Confidence : a mechanism for the dissociation of biases in binary decision-making tasks

The present study investigated findings discussed in a review by Vickers (1985) which suggest that two types of response bias (relative caution and expectation) have dissociable effects on confidence ratings. We manipulated both biases in an attempt to replicate and expand on Vickers' (1985) review. 32 participants completed two 1-hour sessions in which they undertook a perceptual discrimination task. One of the two biases was manipulated in each session. We found that in correct responses, expectation bias induced higher confidence ratings in responses participants were biased towards, compared to relative caution bias, p < .001. The hypothesised differential effects of the two bias manipulations on confidence ratings goes against the often-assumed unitary conception of response bias (Link, 1975). We also found that this interaction effect differed depending on the accuracy of the response, p < .001, where a flip from the findings in correct responses was found in error responses. This unexpected interaction with accuracy warrants more research. The present research advocates for the importance of confidence as a variable for the understanding and modelling of cognitive processes.