Abstract
When we don’t know what we’ve seen, we often guess. How? One possibility is that guessing is "random", such that observers sample from a uniform distribution across feature values. For example, if shown a colored patch or oriented line, observers who don't know what they saw might randomly select a color or orientation (e.g., lapse parameter). Alternatively, Bayesian accounts contend that guesses are drawn from distributions weighted toward prevalent, high-precision values; on this account, a guessing observer might choose saturated colors, cardinal orientations, or other features with high prior probability and perceptual precision. However, a third possibility is that guessing is anti-Bayesian—e.g., by leveraging strategic metacognition, uncertain observers may select feature values that they *struggle* to perceive, as if reasoning “it must have been tilted, because if it were vertical, I would have noticed it.” These accounts make strikingly different predictions about guessing: (1) random values; (2) biases towards high-precision values; (3) biases toward low-precision values. Here, we show that guesses can derive from the metacognitive strategy, relying on an intuitive estimation of one’s own perceptual capacities. Adult observers performed a visual working memory task in which three oriented arrows simultaneously appeared at isoeccentric locations for 0, 16, 33, 66, or 132ms, before being masked. Afterwards, observers reported the orientation of a single target arrow, indicated by a response cue. On trials where stimuli were presented, observers were significantly above chance at reporting arrow orientation across display times. However, on 0-ms “guess” trials, when stimuli were physically absent, participants' guesses revealed systematic non-constancies. Specifically, observers were less likely to report cardinal orientations (which are represented with higher precision, and are more common in natural environments) than oblique orientations. Both psychophysical and computational modeling results suggest that guessing is both strategic and metacognitive: Guessing reflects the complement of precision.