Final answer:
Behaviorism is the psychological theory that behavior is influenced by observable stimuli and responses, with key figures such as John B. Watson and B. F. Skinner instrumental in its development.
Step-by-step explanation:
The psychological theory that suggests behavior is influenced by observable stimuli and responses is known as behaviorism. This theory was developed in the early 20th century and focuses on studying and understanding behavior through observable stimuli without emphasizing the role of mental states. Behaviorism posits that all human behavior can be understood in terms of the interactions between external stimuli and the responses they elicit. Two key figures associated with behaviorism are John B. Watson, who is often considered the father of behaviorism, and B. F. Skinner, who is famous for his work on operant conditioning. Behaviorism's emphasis on the environmental factors shaping behavior is seen as a reaction against the introspective methods common in psychology at the time.