Bruce Hood - The Self Illusion

Let’s consider some numbers again. With just 500 neurons, the number of possible different patterns of connections you could have exceeds the estimated total number of atoms in the observable universe. With billions of neurons, each with up to 10,000 connections, that suggests an almost infinite number of possible brain states. So figuring out what each pattern of electrical activity does is simply not feasible. The other problem is that no two brains are identical. Even identical clones of a very simple organism such as the water flea, when raised in the same environment have different patterns of neural connections. 7So any mapping of one brain is not going to apply directly to that of another.

A final nail in the coffin of predictable determinism is that thousands of different brain states can produce the same output. This is known in philosophy as ‘multiple realizability’, 8although I prefer the more familiar phrase, ‘There is more than one way to skin a cat’! What this means simply is that many different patterns of brain activity can produce the same thoughts and behaviours. There is no unique one-to-one mapping between the brain’s activities and the output of the individual. For example, scientists looked at a much simpler nervous system than the human brain – the gut of a lobster – and carefully recorded as many different patterns of activity of the nerves that control the digestive movements. They found that thousands of different patterns produced the same behaviour. 9For any individual cell, there were multiple patterns of activity with other connecting cells that produced the same output.

Multiple realizability is likely to be true for the human brain as well. In other words, our thoughts and behaviours are realized in multiple pathways of activity, which is a good thing. Remember that the neural networks are massively parallel. This means that the same neurons can be triggered by a variety of spreading activations. This parallel structure explains the speed, the complexity and ultimately the richness of mental life but it also means that you are never going to be able to map it out precisely – even within the same individual brain,

Despite the complexity of the mathematics of brain activity, many are still deeply unsatisfied with a materialist account of the mind, even if it is not predictable. We want to believe that we are more than fleshy computing devices that have evolved to replicate. We are not simply meat machines. Maybe there is some as yet undiscovered force at work? After all, we are continually reminded that most of the universe is made up of stuff that we know is there but cannot measure. How can scientists rule out the non-material explanation for the mind and free will if they themselves admit that they do not know everything?

The answer is they can’t. Science can only investigate and evaluate different models of the world and those models are only going to be approximations of the true state of the universe – which, frankly, we may never know. But science is continually moving forward and progressing by refining the models to better fit the evidence. And the evidence comes from our observations. However, sometimes observations are wrong. The big trouble with free will is that it just feels so real. All of us think that our thoughts happen in advance of what we do. Time moves forward and we experience that our thoughts cause actions. It turns out that this is wrong and we know this from the simple press of a button.

Living in the Past

Imagine I ask you to push a button whenever you feel like it. Just wait until you feel good and ready. In other words, the choice of when you want to do it is entirely up to you. After some time you make the decision that you are going to push the button, and low and behold you do so. What could be more obvious as an example of free will? Nothing – except that you have just experienced one of the most compelling and bizarre illusions of the human mind.

In the 1980s, Californian physiologist Benjamin Libet was working on the neural impulses that generate movements and motor acts. Prior to most voluntary motor acts such as pushing a button with a finger, there is a spike of neural activity in the brain’s motor cortex region that is responsible for producing the eventual movement of the finger. This is known as the ‘readiness potential’ (RP) and it is the forerunner to the cascade of brain activation that actually makes the finger move. Of course, in making a decision, we also experience a conscious intention or free will to initiate the act of pushing the button about a fifth of a second before we actually begin to press the button. But here’s the spooky thing. Libet demonstrated that there was a mismatch between when the readiness potential began and the point when the individual experienced the conscious intention to push the button. 10

By having adults watch a clock with a moving dot that made a full rotation every 2.65 seconds, Libet established that adults felt the urge to push the button a full half second after the readiness potential had already been triggered. In other words, the brain activity was already preparing to press the button before the subject was aware of their own conscious decision. This interval was at least twice as long as the time between consciously deciding to push the button and the actual movement of the finger. This means that when we think that we are consciously making a decision, it has already happened unconsciously. In effect, our consciousness is living in the past.

One might argue that half a second is hardly a long time but, more recently, researchers using brain imaging have been able to push this boundary back to seven seconds. 11They can predict on the basis of brain activity which of two buttons a subject will eventually press. This is shocking. As you can imagine, these sorts of findings create havoc for most people. How can we be so out of touch with our bodies? Do we have no conscious control? The whole point about voluntary acts is that we feel both the intention to act and the effort of our agency. We feel there is a moment in time when we have decided to do something, which is followed by the execution of the act. Brain science tells us that in these experiments, the feeling of intention occurs after the fact.

However, Libet’s findings do not mean that intention cannot precede actions. We can all plan for the future and it would be ludicrous to say otherwise. For example, in the morning I made the decision to check the mailbox, at the end of the drive, in the afternoon, and I did just that – I made a plan of action and then enacted it. There was no readiness potential in my brain to visit the mailbox. Likewise, many other actions happen without conscious deliberation and thank goodness for that. Imagine if you had to think about jamming on the brakes in a vehicle pile-up: you would be a goner. Whether it is long-term goals or automatic behaviours triggered by external events, in both instances the experience of intention happens either well in advance or sometimes not all. Our actions don’t always follow our intentions as in the Libet demonstration.

What Libet’s findings really show is that in a situation where we are asked to both initiate a willed action and monitor when we think we have initiated the action, the preparation for the movement happens well before we become aware of our intention. Most people find this amazing. However, neuroscientists are less impressed because they know the brain generates both the movement and conscious awareness. This makes impartiality and objective evaluation impossible. Another problem for interpreting the time-course of events is that the brain activation that generates conscious awareness is not a single point in time but rather is distributed. In other words, although we can suddenly become aware of an instance when we have made a decision, that process must have been building up for some period. It may feel like it happened spontaneously just before we moved our finger, but it didn’t. We just thought so. Spinoza figured this out 350 years ago.