Before writing this little story for the ABC this week I’d never really thought about free will. It never seemed like a topic that was going anywhere except round in circles. Now I’m a bit more interested. It seems as if the unconscious brain has already started the decision-making process before we think we’ve made a decision. In other words, the whole concept of “making a decision” could be an illusion.
The researchers behind this neat little piece of research warned me that people/journalists tend to “over-interpret” their findings: ie. get a bit over-excited. I’m not over-excited, but I am fascinated. What goes on in the brain before we realise we’re thinking? And can we be said to be in control of it?
Unconscious brain can predict decisions
Tuesday, 19 March 2013, ABC
Scientists have found that unconscious brain activity can predict a person’s decisions, seconds before they are even aware of having made a choice.
Dr John-Dylan Hayes from Berlin’s Charite- Universitätsmedizin and colleagues set out to understand what happens in a person’s brain when they make free decisions. There is considerable debate about the nature of unconscious processes and how they influence our thoughts and our behaviour, says Hayes.
“From an everyday person’s perspective you would think it’s obvious that there are all these unconscious processes going on,” he says. But in science there is a lot of sceptical debate about this. The problem is that unconscious processes are so difficult to nail down.”
Hayes and his team, including PhD candidate Chun Siong Soon, found a way to overcome this problem using functional magnetic imaging (fMRI), which measures how the brain uses oxygen when it becomes active. The findings appear in the latest issue of the Proceedings of the National Academy of Sciences.
In the study, 17 participants were shown sequences of single-digit numbers on a computer screen, one each second, while inside the MRI scanner. Whenever they felt like it, they could decide either to add or subtract the next two numbers. To measure exactly when the participants had made up their mind, the participants watched a computer screen that computer screen displayed not only numbers but also a sequence of letters – a technique pioneered in the early 1980s by researcher Benjamin Libet.
The participants were then asked to report which letter had been on the screen when they made up their mind. The fMRI data showed that before the participant was aware of making a decision to add or subtract the numbers, two regions of the brain involved in high-level control of behaviour started to encode the decision – a medial frontopolar region and an area straddling the precuneus and posterior cingulate. The prediction was made using sophisticated pattern classifier tools.
Predicting unconscious activity
“The predictions aren’t perfect, but we can predict considerably better than you would expect by chance”, says Soon.
The exact areas that became active also varied between participants, Hayes says. “What our data show is where there is information on average across subjects.”
The researchers recorded the brain activity up to four seconds before the participants thought they were making up their mind. However, because they calculated the predictability timing by averaging across subjects, they can’t currently say whether there was variation between individuals in how far in advance the brain activity began.
The latest findings follow two other studies from Hayes’ group that showed how simple choices to press one of two buttons could be predicted from brain activity. The new study shows that unconscious preparation also applies for high mental abilities, but Hayes also urges caution in interpreting the results.
“Our study shows that unconscious preparation in the brain definitely exists, but it doesn’t mean we can predict each and every choice. For example, in some cases something might let a person change their mind.” “Speculatively, one could think of our unconscious brain processes as giving a brief glimpse on the ‘dark unconscious matter’ of the brain,” Hayes says. “Of course, as in all experiments in the laboratory, our findings still have a long way to go before we can make claims about, say, important day-to-day decisions.”