Reciprocal altruism in Norway rats

Abstract

Reciprocal altruism has been proposed to generate evolutionarily stable levels of cooperation, but empirical evidence in non‐human animals is contentious. A series of experimental studies on Norway rats revealed that these animals reciprocate received help by using decision rules characterising direct and generalized reciprocity. The direct reciprocity decision rule states that individuals should help someone who previously helped them, whereas the generalized reciprocity decision rule implies that individuals should help anyone after having received help from someone. Here, we present results from meta‐analyses assessing if Norway rats generally help partners according to the direct and generalized reciprocity decision rules by giving more help sooner and matching help received either to previously cooperative partners or to anyone after having received help from a conspecific. We also compared the rats' performance when applying the direct or generalized reciprocity decision rules. Results from these meta‐analyses clearly show that female and male focal rats help partners according to the direct reciprocity decision rule. Rats did not adjust the amount of help they gave by matching the help they received according to both the direct and generalized reciprocity decision rules; however, they may adjust the duration to the first help they gave by matching the help they received according to the direct reciprocity decision rule. Female, but not male, focal rats help partners according to the generalized reciprocity decision rule. There was no apparent difference in the help given by female rats to partners between the direct and generalized reciprocity decision rules. These results (i) demonstrate, across a wide range of studies, the reciprocal cooperation of Norway rats by use of decision rules denoting direct and generalized reciprocity, and (ii) suggest that rats may frequently apply the cognitively less demanding decision rule of generalized reciprocity, unless they need to distinguish between individuals differing in helpfulness.

Assessment of help value affects reciprocation in Norway rats

“…Norway rats represent a unique model system to study the behavioural mechanisms underlying reciprocal cooperation [ 74 – 76 ]. Previous studies showed that wild-type Norway rats return more help to partners that had provided more benefit to them before [ 25 ], and to partners that were food-deprived or in poor body condition [ 2 , 18 ], which can lead to enhanced begging for help [ 19 , 40 , 52 ].…”

Interdisciplinary perspectives on the principle of reciprocation

“…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). Second, a meta-analysis on foodprovisioning in Norway rats (Rattus norvegicus) showed that rats share food readily and reciprocally with others (Engelhardt & Taborsky, 2024). The rats help conspecifics who helped them in the past, following a 'You helped me, so I help you' rule.…”

Evidence suggesting that reindeer mothers allonurse according to the direct reciprocity and generalized reciprocity decision rules

“…Direct reciprocity was reported across several taxa, including mammals [28,29,[56][57][58][59][60][61][62] (e.g. vampire bats, Desmodus rotundus [57,58] and Norway rats, Rattus norvegicus [29,[59][60][61][63][64][65]), birds [20,21], fishes [54,55], and microorganisms [66,67]. Generalized reciprocity was reported in humans [68,69], female Norway rats [60,64,70], dogs, Canis familiaris [71], capuchin monkeys, Sapajus apella [72], however generalized reciprocity was not supported in male Norway rats [64,73], long-tailed macaques, Macaca fascicularis [74] and in vampire bats [57].…”

“…vampire bats, Desmodus rotundus [57,58] and Norway rats, Rattus norvegicus [29,[59][60][61][63][64][65]), birds [20,21], fishes [54,55], and microorganisms [66,67]. Generalized reciprocity was reported in humans [68,69], female Norway rats [60,64,70], dogs, Canis familiaris [71], capuchin monkeys, Sapajus apella [72], however generalized reciprocity was not supported in male Norway rats [64,73], long-tailed macaques, Macaca fascicularis [74] and in vampire bats [57]. Generalized reciprocity is also known as upstream tit-for-tat [47], upstream indirect reciprocity [75], upstream reciprocity [76], pay it forward [77][78][79], and serial reciprocity [80].…”

“…Cooperation was better explained by direct reciprocity than relatedness [29,57,102] and generalized reciprocity [74] in some empirical studies. Direct reciprocity and generalized reciprocity can co-exist, such as in humans [68], female Norway rats [60,64,70], and in dogs [71,103]. Theoretically, cooperation usually stems from the interaction of multiple evolutionary mechanisms [99][100][101]104,105].…”