Is this thought “mine” or “yours”? New study finds our brains can be trained to distinguish between the two
A new study by the Centre’s Cognition and Computational Psychiatry team has found that our brains can be trained to learn whether a thought is “mine” or “yours”. This means that the ability to put yourself into someone else’s shoes is flexible, rather than fixed. It also shows how our subjective sense of ‘Self’ might adapt to our social environment. Their new findings have been published in Nature Communications: Social training reconfigures prediction errors to shape Self-Other boundaries.
In order to meaningfully put yourself into someone else’s shoes, your brain needs to distinguish between your actual thoughts, and what you expect to be the other person’s thoughts. In a previous study, the team showed that when you think about someone else’s beliefs, your brain represents the beliefs of ‘Self’ and ‘Other’ in distinct pathways in the brain. If your brain represents these beliefs with very distinct pathways (i.e. there is little overlap between Self and Other beliefs), then you’ll be better at discriminating your own beliefs from the other person’s.
In this new study, the researchers wanted to see whether the degree of overlap of Self and Other beliefs in the brain could change with training. 40 participants were therefore asked to play a computer game, where they observed a series of coin flips. The coin was biased, and the amount of bias of the coin changed slowly throughout the task. For example, at the beginning of the game, the coin might be biased to show up ‘heads’, but by the end it might be more likely to show up ‘tails’. The participants had to keep track of the bias of the coin as it changed. Additionally, each participant was partnered with a second participant, who played the game at the same time. However, the partner could not see all of the coin flips, and was also shown some additional misleading coin-flips. This meant that the partner always had a false belief about the bias of the coin. The participants were also asked to keep track of their partner’s false belief, as it slowly changed throughout the game.
A mathematical model, called a predictive processing model, was then used to describe what was going on in a participant’s mind, as they played the game. Firstly, the model described how participants changed their own belief every time they saw a coin flip. Secondly, it described how they changed their estimate of their partner’s belief, every time the partner saw a coin flip. The model works by calculating ‘predictions’ and ‘prediction errors’. For example, if the participant predicts that there is a 90% chance the next coin flip will be heads, but then the coin comes up tails, the participant will be surprised. In the language of ‘predictive processing’, we can say that the participant experienced a large ‘prediction error’. The model uses this prediction error to improve the participant’s prediction for the next coin flip.
Every participant played the game twice. In the first game, they played with a partner who saw a lot of the same coin flips as them. In the second game, they played with a different partner who mostly saw different coin flips to them. The next day, the participants were brought back and asked to play the game again, with both partners, but this time there was no difference between the two games (i.e. both partners saw the same amount of coin flips that matched what the participant saw). The authors could then see whether participants had learned anything, on the first day, about the relationship between their own thoughts and the partner’s thoughts, that would affect their ability to distinguish between Self and Other, on the second day.
Remarkably, on the second day, the study found that participants struggled to distinguish between their own beliefs and the first partner’s beliefs (with whom they had seen mostly the same coin flips on day 1). However, participants found it easy to distinguish between their own beliefs and the second partner’s beliefs (with whom they had mostly seen differently coin flips on day 1).
The authors also scanned the participants’ brains using functional magnetic resonance imaging (fMRI). When a person experiences a prediction error, it’s because of a particular pattern of activity in their brain. In this study, the scans revealed that the brain activity seen when a participant experienced a prediction error had merged with the activity seen when estimating the prediction errors of their first partner. However, this activity had become distinct from that of the second partner.
This reveals new, exciting information about prediction errors, which are fundamental learning signals in the brain. Not only do they contain information about the subjective sense of Self, but also the way they are represented in the brain can change with experience.
Lead author, Sam Ereira, said: