Aversive learning reduces aversive-reinforcer sensitivity in honey bees

Research on associative learning typically focuses on behavioral and neural changes in response to learned stimuli. In Pavlovian conditioning, changes in responsiveness to conditioned stimuli are crucial for demonstrating learning. A less explored, but equally important, question is whether learning can induce changes not only in the processing of conditioned stimuli but also in the processing of unconditioned stimuli. In this study, we addressed this question by combining reinforcer-sensitivity assays with Pavlovian conditioning in honey bees. We focused on aversive shock responsiveness, measuring the sting extension response to electric shocks of increasing voltage, and examined the effect of aversive olfactory conditioning-where bees learn to associate an odor with shock-on shock responsiveness. After experiencing electric shocks during conditioning, the bees showed a persistent decrease in responsiveness to lower voltages, observable three days after conditioning, indicating reduced shock sensitivity. This effect was specific to electric shock, as appetitive conditioning involving a sucrose reinforcer did not alter shock responsiveness, leaving shock sensitivity unchanged. These findings highlight a previously unexplored effect of associative learning on reinforcer sensitivity, demonstrating a lasting decrease of responsiveness to reinforcer intensities perceived as less relevant than that encountered during conditioning.