Quantity Estimation by Repeated Comparative Judgments.

Many species can discriminate nonsymbolic quantities, but only humans transform such perceptual magnitudes into symbolic numbers and mathematics. The process by which this transformation occurs remains debated. Here, we propose a computational model of human quantity estimation which synthesizes four general concepts established over the history of cognitive science: (1) nonsymbolic quantity representations; (2) a general capacity for comparative judgment; (3) associative memory; and (4) an anchoring-and-adjustment mechanism. We tested model predictions in preregistered experiments where participants estimated briefly displayed dot arrays. The model reproduced key psychophysical signatures of human quantity estimation across stimulus durations (100, 500, and 1000 ms) and replicated human calibration effects induced by exposure to veridical reference quantities. The results suggest that the psychophysics of symbolic estimation observed in humans can be explained by an extension of the evolutionarily ancient capacity for quantity discrimination.