What determines if you are confident in your decisions? In the perceptual domain, the standard answer to this question is usually “signal strength.” The idea is that we are more confident for larger, brighter, less noisy stimuli. Beyond that, however, our previous decisions also have an impact: after making a decision with high confidence, we are more likely to be very confident again. This is an example of the ubiquitous sequential effect that turns up everywhere in perception.
But what if your previous decision was for a different task altogether? Does your confidence on a completely different task still influence you when you are deciding on your current task?
Our design was simple: present 40 letters (Xs and Os) in different colors (red or blue), and then ask participants to judge whether there are more Xs or Os, and whether there are more blue or red letters. Even though the processing of letter form and color tend to be separated in the visual system, we find that, on a trial-by-trial basis, confidence on one task predicts the confidence on the other.
A number of analyses and control experiments confirmed that the effect is not due to trivial reasons such as motor priming, attentional fluctuations, or confidence drifts. What really convinced us, though, was our causal manipulation. We increased the difficulty of one of the tasks, so that confidence decreased. Lo and behold, we found a corresponding decrease in the confidence in the other task. In other words, the lowered confidence in the first task leaked into the second task.
Why does confidence leak happen? We think that people believe that the environment is consistent (autocorrelated) and thus an easy trial ought to be followed by another easy trial, even if the tasks are different. We constructed a Bayesian model that demonstrates how this assumption would naturally produce the observed confidence leak.
Who are the people that show more of this (suboptimal) confidence leak? In a separate experiment, we found that people with lower gray matter volume in the anterior prefrontal cortex (aPFC) exhibited higher confidence leak and so did people with lower metacognitive sensitivity.
It is interesting to consider the limits of the phenomenon. Would confidence leak appear for tasks that involve different modalities (e.g., vision and audition)? Would it happen for memory or general knowledge tasks? If our model is correct, as long as people are willing to assume that the difficulty of different tasks is correlated in the natural environment, confidence leak would invariably follow.