PT  - JOURNAL ARTICLE
AU  - James A. R. Marshall
AU  - Andreagiovanni Reina
AU  - Célia Hay
AU  - Audrey Dussutour
AU  - Angelo Pirrone
TI  - Magnitude-sensitive reaction times reveal non-linear time costs in multi-alternative decision-making
AID  - 10.1101/2021.05.05.442775
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.05.05.442775
4099  - http://biorxiv.org/content/early/2021/09/15/2021.05.05.442775.short
4100  - http://biorxiv.org/content/early/2021/09/15/2021.05.05.442775.full
AB  - Optimality analysis of value-based decisions in binary and multi-alternative choice settings predicts that reaction times should be sensitive only to differences in stimulus magnitudes, but not to overall absolute stimulus magnitude. Yet experimental work in the binary case has shown magnitude sensitive reaction times, and theory shows that this can be explained by switching from linear to geometric time costs, but also by nonlinear subjective utility. Thus disentangling explanations for observed magnitude sensitive reaction times is difficult. Here for the first time we extend the theoretical analysis of geometric time-discounting to ternary choices, and present novel experimental evidence for magnitude-sensitivity in such decisions, in both humans and slime moulds. We consider the optimal policies for all possible combinations of linear and geometric time costs, and linear and nonlinear utility; interestingly, geometric discounting emerges as the predominant explanation for magnitude sensitivity.Competing Interest StatementThe authors have declared no competing interest.