Can cleanerfish overcome temptation? A selective role for dopamine influence on cooperative-based decision making

Evidence suggests that animals are selected to make accurate choices and prioritize goals within the constraints of a given social environment to maximize fitness. These decisions are mostly based on complex processes in which value is linked to reward and cues may carry variable incentive salience. However, the level in which the incentive elicited by a cue is able to shift individual choices should differ between individuals and neurophysiological states. Here we used a notorious cooperative cleanerfish species Labroides dimidiatus to probe for differences in the incentive motivational valences given to food cues and then tested for the role of the dopaminergic system in the appraisal of such cues. We found that cleaners differed in Pavlovian conditioned approach behavioural responses to reward-associated stimuli: while the majority were fast to engage physically with the cue plate that indicated future reward delivery (sign trackers), only a few took significantly more time to respond (goal trackers). But amongst those that were considering the sole cue attractive, we discovered that the dopaminergic blockage decreased their initial propensity to approach and touch the cue plate. Our results show that dopamine disruption contributes to shifting the attribution of motivational incentive from the predictive cue towards the actual reward and provides key insight into the physiological framework of cooperative-based decision making.