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Can 'rock, paper, scissors' help us understand delusions in schizophrenia?

By using a computerised game of ‘Rock, Paper, Scissors’, researchers at King’s College London’s Institute of Psychiatry (IoP) are attempting to understand the mechanism behind the formation of delusions in patients with schizophrenia.

The study, from the Cognition, Schizophrenia and Imaging Lab at the IoP at King’s is published this month in Psychological Medicine. The study shows that, unlike healthy people, patients with schizophrenia are unable to use their experience to guide their decision making, but despite this, they are over confident in their decisions, leading to an increased likelihood of maintaining erroneous beliefs, such as paranoid delusions.

People with schizophrenia frequently experience deeply held delusional beliefs which are at odds with their cultural context, impossible to challenge and are one of the most distressing symptoms of their illness. These beliefs are derived from information collected through interactions and experiences with the world, but for some reason, these experiences are interpreted and integrated into a belief system which is contrary to prevailing norms and even in the presence of clear contradictory evidence, they are unshakeable.

To date, there has been little research into how beliefs are formed from every day, moment-to-moment interactions with the environment. In this study, 27 people with a diagnosis of schizophrenia and a control group of 33 healthy people played a simulated "Rock Paper Scissors" game against a computerised fictional opponent. The opponent favours one choice over others, with the occasional random decision.  During the games, participants were required to play-to-win in a time-pressured way by spotting the evolving favoured strategy of the opponent.  Participants also had to declare at any point in the game when they felt confident they had found the winning strategy.

Dr Dan Joyce, from the IoP at King’s and lead author of the study, says: “Imagine a game of rock paper scissors where you are playing against someone who constantly plays ‘rock’, after a couple of goes, you probably decide to play ‘paper’ over and over. You win. Then your opponent plays ‘scissors’. We found that healthy controls generally discounted this as a random event, and continued playing their initial move, which from experience, helped them win. Participants with schizophrenia however, attributed much more importance to these random events, and were unable to integrate their experience in a meaningful way.”

The study found differences in the way people with schizophrenia use existing evidence to support a belief in their opponent's strategy. People with schizophrenia were over confident in their beliefs and attributed importance to random events others would deem meaningless, resulting in an unreliable belief about the best way to win. Despite this, people with schizophrenia were much more likely to declare early in the games that they had found the winning strategy.

The research, which uses computational models to analyse people’s behaviour may explain how delusional beliefs are formed, and how, even with these impaired beliefs in place, the so-called 'metacognitive' confidence in these beliefs is higher than is justified by objective evidence in the world.

Dr Sukhi Shergill, Head of the Cognition, Schizophrenia and Imaging Lab at the IoP at King’s, says: “The exciting thing about this work is that there is very little research that examines real live interaction between people with psychotic illness and other folk - and even less that uses behavioural computational analyses to establish mathematical predictions about how the behaviour differs from that of healthy people - this is a very rare paper that does both of these. It show that patients with schizophrenia are not able to use their experience to guide their decision making, as in healthy people, but despite this, they still are over confident in the decisions they make. We show how that leads to an increased likelihood of maintaining erroneous beliefs, such as paranoid delusions.”

Find out more about the CSI Lab's research on metacognition in schizophrenia

Paper reference: Joyce, D. et al. ‘Examining Belief and Confidence in Schizophrenia’ Psychological Medicine doi: 10.1017/S0033291713000263

Image credit: Wikimedia Commons GNU Free Documentation License

For further information, please contact Seil Collins, Press Officer, Institute of Psychiatry, King’s College London. Email: or tel: (+44) 0207 848 5377