Differential Responding by Rhesus Monkeys (Macaca mulatta) and Humans (Homo sapiens) to Variable Outcomes in the Assurance Game

Abstract

. (2014). Differential responding by rhesus ronkeys (Macaca mulatta) and humans (Homo sapiens) to variable outcomes in the assurance game. Animal Behavior and Cognition, 1(3), 215-229. doi: 10.12966/abc.08.01.2014 Abstract -Behavioral flexibility in how one responds to variable partner play can be examined using economic coordination games in which subjects play against a variety of partners and therefore may need to alter their behavior to produce the highest payoff. But how do we study this behavioral flexibility once players have settled on a response? Here, we investigated how responding by rhesus monkeys (Macaca mulatta) and humans (Homo sapiens) playing a computerized single-player version of a coordination game, the Assurance game, changed as a function of the variable responses (Stag/Hare) generated by multiple simulations (SIMs). We were interested in whether individuals could track and differentially respond to changing frequencies of Stag and Hare play by the SIMs, especially with regard to the payoff dominant (Stag-Stag) outcome, something that could not be done with real partners as they quickly settled on the Stag response. For both monkeys and humans, there was a linear relationship between proportion of Stag play by the subject and the likelihood of the Stag choice by the SIM such that both species increased their use of Stag as the SIM increased its use of the Stag response. However, humans more closely matched their proportion of Stag responses to that of the SIM, whereas monkeys adopted a different, but equally effective, strategy of exploiting the higher-paying Stag alternative. These results suggest that monkeys and humans demonstrate sensitivity to a dynamic game environment in which they encounter variable contingencies for the same response options, although they may employ different strategies to maximize reward.

Human and monkey responses in a symmetric game of conflict with asymmetric equilibria

“…We did not have a prediction for the rhesus monkeys. Our work with the assurance game indicated that they found the payoff dominant Nash equilibrium with a simple propensity to choose the more valuable Stag option (Parrish et al 2014), but this would be unstable and inefficient whether they both played Fight or Yield in our game of conflict. Other work, however, shows that rhesus outperform capuchins on at least some complex cognitive tasks that require them to monitor outcomes (e.g., metacognition tasks: Beran and Smith 2011;Beran et al 2009), leaving open the possibility that they would be able to settle on at least one efficient Nash equilibria using a mechanism that wasn't apparent in the previous work.…”

“…A follow-up study in which subjects played a computer simulated partner demonstrated that humans and rhesus used different mechanisms. Rhesus showed a consistent propensity to play Stag across all patterns of random play (0%, 25%, 50%, 75%, and 100% Stag) whereas humans matched the frequency with which the simulation played Stag (Parrish et al 2014). Thus, the evidence indicates that rhesus were selected to be able to coordinate, but using a different, and presumably simpler, mechanism than is seen in humans.…”

“…We tested four adult male rhesus monkeys in a specially designed paired testing area used in the previous study (Brosnan et al 2012;Parrish et al 2014). All features of the procedure were the same as those described for the capuchins, except that due to testing constraints the rhesus monkeys were given only 5 sessions each of Stage 1 and Stage 2.…”

Capuchin monkeys (Sapajus[Cebus]apella) play Nash equilibria in dynamic games, but their decisions are likely not influenced by oxytocin

“…Rhesus monkeys, chimpanzees, and humans, however, were still able to reach the payoff‐dominant NE when presented with the simultaneous AG. For humans and chimpanzees there is evidence that they understood a specific strategy (Brosnan et al, ), although for rhesus monkeys our evidence indicates that they simply developed a preference for the strategy, Stag , that most often provided the highest payoff (Parrish et al, ).…”

Human and macaque pairs employ different coordination strategies in a transparent decision game

“…The performance of rhesus monkeys (Macaca mulatta) was more similar to humans than capuchins, especially when no information about the current choice of the partner was available 31 . Interestingly, in a computerized Stag Hunt game, humans adapted more closely than macaques to a simulated partner's stag choice probability, showing that different species might employ distinct but overall fairly successful strategies to maximize reward in a dyadic context 32 .…”