What effect describes the changes in behavior that occur due to the expectations set by the researcher?

The Rosenthal Effect refers specifically to the influence that a researcher's expectations can have on the participants' behavior and performance. When researchers have preconceived notions about the outcomes of their studies, whether subconscious or intentional, these expectations can inadvertently shape the way in which participants behave during the research. Essentially, if researchers expect participants to perform better or behave a certain way, those expectations may enhance the likelihood of the participants actually conforming to those expectations, thus skewing the results of the research.

This phenomenon highlights the importance of maintaining objectivity in research settings. A researcher’s anticipation can create a self-fulfilling prophecy, where the treatment or conditions set up by the researcher may lead to the desired outcome simply because the participants are aware of the researchers' expectations. This effect underscores the need for double-blind study designs to mitigate such biases and safeguard the integrity of research findings.

The other options describe different concepts. Experimenter bias is a broader term encompassing various forms of bias introduced by the researcher. The Hawthorne Effect refers to participants altering their behavior just because they know they are being observed, not specifically due to the researcher's expectations. Attrition relates to participants dropping out of a study and does not pertain to behavioral changes induced by expectations.