Which theorist described the importance of the environment in shaping behavior and learning?

The theorist who emphasized the importance of the environment in shaping behavior and learning is John Watson. He is one of the founding figures of behaviorism, a psychological perspective that focuses on observable behaviors and the ways in which they are learned through interactions with the environment. Watson argued that human behavior is primarily a result of conditioning by stimuli in the environment, thereby advocating that the environment has a crucial role in developing a person's behavior over time.

Watson's famous experiments with classical conditioning, such as the Little Albert experiment, demonstrate how emotional responses can be conditioned through environmental factors. This aligns with the central tenet of behaviorism, which posits that the environment considerably influences and determines behavior, rather than innate qualities or cognitive processes.

In contrast, other theorists like Piaget focused more on cognitive development stages, Skinner on operant conditioning, and Vygotsky on social-cultural influences, but Watson specifically highlighted the pivotal role of the environment in behavior and learning, making him the correct answer in this context.