Final answer:
The rat's behavior of pressing the lever to avoid electric shocks is an example of negative reinforcement, a concept of operant conditioning elucidated by B.F. Skinner to explain behavior modification through consequences.
Step-by-step explanation:
When a rat learns to press a lever to avoid receiving small electric shocks in an environment, it is an example of negative reinforcement. This term refers to the process where a behavior (in this case, pressing a lever) is strengthened because it stops or removes an unpleasant experience (electric shocks). B.F. Skinner, a pioneer in operant conditioning, demonstrated that behaviors could be altered over time using reinforcement. Negative reinforcement involves the removal of a negative condition to increase the likelihood of a behavior being repeated. In contrast, punishment, whether positive or negative, always intends to decrease the likelihood of a behavior.