Reference-point dependent reinforcement learning in humans and rats

Rewards and punishments in reinforcement learning are encoded in both absolute and relative manners. Reference-point dependence, a valuation bias shared by adaptation-level and prospect theories, is often proposed as the computational mechanism underlying relative value encoding. However, the extent to which these behavioural and computational mechanisms are conserved across species remains to be fully understood. We therefore designed parallel reinforcement learning tasks in humans and rats to examine reference-point dependence across species. Behavioural analyses showed robust relative value encoding in both species, and computational modelling confirmed that reference-point dependence reliably accounts for behaviour in humans and rats. Despite these major similarities between species, some differences in behavioural and modelling parameters were observed. Overall, our study demonstrates that relative value encoding is a robust feature of reinforcement learning that is conserved across humans and rats.