The elusive nature of forward blocking effect on running-based taste aversion learning in laboratory rats

It is well documented that rats learn to avoid a taste solution consumed immediately before voluntary running in activity wheels, which represents a form of Pavlovian aversive conditioning based on the taste-running association. Although various behavioral phenomena observed in typical Pavlovian preparations, such as fear conditioning, have also been demonstrated in this setup, evidence of the associative blocking effect is limited. The present study aimed to demonstrate this effect, and the first experiment provided some positive evidence. Conditioning rats with serial presentations of two taste solutions followed by an opportunity to run (A → B → running) resulted in reduced aversion to taste A if the rats had prior experience of running after consuming B (B → running), suggesting that the previously established B-running association blocked the A-running association. However, subsequent experiments failed to yield statistically reliable results, raising questions about the robustness of the blocking effect on running-based taste aversion learning.