As shown in these photos, pigs are biologically predisposed to root out their food, and raccoons are biologically predisposed to wash their food. Thus, when the Brelands operantly conditioned pigs and raccoons to pick up oversized coins and put them in a bank using food reinforcement, the animals sometimes “misbehaved” (reverted back to these instinctual responses that were part of their food gathering behaviors). The pigs pushed the coins with their snouts, and the raccoons rubbed the coins together in their forepaws. Reverting back to an innate, instinctual response from a learned operant response is called instinctual drift.
John Wilkinson; Ecoscene/Corbis.
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