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 best explained by assuming a logarithmic distance model between numerosities. In contrast, research about the capacity to compare ratios of numerosities has received less attention. In this paper, we directly contrasted the linear and logarithmic distance models in the context of a visual ratio comparison task. We present data from two experiments where adult participants completed a visual ratio comparison task with stimuli consisting of ratios of numerosities of sets of dots. Results revealed that, at the group level, the logarithmic distance model provided a superior fit to participants' responses and response times compared to the linear model. However, at the individual level, results were less conclusive. Overall, our findings suggest that visual ratio comparison follows psychophysical laws similar to those observed in numerosity comparison, contributing to disentangle the possible underlying cognitive mechanisms processes.