Abstract
In a dark environment, participants cannot visually confirm the task outcome, possibly leading them to report their performance as advantageous to themselves. Although previous studies have suggested this point, none of the experimental verification has been conducted. In the present study, we directly manipulated the ambiguity of the task outcome and test its effect on participants' reported scores. One hundred and two participants performed the task of extracting a target ball from a box with a one-in-six chance of success. We manipulated the similarity between the appearance of targets and non-targets to make different ambiguities. After 30 trials, participants reported the times of success as their score. As a result, there was no significant difference in the reported score between the two conditions (p = .054). However, because the effect size was relatively large (Cohen's d = .321), we will conduct further studies by revising the task and sample size.
