Brain waves track risk separately from reward value
Brain waves that track feedback are strongly influenced by the level of risk a person takes, even when the average expected payoff remains exactly the same.
Source
Neural correlates of feedback processing in decision-making under risk
What they did
Researchers designed a two-choice gambling task where participants chose between a low-risk option and a high-risk option. In a pilot study with 50 participants, they analyzed how choices changed based on previous outcomes and overall bank balance. In the main experiment, 20 participants performed hundreds of trials of this task while researchers recorded their brain activity using electroencephalography.
What they found
Behaviorally, participants were generally risk-averse, preferring low-risk options, but became more risk-seeking after experiencing losses. Electrophysiological recordings revealed that the feedback-related negativity—a brain wave linked to outcome processing—distinguished between gains and losses only when participants made high-risk choices. Additionally, a late positive brain wave was larger for losses compared to gains and was overall enhanced during high-risk choices, reflecting the increased motivational significance of risky outcomes.
The limits
What it doesn't show
First, because the probability of winning was kept high to mimic typical decision environments, the study confounded feedback valence with frequency, meaning positive feedback occurred more often than negative feedback. Second, the small sample size of 20 participants in the brain-imaging portion limits the generalizability of the brain-behavior correlations. Lastly, the study could not separate the impact of the actual size of the outcome from the brain's calculation of reward prediction errors, meaning further research is needed to isolate these factors.
Key terms
- feedback-related negativity
- A negative-going brain wave that peaks shortly after a person receives feedback about their choice, often associated with processing losses or errors.
- P300
- A positive-going brain wave that peaks after feedback, believed to reflect the motivational significance or salience of an event.
- P200
- An early positive-going brain wave associated with early attentional processing of emotional or highly relevant stimuli.
- reward prediction error
- The difference between the reward an individual actually receives and the reward they expected to receive, which drives reinforcement learning.
- risk-averse
- A decision-making preference where an individual chooses options with lower variability and smaller potential losses over riskier options with identical expected values.
- expected value
- The mathematical average payoff of a decision, calculated by multiplying each possible outcome by its probability of occurring and summing those values.
Flashcards
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Quiz yourself
Which of the following frontolimbic brain structures is primarily implicated in evaluating unfavorable outcomes, assessing risks, and predicting decreased risk-taking behavior?
Common questions
Why did the researchers make the expected values of the high-risk and low-risk options equal?
By keeping the expected values equal, the researchers ensured that any preference for one option over the other was driven purely by the participant's attitude toward risk, rather than a rational preference for a higher average payout.
What is the difference between the feedback-related negativity and the P300 in this study?
The feedback-related negativity is highly sensitive to the immediate difference between positive and negative feedback specifically during high-risk decisions. In contrast, the P300 is sensitive to both the positive-versus-negative nature of feedback and the overall risk level of the decision, reflecting how motivationally significant the outcome is.
How does a participant's current bank balance affect their risk-taking behavior?
Participants tended to be cautious and protect their earnings when their total account balance was positive, but they became more willing to take big risks when their balance fell below zero, likely in an attempt to recoup their losses.
What does the early P200 brain wave tell us about how we process risk?
The P200 was larger for losses and high-risk decisions shortly after feedback. This suggests that the brain starts evaluating the stakes and emotional impact of a risky decision almost immediately, long before conscious processing is complete.
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