Noa Perlmutter¹, Chaz Firestone¹, Ian Phillips¹; ¹Johns Hopkins University

We are aware of the world and its properties; for example, we can see the number, size, and motion of objects around us. Are we also aware of the internal processes that generate these percepts? Whereas it is controversial whether higher-level cognitive processes are accessible to introspection (e.g., knowing why we make various choices), basic perceptual biases are widely assumed to be closed off from introspection. In contrast to this consensus, here we reveal successful introspection of three classic effects in vision and visual memory: numeric underestimation, size contrast, and representational momentum. Experiment 1 investigated numeric underestimation: Subjects briefly saw an array of 11-100 dots, and estimated their numerosity; on a subset of trials, subjects were then asked whether they thought they had underestimated or overestimated. Experiment 2 investigated the Ebbinghaus illusion: Subjects saw a target circle surrounded by flankers of variable size, and adjusted a second circle to match the target; subjects were then asked whether they thought they had underestimated or overestimated. Experiment 3 investigated representational momentum: Subjects saw a fish glide across the screen and disappear, and estimated its final seen location; subjects were then asked whether they thought their estimate was too far left or right. We replicated all three biases: Subjects underestimated numerosity, were influenced by flankers, and extrapolated motion. Strikingly, however, all three experiments also revealed awareness of the effects themselves. For example, in Experiment 1, subjects correctly answered that they underestimated numerosity. And in Experiments 2 and 3, they showed trial-by-trial awareness of their biases, as computed by detection-theoretic statistics. These findings go beyond successful metacognition of performance (i.e., knowing whether one is performing well or poorly) to awareness of directional effects themselves, suggesting deeper and subtler access to internal mental processes than traditionally assumed.