Flawed stimulus design in additive-area heuristic studies

Studying magnitude perception using visual item arrays is notoriously difficult due to the intricate relationship between various dimensions including number, area, density, etc. When item arrays are constructed with a skewed and unbalanced distribution of their dimensional properties, false conclusions are easily made. This kind of flawed stimulus design was identified in a series of recently published studies that argue for an additive-area heuristic whereby people are more sensitive to the sum of the vertical and horizontal element axes in each item than the sum of the mathematical area of each item. By analyzing the dimensional properties of the stimuli used in the original studies (e.g., Yousif & Keil, 2019) using the mathematical framework for constructing stimulus parameters (DeWind et al., 2015) and by re-analyzing the data from another previous work on area judgment (Tomlinson et al., 2020), this paper demonstrates how skewed and unbalanced stimulus sampling leads to false conclusions.