Psychophysical distance between visually presented pairs of ratios

Research has long investigated adults’ capacity to compare numerosities presented visually as sets of dots. It has been proposed that results are better explained by assuming a logarithmic—rather than linear—distance model between numerosities. In contrast, research about the capacity to compare numerosity ratios has received less attention. In this paper, we directly contrasted linear and logarithmic distance models in the context of a visual ratio comparison task. We present data from a task where adult participants compared two sets of red and blue dots and selected the one with a larger ratio of a given color. At the group level, the logarithmic distance model provided a better fit for participants' responses and response times compared to the linear model. At the individual level, the results favored again the logarithmic model for participants’ responses but not for response times. Overall, our findings suggest that visual ratio comparison follows psychophysical laws similar to those observed in numerosity comparison, contributing to disentangling the possible underlying cognitive mechanisms processes.