Grooming reciprocation in Himalayan tahr and the cognitive constraint hypothesis

Abstract

The cognitive constraint hypothesis maintains reciprocity is rare among animals because it requires cognitive capabilities that are rare, if not absent, in animals. In particular, it suggests that temporal discounting, limited memory, and limited capability of complex calculations make long‐term reciprocation essentially impossible for animals. The cognitive constraint hypothesis therefore predicts that, if reciprocity ever occurs in animals, it should always be immediate. In this study, we tested for long‐term reciprocation in Himalayan tahr (Hemitragus jemlahicus), a species that is not notable for its advanced cognitive capabilities. We showed that tahr are able to reciprocate grooming over extended time periods, that is, that they groom preferentially those individuals from which they receive more grooming even when all cases of immediate reciprocation are excluded from analysis. These results do not support the cognitive constraint hypothesis. We note the cognitive constraint hypothesis makes two silent assumptions: that all reciprocation is necessarily calculated and that it is based on partner control processes. We suggest these assumptions are unwarranted, and that most group living animals base their ability to reciprocate on emotionally based partner choice.

Interdisciplinary perspectives on the principle of reciprocation

“…Yet, this special issue provides convincing evidence for reciprocity in species with different cognitive skill sets. First, Schino and colleagues show that Himalayan thar (Hemitragus jemlahicus) reciprocate grooming not only immediately but also over prolonged time scales (Schino et al, 2024). The authors argue that rather than an explicit understanding of cost-benefit calculations, there are less cognitively demanding mechanisms such as emotions underlying thar's reciprocal actions (reviewed in Schino & Aureli, 2010;Schweinfurth & Call, 2019a).…”