Vicarious reward unblocks associative learning about novel cues in male rats

Many species, including humans, are sensitive to social signals and their
valuation is important in social learning. When social cues indicate that
a conspecific is experiencing reward, they could convey vicarious reward
value and prompt social learning. Here, we introduce a task that
investigates if mutual reward delivery in male rats can drive social
reinforcement learning in a formal associative learning experiment. Using
the blocking/unblocking paradigm, we found that when actor rats have fully
learned a stimulus-self reward association, adding a cue that predicted
additional reward to a partner unblocked associative learning about this
cue. In contrast, additional cues that did not predict partner reward
remained blocked from acquiring positive associative value. Importantly,
this social unblocking effect was still present when controlling for
secondary reinforcement but absent when social information exchange was
impeded, when mutual reward outcomes were disadvantageously unequal to the
actor or when the added cue predicted reward delivery to an empty chamber.
Taken together, these results suggest that mutual rewards can drive
associative learning in rats and is dependent on vicariously experienced
social and food related cues.