Which term describes complex behavior that is not modified by experience?

The term that describes complex behavior that is not modified by experience is instinct. Instincts are innate patterns of behavior that organisms are born with, and these behaviors are typically triggered by specific stimuli in the environment. Instinctual behaviors are often essential for survival and reproduction, such as nest building in birds or migration patterns in certain species.

In contrast, learning and conditioning refer to changes in behavior that occur as a result of experience. Learning indicates a more flexible and adaptive form of behavior in which individuals can alter their responses based on past interactions with their environment. Behaviorism is a psychological perspective that emphasizes observable behaviors and the processes by which they are learned, but it does not specifically refer to innate behaviors like instinct does. Thus, instinct is the most accurate term for behaviors that are fixed and not influenced by prior experience.