Irrational risk aversion in an ant

De Agro, Massimo and Grimwade, Daniel and Bach, Richard and Czaczkes, Tomer J. (2021) Irrational risk aversion in an ant. ANIMAL COGNITION, 24 (6). pp. 1237-1245. ISSN 1435-9448, 1435-9456

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Abstract

Animals must often decide between exploiting safe options or risky options with a chance for large gains. Both proximate theories based on perceptual mechanisms, and evolutionary ones based on fitness benefits, have been proposed to explain decisions under risk. Eusocial insects represent a special case of risk sensitivity, as they must often make collective decisions based on resource evaluations from many individuals. Previously, colonies of the ant Lasius niger were found to be risk-neutral, but the risk preference of individual foragers was unknown. Here, we tested individual L. niger in a risk sensitivity paradigm. Ants were trained to associate one scent with 0.55 M sucrose solution and another with an equal chance of either 0.1 or 1.0 M sucrose. Preference was tested in a Y-maze. Ants were extremely risk-averse, with 91% choosing the safe option. Based on the psychophysical Weber-Fechner law, we predicted that ants evaluate resources depending on their logarithmic difference. To test this hypothesis, we designed 4 more experiments by varying the relative differences between the alternatives, making the risky option less, equally or more valuable than the safe one. Our results support the logarithmic origin of risk aversion in ants, and demonstrate that the behaviour of individual foragers can be a very poor predictor of colony-level behaviour.

Item Type: Article
Uncontrolled Keywords: COLLECTIVE DECISION-MAKING; LASIUS-NIGER; SENSITIVITY; HONEYBEES; BEHAVIOR; VARIABILITY; SELECTION; VARIANCE; CHOICES; Risk aversion; Psychophysics; Utility; Value perception; Ants
Subjects: 500 Science > 590 Zoological sciences
Divisions: Biology, Preclinical Medicine > Institut für Zoologie > Zoologie/Evolutionsbiologie (Prof. Dr. Jürgen Heinze)
Depositing User: Dr. Gernot Deinzer
Date Deposited: 01 Sep 2022 04:20
Last Modified: 01 Sep 2022 04:20
URI: https://pred.uni-regensburg.de/id/eprint/47092

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