Kea show no evidence of inequity aversion.

Megan Heaney,Alex H Taylor,Russell D Gray

doi:10.1098/rsos.160461

Megan Heaney, Alex H Taylor + Show 1 more

Open Access

https://doi.org/10.1098/rsos.160461

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Abstract

It has been suggested that inequity aversion is a mechanism that evolved in humans to maximize the pay-offs from engaging in cooperative tasks and to foster long-term cooperative relationships between unrelated individuals. In support of this, evidence of inequity aversion in nonhuman animals has typically been found in species that, like humans, live in complex social groups and demonstrate cooperative behaviours. We examined inequity aversion in the kea (Nestor notabilis), which lives in social groups but does not appear to demonstrate wild cooperative behaviours, using a classic token exchange paradigm. We compared the number of successful exchanges and the number of abandoned trials in each condition and found no evidence of an aversion to inequitable outcomes when there was a difference between reward quality or working effort required between actor and partner. We also found no evidence of inequity aversion when the subject received no reward while their partner received a low-value reward.

Highlights

Inequity aversion is defined as ‘the willingness to sacrifice material pay-offs for the sake of greater equality’ [1]
A non-parametric Friedman’s test was conducted to examine whether there were any differences in the percentage of successful exchanges between the four conditions in which actors always received a reward (EC, Inequity condition (IC), Food control (FC), Free Gift (FG))
This indicates that subjects were not sensitive to inequity in regards to reward quality or the working effort of their partner

Summary

Introduction

Inequity aversion is defined as ‘the willingness to sacrifice material pay-offs for the sake of greater equality’ [1]. Inequity aversion has been often tested in humans and animals using a token exchange paradigm. A subject observes a peer exchange a token for a high- or low-value reward and trades their own token for a reward. Humans demonstrate both disadvantageous inequity aversion, where they react negatively to exchanging a token and receiving less than a peer and advantageous inequity, where they react negatively to exchanging the token and receiving more than a peer, though this second form of inequity aversion appears to be influenced by culture [1].

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