Final answer:
Examples of reactive effects are behaviors or outcomes that change due to the awareness of being observed or tested and include the Hawthorne effect, John Henry effect, Placebo effect, and Observer effect.
Step-by-step explanation:
Examples of reactive effects include the Hawthorne effect, where individuals alter their behavior because they are aware of being observed; the John Henry effect, where control group participants work harder in reaction to knowing they are in the control group; the Placebo effect, where a person's health outcomes are influenced by their belief in the treatment's effectiveness despite receiving an inert substance; and the Observer effect, which is an overarching term describing changes in behavior or conditions due to the presence of an observer or measurement apparatus.
The Hawthorne effect was first identified in studies conducted at the Western Electric Hawthorne Works, where it was observed that productivity improved when changes were made, such as alterations in lighting levels, because the workers knew they were being observed. This effect must be accounted for in experimental research as it can skew the results. The placebo effect, a type of reactive effect, is also critical to consider, especially in medical studies, because participant beliefs about receiving treatment can cause actual physiological responses, even if the treatment is ineffective (like a sugar pill in controlled trials).