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To wait or not to wait – the role of confidence in decision making

  1. 18.9.2014

    Researchers discover the neural basis of confidence and its effect on decision-making in rats.

    Our confidence in what we know guides our behaviour in both trivial and crucial situations. For example, deciding whether to keep waiting for the bus depends on your confidence that the bus will arrive, and your decision to cross a busy road depends on your confidence that no cars are coming. These decisions rely on the consideration: how sure am I that my expectations are correct?

    In a study published today (18/9/2014) in the scientific journal Neuron, researchers at the Champalimaud Neuroscience Programme in collaboration with researchers at Cold Spring Harbour Laboratory, establish that this sense of confidence is encoded in a specialised area in the brain of rats.

    How can you measure confidence? The researchers hypothesised that confidence could be estimated by the time the rats were willing to invest in waiting for their reward. Our intuition led us to speculate that the animals would be willing to wait longer if they were confident that waiting will give them the outcome they expect. – Says Gil Costa, a graduate student at the CNP. The researchers developed an experiment that addressed this hypothesis directly. We trained the rats on a task where they were presented with a variety of odors. Their job was to choose to go to the left or right, and then wait for their reward.

    To wait, or not to wait? A scheme of the odour discrimination task that was used in this study to estimate confidence. Figure adapted from Lak et al., 2014.

    The researchers were able to establish a correlation between waiting time and the likelihood that the decision of the animal was correct. This correlation gave us a direct estimate of the confidence of the rat. – says Gil Costa. The results matched our expectations, showing high confidence for easily identifiable odours and low confidence for difficult odours. We were also able to show mathematically that waiting longer when you are more confident is exactly the right way to optimise the cost-benefit ratio of waiting for an uncertain outcome.

    Furthermore, the researchers were able to identify the area of the brain that encoded information about confidence. They found that when they deactivated an area of the brain of the rat called the Orbitofrontal Cortex (OFC), rats were able to make the correct decision, but their behaviour showed that they lost the ability to know how confident they were in their decision. When the OFC was deactivated the rats would still make the correct decision. But they were waiting differently – instead of waiting a long time for easily identifiable odours, and a short time for difficult odours, they would wait a random amount of time for either. – Says Zachary Mainen, Principal Investigator at the Champalimaud Neuroscience Programme.

    We found that the OFC is important for the confidence report but not required for making a left-right decision. If they were human they would be essentially making the right choice but saying 'I have no idea if I’m correct’. Says Zachary Mainen. In other words, they would not be conscious of knowing the right answer.

    These results appear to be in line with evidence about the function of human OFC, which seems to be involved in reflecting on the future consequences of ones actions. Using the rat as an animal model to study the mechanisms involved in the function of the OFC allows us to begin to uncover the basis of confidence and decision making in humans. – Concludes Zachary Mainen.

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