With his leather jacket and shaggy hair, David Eagleman looks more like a musician than a neuroscientist. The New York Times best-selling author and director of the Laboratory for Perception and Action at the Baylor College of Medicine gave a fascinating overview of his studies into synesthesia and the place of the brain in our daily lives at this year’s South By South West event in Austin, Texas.

Going “under the hood”, Eagleman explained that there are trillions of neural connections being made to perform even the simplest of tasks. Very often when we have that “lightbulb” moment, our brain has actually been working on it for weeks with our subconscious mind running quietly in the background. In fact, a lot of what we see and believe is generated by parts of the brain that we have no access to. As Carl Jung said: “In each of us, there is someone that we do not know.”

For example, a study was done where men were shown pictures of women and asked to rate which of them were most attractive. They uniformly rated women whose pupils were dilated as being more attractive. They weren’t conscious of it, but dilated pupils are a sign of sexual excitement and the men were unconsciously drawn to these women.

Eagleman explained: “The conscious mind is like the CEO of a company. But underneath it there are thousands of employees with millions of functions. The CEO cannot possibly comprehend what is happening in every department — it would be overwhelming.”

This is why when you start paying too much attention to what you are doing, you start doing it badly. We need to automatise our behaviour to do things well, especially when it comes to playing sport or instruments. It seems “don’t overthink it” is the best advice your cricket coach could have given you.

Eagleman also points out that our brain constructs our reality, especially when it comes to vision. Vision is not like a camera — your brain is decoding the little bit of information it receives through your eyes and making assumptions about the rest to form a picture. You and a friend might agree you’re looking at the colour green, but there’s no way of knowing if the green you see is the same as the green he sees.

Then there is the phenomenon of synesthesia, which affects 4% of the population. Synesthetes experience a “blending” of their senses. This is caused by an unusually high level of cross-talking between different areas of the brain. For example, they might taste colours, see sounds or hear shapes.

People with synesthesia tend to have a better memory, because they have entire personalities attached to things. In one highly developed incidence, there was a man who saw each number with a colour, sound and shape (test if you’re synesthetic at Synesthete.org). Of course, “normal” brains also have lots of cross talk — we just aren’t aware of it. The numerous synesthetic metaphors we use, like “sharp cheese”, attest to this.

The human brain is not a single thing, says Eagleman, but is made up of “different populations battling it out to lead the whole country”. This is why we have the ability to feel conflicted. One part of your brain tells you to have that chocolate fudge cake because it’s delicious, while another part says it’s a bad idea for your waistline. This leads to us making a “Ulysses contract” with ourselves, where we do certain things to prevent certain behaviour (like not driving past the cupcake store).

The essence of our being is tied to our brain — you are your brain. We consist of this “alien computational material”, as Eagleman calls it. The frightening thing is what happens when this material is tampered with.

Charles Whitman, who killed sixteen people on a shooting rampage, was discovered to have had a brain tumour that led to his behavioural change. Then there was the case of the “sudden paedophile”, a normal heterosexual man who became sexually attracted to children after developing a frontal lobe tumour. The implications of this are massive, especially with regards to culpability and the legal system, and Eagleman has established Neulaw.org to examine the neural basis of morality and decision-making.

Just as Galileo discovered Earth was not at the centre of the universe, we need to understand that we are not at the centre of ourselves — our conscious mind is merely on the edges of a massive subconscious galaxy. Eagleman puts it more eloquently: “The expression should not be ‘know thyself’, but rather ‘know thyselves’. — Amanda Sevasti Whitehouse, TechCentral