 Reactivity, Hawthorne effect is a type of reactivity. So reactivity happens when an organism knows they're being observed or when an observer is present and organisms behavior is often changed. Imagine if you're at home and your parents are watching you. The behavior that you engage in will probably be different than if your parents are not watching you. Well, guess what? That's reactivity and the same thing happens in experimental settings or in research settings or applied settings. When you're watching something, the behavior changes. So a thing observed changes. So if you can figure out what that quote is from, more power to you. But it's a well-known phenomenon. It occurs across many different areas of science. We have huge problems with reactivity phenomenon when you are trying to help someone change their behavior or when they're engaging in a problem behavior and trying to get it to reduce. Oftentimes the presence of the observer automatically reduces the behavior. So what we try to do is teach others to do the observations or teach self-recording, things like that. Or you just keep the observer present for a long damn time until they get used or they habituate to the presence of the observer and they don't engage and they don't worry about the person being present anymore. There you go.