Who was one of the first scientists to question the role of instinct?

The correct choice is Ivan Pavlov. He is renowned for his pioneering research in classical conditioning, which demonstrated that behavior could be learned rather than being entirely driven by instinct. Pavlov's famous experiments with dogs showed that they could be conditioned to associate a neutral stimulus, such as a bell, with food, leading to salivation when the bell rang, even in the absence of food. This work highlighted the capacity for learned behaviors and challenged the notion that instincts were the sole driving force behind actions.

While other figures, such as Freud, Skinner, and Watson, contributed significantly to behavioral science and psychology, their research focused on different aspects of behavior. Freud concentrated on subconscious drives, Skinner was influential in operant conditioning and reinforcement, and Watson emphasized observable behavior and environmental influences. In contrast, Pavlov's work directly questioned traditional ideas surrounding instinctual behavior, making his contributions particularly relevant to this question.