Aversive social learning with a dead conspecific is achieved by Pavlovian conditioning in crickets

Social learning, learning from other individuals, has been demonstrated in many animals, including insects, but its detailed neural mechanisms remain virtually unknown. We showed that crickets (Gryllus bimaculatus) exhibit aversive social learning with a dead conspecific. When a learner cricket was trained to observe a dead cricket on a drinking apparatus, the learner avoided the odor of that apparatus thereafter. Here we investigated the hypothesis that this social learning is achieved by first-order Pavlovian conditioning of an odor (conditioned stimulus) and a dead conspecific (unconditioned stimulus, US). Injection of a dopamine receptor antagonist (flupentixol) before training or testing impaired the learning or execution of the response to the learned odor, as we reported in aversive non-social Pavlovian conditioning in crickets. Moreover, crickets that were trained with a dead conspecific and then received revaluation of the dead conspecific by pairing it with water reward exhibited an appetitive conditioned response (CR) to the odor paired with the dead conspecific. This suggests that execution of the CR is governed by the current value of the US as in non-social Pavlovian conditioning. In addition, we previously suggested that appetitive social learning with a living conspecific is based on second-order conditioning (SOC), and here we showed that SOC is achieved when crickets experienced pairing of a dead conspecific with water reward before experiencing social learning training with a dead conspecific. We conclude that social learning with a dead conspecific is based on Pavlovian conditioning and that this learning can be extended to second-order social learning.