Dynamics of visibility, confidence, and choice during eye movements

We study the dynamics of objective and subjective measures of visibility and choice in brief presentations occurring within a fixation during free eye-movements. We show that brief presentations yield homogeneous levels of performance in a window that extends almost throughout the entire fixation. Instead, confidence judgments vary for presentations occurring at different moments of the fixations. When the target occurs close to the onset of the fixation, it is reported accurately but with lower values of confidence; when it occurs close to the end of the fixation, it is reported with high confidence (Experiments 1 and 2). Consistently, in experiments in which participants can freely choose to report items, we observe a report bias toward the end of the fixation, where the maximum of confidence occurs for experiments with a single target (Experiments 3 and 4). Hence, these results suggest that confidence is not merely a measure of accumulated stimulus energy but instead varies reflecting an endogenous integration process by which later stimuli are assigned greater confidence.