment, then expresses or not express certain genes. 

genes examples.png

The table above provides us with some examples.


In particular, you might be familiar with MAO-alpha, highlighted in red, popularly referred to as the "warrior gene". What MAO-alpha does is code for an enzyme that impacts several important neurotransmitters. This, ostensibly, leads to greater violence: there are reports in the Netherlands, Finland, and the USA of families that commit gruesome, violent acts of crime.


These families are united by one unique feature: the MAO-alpha gene. 

Until we look a little bit closer.

While there is a higher incidence of people committing violent crimes that possess the MAO-alpha gene,
there are also those who possess the same gene and get through life just fine. So what gives? It turns out that it is not the MAO-alpha gene that triggers violence per se. It is the MAO-alpha gene combined with an abusive childhood that creates an angry, anti-social, aggressive individual capable of extreme violence.

In other words,
the same gene acts differently in different environments


This is the essence of this mini-chapter. By definition, genes must affect our behaviour, because it is a gene that codes for every neurotransmitter, hormone, receptor, cell etc. And even though all of us share the same types of genes, each gene has many different versions, which goes some way in explaining individual differences between us. 


But the effects of genes are tremendously context-dependent. It is not meaningful to simply ask what a gene does. A more useful examination would be what a gene does in a certain environment, and/or what other genes or networks of genes are expressed at the same time.  

And this is particularly important because the human being has thrived in the widest variety of environments: living in the deserts and living in the Arctic, in mega-cities to tiny farms, in capitalism or communism, with loving or absent parents, with encouraging or judgemental teachers, growing up reading or playing sports or learning an instrument or speaking one of the so many languages around the world. Our environments are so remarkably diverse, yet the human being has always found a way to cope. 

(Genes vs environment is a classic debate that has gone on forever. We tackle this topic at our Nature vs Nurture section - look out for new updates!)

Decades to centuries before

How did culture shape the social environment and habits where the person is living

I'll spend the least amount of time on the effects of culture because this is the area most of us will be most familiar with - just look around at our daily lives.

Some quick examples:

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Individualism vs collectivism: This should be familiar to most of us, especially if you know folks from both Eastern (collectivism) and Western (individualism) societies. 

hen asked in free recall, Americans are more likely than East Asians to remember times in which they influenced someone; conversely, East Asians are more likely to remember times when someone influenced them. Force Americans to elaborate on a time when someone influenced them, or force East Asians to share an account of them influencing another, and both secrete stress hormones having to recount this discomfiting event.

Another example: dopamine systems activate in European Americans when looking at excited facial expressions; in Chinese, when looking at calm expressions.

Choice: The psychologist Sheena Iyengar performed a series of studies on people's preference about choice. They gathered Anglo-American and Asian-American kids aged between 7-9, and divided them into 3 groups to work on some puzzles:

- Group 1 were told that they could pick whatever puzzles they like

- Group 2 were greeted by a teacher, who told them which puzzles to work on.

- Group 3 were told that puzzles they should work on have already been picked by their mothers. 

This seemingly small difference of who decides which puzzles to work on, leads to a major difference in performance and satisfaction:

- Anglo-American kids did two and a half times more anagrams when they got to choose them, as compared to when it was chosen for them by either the teacher or their mother.

- Asian-American children performed best when they believed their mothers had made the choice, second-best when they chose for themselves, and least well when it had been chosen by the teacher.

The difference is that with Asian-Americans, choice is not just about asserting their own individuality, but a way to uphold community and harmony by taking into account the views of people whom they trusted and respected. 

technology then and now.jpg

Technology: Not much elaboration required here either, surely? Just consider life today compared to 25 years ago when there was no high-speed internet, no laptops, no-email, no online-shopping, no handphones, no Fitbits, no tablets, no YouTube or Instagram or online courses, no Zoom or video-conferencing. 

Consider how hard it would be to compare your culture with another. To see another part of the world. And to regularly communicate with folks across oceans. Technology allows us to physically and virtually get access to things with much more ease and much quicker. 

Religion by geography.gif


"How thoughtful of God to arrange matters so that, wherever you happen to be born, the local religion always turns out to be the true one."

Regardless of whether you agree or disagree with his stance, the religious sceptic Richard Dawkins accurately highlights an important point about religion. Even though religion seems so important - what you believe in and what happens to you after death - the choice of religion rarely lies with the individual but is more greatly influenced by geography and family. An estimated 80% of people simply follow the religion of their parents. 

Roles and Responsibilities: The Japanese education system tends to leave foreign teachers baffled. On one hand, the Japanese system if very rule-based - it's not just that the kids have to learn new knowledge, but they have to learn it the right way. So there is very little room for creativity or spontaneity in classes, teachers have a very strict process to adhere to. I happen to have few friends who went to Japan to teach, and they moan about this continually. You can follow this account of a Brit who taught English in Japan for a couple of years.

Yet in another aspect of life, Japanese kids are also incredibly independent. I once flew a domestic flight in Japan, and beside me was a young girl who can't have been more than 5 or 6 - she needed a special seat because she was too small for the normal one! And everything about her demeanour showed that this is unlikely to be her first time - she knew exactly to expect, including the knowledge that flight refreshments included her favourite can of carrot juice. Check out this video below:

So different cultures and the era that we live in (hence the level of technological progress and current global climate) all systematically shape how we live our lives. Culture is the coloured lens that is placed on us from the very moment of birth, influencing how our parents are likely to react to us, the colour of the first outfit we put on,  whether we are a sinner or a reincarnated being, what happens to us after death, when we first learn independence, how we choose, and what identities we form. Our brains, genes, and mindsets are continually moulded by the habits and lifestyles of those around us. 

Millions of years back

How did that behaviour evolve? 


Here we come to our final consideration of why a thought or behaviour has taken place - evolution - generation after generation of evolution, over millions of years.  

2 quick points to note: 

1) Evolution is NOT survival of the fittest, but rather which species survived and passed on copies of their genes to the next generation. Take a look at the example above. If we look at fossils, about 14 million years ago, giraffes' necks were as long as they are today. However, as with all species, there were variations. Some giraffes had slightly longer necks than others. Those with longer necks were more likely to survive because they could get more food. As more long-necked giraffes survived and produced than short-neck giraffes, the population of giraffes over time became more and more likely to have longer necks. 

(What happens when evolution is compressed into a very short time-line? Check out the fascinating examples of Mickey Mouse and of domesticated foxes)


2) Similarly, this is the case for humans. Some of our ancestors had certain characteristics which made them more likely to survive and reproduce than others. What are some of these characteristics?

Fear kicking in very quickly. This brings us back to our first very section on the Amygdala and the Amygdala hijack - fear occurs to us very quickly and powerfully, causing us to take immediate action to protect ourselves. Imagine ancestors of ours who were fearless or whose fear kicked in very slowly. By the time they felt fear and took action, they would have been mauled to death by predators - no copies of genes passed down. 


Information filtering and categorisation. We encounter so much stimulus in life - everything you see or hear of touch. So our brains evolved to deal with all incoming information quickly and efficiently, but at the cost of accuracy:

  • Information is filtered out - remember the horrific incident of planes crashing into the twin towers during 9/11? You must have seen pictures and videos, but do you remember if there were clouds in the sky? You don't. Your mind automatically filtered it out without your instruction. 

  • Information is quickly categorised - this person is from a certain racial group; all art students can't count; all science students can't draw...

  • We make many decisions with heuristics, simple indicators that allow us to come to a reasonable decision most of the time, but becomes increasingly inaccurate as decisions become more complex. 

Read more about 5 major characteristics of human behaviour here.

Body language. Verbal or written language was a very recent advancement. For most of our history, just like animals (a bear standing on its hind feet, a snake coiling up, dogs greeting one another) body language was the main means for us to communicate what we thought or felt. Which also explains why some body language is universal, regardless of culture or race. Here's a more entertaining take by Joe Navarro, author of several books on body language such as: "The Dictionary of Body Language", "What every Body is saying", "Louder than Words". 

Morals and values. It's also interesting to note that many things we assume to be unique to humans are actually not so unique. Even (biologically) simpler animals like stickleback fish and vampire bats engage in game theory; primates understand and exploit information asymmetry. And as you would see in the video below, monkeys perfectly comprehend and protests against values like unfairness - something you and I would similar feel aggrieved about. We didn't just learn about these things in schools and books, but part of what is right or wrong is passed down through ancient wiring from simpler to more complex animals, to our ancestors and then to us, over generations of evolution. 

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