The underestimation bias of the number sense in positive-valence stimuli

Number sense, the ability to rapidly recognize quantities, estimate magnitudes, and infer relationships between numbers, is a fundamental perceptual attribute and is relatively independent of top-down cognitive processing. However, when positive-valence stimuli are presented, whether its independence remains needs exploring. Since positive-valence enhances the frequency and intensity of the actions it reinforces, this study investigates the influence of positive-valence stimuli on number sense through three behavioral experiments, examining biases induced by both positive emotion and monetary reward. All experiments adopted a numerical comparison task, with positive-associated and neutral stimuli randomly presented as units of dot arrays. Results revealed that both positive emotion and monetary reward elicited an underestimation effect in number sense, while this underestimation tendency did not occur in neutral stimuli. This research provides evidence for the perceptual underestimation bias in number sense associated with positive-valence stimuli, which could be explained by the predictive processing theory.