Comparative judgements and higher cognitive processes in human numerosity estimation

Perceiving the number of objects in a scene is fundamental to human behaviour and mathematics. Standard numerosity experiments assume that brief stimuli block higher cognitive processes, implying that the signature characteristics of human numerosity estimation—such as exact enumeration of small numbers, underestimation of large numbers, and scalar variability (Weber’s law)—arise from specialised sensory representations. Here we challenge this century-old assumption and find that it does not hold. Combining qualitative, correlational, and experimental methods, we provide evidence that several estimation signatures, previously attributed to specialised sensory representations, likely arise from general cognitive processes. We conducted standard numerosity estimation experiments with brief (100 ms) dot patterns and visual masking. In interviews, participants reported using common cognitive processes, including comparing to previous examples and counting from visual memory. Quantitative surveys confirmed that the reported processes correlated with their expected estimation signatures. Preregistered experiments further validated several predictions for how the processes affect their corresponding signatures. These results call for a re-evaluation of current models of numerical cognition and the development of new experimental methods to better understand how numerosity is represented and processed in sensory circuits.