Data from: Dopamine disruption increases cleanerfish cooperative investment to novel client partners

Social familiarization is a process of gaining knowledge that results from direct or indirect participation in social events. Cooperative exchanges are thought to be conditional upon familiarity with others. Indeed, individuals seem prefer to engage with those that have previously interacted with them, which are more accurate predictors of reward than novel partners. On the other hand, highly social animals do seek novelty. Truth is that the physiological bases underlying how familiarity and novelty may affect cooperative decision-making are still rather obscure. Here we provide first experimental evidence that the level of the dopaminergic influence in cooperative exchanges is constrained on mechanisms of social familiarization and novelty in a cleanerfish, Labroides dimidiatus. Cleaners were tested against familiar and novel Ctenochaetus striatus surgeonfish (a common client species) in laboratorial conditions, and were found to spend more time providing physical contact (also referred to as tactile stimulation) to familiar fish clients. Cleaners learn to use tactile stimulation as a way to reduce the risk of a non-reward outcome, a behavioural response that is even more pronounced when blocking dopamine (DA) D1 receptors. We discovered that the influence of DA disruption on cleaners’ provision of physical contact was dependent on the level of familiarity with its partner, being highly exacerbated whenever the client is novel, and unnoticed when dealing with a familiar one. Our findings demonstrate that DA mediation influences the valuation of partner stimuli and the enhancing investment in novel partners, mechanisms that are similar to other vertebrates, including humans.

社会熟悉度习得是指通过直接或间接参与社会事件以获取相关知识的过程。学界普遍认为，合作交换的发生以对他人的熟悉度为前提条件。事实上，个体似乎更倾向于与此前有过互动的对象进行交往，相较于陌生伙伴，这类对象能更精准地预判奖励回报。但另一方面，高度社会化的动物同样会寻求新奇刺激。然而，熟悉度与新奇性如何影响合作决策的生理学基础，目前仍不甚明晰。本研究首次提供实验证据表明，在裂唇鱼（*Labroides dimidiatus*）的合作交换行为中，多巴胺能（dopaminergic）调控的强度受社会熟悉度与新奇性相关机制的约束。研究人员在实验室环境下，令裂唇鱼分别与熟悉的和陌生的栉齿刺尾鱼（*Ctenochaetus striatus*，一种常见的客户鱼物种）开展互动实验，结果发现裂唇鱼会花费更多时间向熟悉的客户鱼提供身体接触（亦称触觉刺激）。裂唇鱼会习得通过触觉刺激来降低无奖励结果出现的风险，当阻断多巴胺（dopamine，DA）D1受体时，这类行为响应会更为显著。本研究还发现，多巴胺能阻断对裂唇鱼提供身体接触行为的影响，取决于其与互动伙伴的熟悉程度：当客户鱼为陌生个体时，该影响会显著加剧；而当面对熟悉个体时，该影响则无迹可寻。本研究结果表明，多巴胺能介导作用会影响个体对伙伴刺激的价值评估，以及提升对陌生伙伴的行为投入，这类机制在包括人类在内的其他脊椎动物中普遍存在。