From the very beginning of the study of reinforcement, there has been conflict between two fundamentally different interpretations. The first, exemplified by Thorndike, is that reinforcement is essentially a very simple process. When Thorndike placed his cats in the puzzle box for the first time, they struggled frantically to escape and reach the food dish outside. Eventually, after 8–10 minutes of scrambling about, a cat might accidentally contact the release mechanism and escape. If the cat formed a rational appreciation of the situation, he argued, it should repeat this response immediately on subsequent trials:

In all the scores of animals Thorndike tested, not once did he observe sudden and enduring improvement of this kind. In most instances, improvement over trials was a slow, gradual affair. (See Figure 4.2 for some representative records.)

To Thorndike, this gradual improvement in performance, with its occasional reversals and failures, did not at all resemble the behavior of a rational animal fully aware of the relationship between the latch and the door:

Reinforcement, he concluded, caused the formation of an association between the rewarded response and the stimuli that were present at the time, so that thereafter these stimuli would elicit the response automatically.