Effects of motor response pattern on serial dependence in visual confidence

Visual confidence -- the evaluation of one’s own performance in a visual task -- demonstrates serial dependence when the visual task is performed over a series of trials. Despite the converging evidence for such serial effects on visual confidence, the underlying mechanisms remain unclear. The present study investigated the effects of motor response pattern on serial dependence in visual confidence using a novel paradigm. In each trial, participants performed a left-right, direction-discrimination task on a random-dot motion pattern. Simultaneously, they rated their confidence by pressing one of the 8 keys (2 directions x 4 points). Task difficulty was manipulated by varying motion coherence, which had been calibrated to individual participant’s direction discriminability using adaptive staircase. In the main experiment, we sequenced trials based on their difficulty levels, such that a (target) medium-difficulty trial was preceded by either easy or difficult trials. In Experiment 1, we found that confidence rating in target trials was higher when they were preceded by easy trials than by hard trials, despite matched task performance of the target trials between the two conditions. This suggests that confidence judgments can be biased in a series of tasks. In Experiment 2, we employed the same paradigm but instructed participants to respond either using the keyboard as in Experiment 1 or using the mouse to indicate confidence on one of two (left and right) on-screen, continuous sliders. We found the same serial confidence bias only when mouse was used in both preceding and target trials. Interestingly, using the meta-d’ analysis, we found that metacognitive sensitivity was higher when participants switched from mouse (preceding) to keyboard (target). In other words, repeatedly responding in the same motor pattern could impair metacognitive sensitivity. This suggests that the continuity in motor response pattern may contribute in producing serial effects on visual confidence.