Instinctive drift refers to the tendency of animals to revert to their innate behaviors despite repeated reinforcement. Breland and Breland demonstrated this concept in an experiment with a raccoon. The raccoon was trained to pick up two coins and place them in a container in exchange for food. Initially, the raccoon learned to associate the coins with food, making them a conditioned stimulus or a substitute for food. However, over time, the raccoon became less willing to put the coins into the container.

Raccoons have a natural tendency to rub the food they hold, and once the coins became a conditioned stimulus for food, the raccoon began to rub the coins together instead of placing them in the container. This behavior illustrates instinctive drift, where the raccoon's innate behavior overpowers the learned behavior. This phenomenon emphasizes the importance of considering innate biological influences when studying learning, as these influences can limit the behaviors that can be trained through reinforcement.

A similar phenomenon, like instinctive drift, occurs in taste aversion. The key idea is that while reinforcement can influence animal behavior, there are biological predispositions that limit the associations animals can form. Studies on taste-aversion learning showed that rats failed to associate certain events with toxicosis. These events included specific flavors, shocks, or audiovisual stimuli. This suggests that certain biological predispositions can affect the associations animals are able to make, demonstrating that innate tendencies restrict learning. These examples highlight that while conditioning shapes behavior, innate tendencies, and biological constraints play a significant role in determining the extent and nature of learning in animals.