Which word describes a lack of originality or innovation in behavior?

The term that best captures a lack of originality or innovation in behavior is "unoriginal." This word specifically denotes an absence of new or unique ideas, suggesting that someone or something merely replicates existing patterns or concepts rather than producing something fresh or innovative.

In this context, "unoriginal" effectively conveys the idea of a failure to innovate or think outside the box, making it the most appropriate choice for describing a behavior characterized by sameness or a repetitive nature.

While "conventional" also implies adherence to established norms or practices, it does not explicitly convey the notion of lacking originality as directly as "unoriginal" does. "Derisive," on the other hand, relates to mockery or disdain and does not pertain to the concept of originality. Lastly, "creative" stands in stark contrast to the idea of lacking originality, as it implies innovation and the ability to produce original work. Therefore, "unoriginal" is the best fit for the definition provided in the question.