Final answer:
Thorndike's Law of Effect is an early version of Skinner's principle of reinforcement, stating that behaviors with satisfying outcomes are likely to be repeated.
Step-by-step explanation:
An early version of Skinner's principle of reinforcement was Thorndike's Law of Effect. The law of effect, introduced by psychologist Edward Thorndike, states that behaviors followed by satisfying consequences are more likely to be repeated, while those followed by unpleasant consequences are less likely to be repeated. B. F. Skinner built upon Thorndike's law of effect in his work on operant conditioning, focusing on how behaviors are strengthened or weakened by their consequences, utilizing reinforcement and punishment in the systematic studies aided by his invention, the Skinner box.