Final answer:
Wilhelm Wundt's psychological research was centered on the issue of consciousness, using introspection to study conscious experience, which contrasted with the later emergence of behaviorism that focused on observable behavior.
Step-by-step explanation:
When Wilhelm Wundt started his psychological research, a key issue was consciousness. Wundt, often recognized as the father of psychology, established psychology as a scientific study of conscious experience. He used introspection to examine conscious experience, an approach that later diverged into different schools of thought within psychology. One of the most influential schools that emerged in opposition to Wundt's focus on consciousness was behaviorism, which focused on observable behavior and was pioneered by figures such as John B. Watson and B.F. Skinner. This shift marked a departure from investigating cognition and the inner workings of the mind to an emphasis on external, observable behavior. However, the later emergence of the cognitive revolution in the mid-20th century signaled a renewed interest in mental processes, such as thinking, problem-solving, and information processing.