Psychological research can take a variety of directions while building on theoretical concepts that are commonly shared among the population of researchers. We investigate the question of how agreement or consensus on basic scientific concepts can be measured. Our approach to the problem is based on a state-of-the-art cognitive psychometric technique, implemented in the theoretical framework of cultural consensus theory. With this approach, consensus-based answers for questions exploring shared knowledge can be derived while basic factors of the human decision-making process are accounted for. An example of the approach is provided by examining the definition of behavior, based on responses from researchers and students. We conclude that the consensus definition of behavior is "a response by the whole individual to external or internal stimulus, influenced by the internal processes of the individual, and is typically not a developmental change." The general goal of the article is to demonstrate the utility of a cultural consensus theory-based approach as a method for investigating what current, working definitions of scientific concepts are.