Which of the following best encapsulates the law of effect?

The law of effect, formulated by Edward Thorndike, states that behaviors followed by satisfying outcomes tend to be repeated, while behaviors followed by unsatisfactory outcomes are less likely to be repeated. This principle is fundamental to understanding operant conditioning and learning, as it highlights the relationship between reinforcement and behavior. When a response produces a favorable outcome, the likelihood of that response being repeated in the future increases. This captures the essence of the law of effect most accurately, making it the best choice.

The other options delve into different concepts. One option discusses complex behaviors being shaped by varying rewards, which relates more to reinforcement schedules and does not directly encapsulate the core idea of the law of effect. Another option refers to reflexive responses and conditioning, which align with classical conditioning rather than the law of effect. Finally, the idea that all behaviors are instinctual is contrary to the principles of learning theory, as it ignores the influence of experience and reinforcement on behavior.