I’ve cut brains in half, excised tumours – even removed entire lobes. The illusion of the self and free will survives it all

Written by Christian Jarrett on February 25, 2025. Posted in Current News

In 1921, the illusionist P T Selbit performed a magic trick that has since become a classic: he sawed his assistant in half. We’ve all seen it done dozens of times. We know it’s not real. Yet, we’re fooled every time. The deception appears impenetrable.

I can relate. As a brain surgeon, I’ve performed a similar trick. Don’t get me wrong, I’m not saying that brain surgery is a hoax. Our surgeries are not shams. But I’ve severed the brain in two and watched in amazement as my patients wake up feeling like their complete and undivided selves. When I first did this type of operation.

I had fantasies that they might suddenly refer to themselves as ‘we’ rather than ‘I’. Thankfully, this never occurred. In the case of the magician, the assistant’s wellbeing is real, and the cutting is the trick. For the brain surgeon, the cutting is the real part, while the patient’s sense of a unified self is the illusion.

The brain consists of two mirror hemispheres, left and right, that communicate with one another through a thick fibre bundle called the corpus callosum. Back in the 1940s, a neurosurgeon named William P van Wagenen developed an operation where he severed the corpus callosum as a treatment for epilepsy.

When his patients awoke, their seizures were improved. More remarkably, his patients were completely unaware that the two sides of their brains had been disconnected.

A few decades later, the neuropsychologists Roger Sperry and Michael Gazzaniga studied more of these so-called split-brain patients and discovered that each half of the brain processed information independently. Each could make its own decisions and control its own behaviours. In a sense, the surgery had created two separate selves. In some of these patients, one side of their body (controlled by one hemisphere) would do one thing, while the other half (controlled by the other hemisphere) would do the opposite. For example, one hand would button their shirt while the other hand would unbutton it.

So why didn’t these split-brain patients, post-surgery, feel like they had two selves? The answer is that their brains fooled them into thinking that only one self existed and that it was in charge. When one of their hands did something unexpected, they made up a story to explain why. I changed my mind. I didn’t like the way that shirt looked.

These stories or confabulations show the power of the illusion of selfhood – a feeling that evolutionary psychologists believe evolved because it is adaptively useful. What better way to ensure that the physical package carrying and protecting the information in our DNA – namely, our bodies – survives long enough to pass on that code to the next generation? The illusion of the self makes us feel unique and provides us with a goal-oriented purpose to our lives.

Time and again, I’ve seen the resilience of the selfhood illusion in my surgical work. Sometimes, when a patient has a big tumour, or seizures arising from a very large cluster of abnormal neurons, we remove an entire lobe of the brain. I’ve removed a frontal lobe, a parietal lobe, an occipital lobe, and a temporal lobe, on the right as well as the left. Performing such a surgery can be disconcerting, as it often feels more like a violation than a remedy. These surgeries can cause subtle alterations in memory or personality. Still, in every case, my patients have emerged feeling whole, as if none of them was missing.

More than once, I’ve even removed an entire half of a brain, as a treatment for epilepsy in young children. Each time, I knew intellectually that the surgery should help, and took comfort knowing that the healthy remaining brain would have already begun compensating for its diseased partner. But, emotionally, it was hard not to imagine how devastating such radical surgery would be to the patient. Yet, despite what felt like my desecration of their brains, these patients too never felt that their identity and sense of self had diminished.

If our sense of a coherent, unified self is an illusion, as brain surgery so convincingly reveals, what does this mean for our innate and powerful intuition that ‘we’ are in control of our actions? The idea that we have free will is fundamental to most of the world’s religions and our legal systems. Yet, simply put: how can I be in charge if there is no I?

Brain surgery provides the answer to this question as well: free will is also an illusion.

To find the source of a patient’s epilepsy, surgeons sometimes insert recording electrodes into the parts of the brain that are involved in planning movements (called the supplementary motor areas). When they do this, they can listen to the activity of individual neurons as the patient performs certain actions. For instance, if we ask these patients to move a finger, or repeat a phrase, and an electrode is in just the right location, we can observe the neurons firing in real time and watch as the brain’s machinery runs the algorithm that generates the behaviour.

Now, if we ask the patient to take note of the moment they first decide to move, or to speak, let’s say by looking at the second hand of a clock, we find that the neurons start to fire half a second earlier. A similar finding was reported in the 1980s by the neuroscientist Benjamin Libet, who first attempted similar experiments using less sensitive scalp electrodes.

The brain and its neurons activate before the individual decides to act. In fact, more recent studies by the neurosurgeons Itzhak Fried and Ziv Williams confirm that it’s even possible to use brain cell recordings to predict what someone will say before they say it. This creates some spooky possibilities. With a little bit of engineering, in theory, we could create a machine that mimics your speech and anticipates it. If you and the machine were sitting next to each other in the same room, the mechanical Houdini would blurt out everything you said a fraction of a second before the words left your mouth.

There is also a physical aspect to selfhood that parallels our subjective idea of being a self. It derives from our unique point of view in space over time. As biological organisms, we are bags of chemicals housed in a protective coating. If you’re a bacterium, it’s a cell wall. If you’re a human, it’s skin. This membrane separates self from other. We also possess a singular point of view: a focal point where all our senses come together.

There are places in the brain where this multisensory integration occurs, mostly in the parietal lobe. If a neurosurgeon stimulates these areas with an electrode in an awake patient in the operating room, we can cause the sense of self to dissolve. Patients have an out-of-body experience. When we stimulate other nearby neural areas, the patient’s sense of free will is altered.

For example, they might feel an overwhelming desire to move. When the surgeon stimulates the planning areas of the brain, the same experience occurs. Not surprisingly, the planning areas and the multisensory integration areas of the brain are highly interconnected. It seems that there is a network of brain modules that support the illusion of self and the illusion of free will. The two phenomena are biologically interconnected.

All this evidence from neuroscience and neurosurgery makes one thing abundantly clear: our everyday feelings of selfhood and free will do not align with the experimental facts. I’ve thought about the implications of this for decades and I’ve come to realise that the only way forward is to accept the unnerving counterintuitive conclusion that the mind and the self do not physically exist. Which is not to say that they don’t exist at all. They are fictional mental constructs, akin to the concepts of love, justice or freedom. As a brain surgeon, this perspective is liberating. When I operate, I am not afraid of destroying someone’s identity.

I can focus entirely on preserving function, such as the ability to see, to walk, to hear or to speak, while knowing the powerful illusion of selfhood is likely to emerge undimmed.

While you may think that this perspective leads to a depressing form of existential nihilism, for me it’s just the opposite. The sheer number of sequential random events required to create a human consciousness may just be the greatest miracle in the known cosmos.

The improbability of our existence in a deterministic universe far exceeds the ease with which an all-powerful being could create us. In everyday life, the illusory nature of the self and free will is irrelevant because we can’t lift the veil to see the world any other way (certain meditation techniques that can lead to a dissolution of the sense of self might be the only exception).

The next time you watch a talented magician performing a mind-bending illusion, remember that the greatest magician of them all is your own brain. It performs its tricks in the theatre of your mind and, like any good magician, the deception is impenetrable.

See more here Psyche.com

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