Which research method involves manipulating variables to observe effects on behavior?

The correct answer is the research method known as an experiment. In an experimental setting, researchers systematically manipulate one or more independent variables to assess their impact on dependent variables, which reflect behavioral outcomes. This approach allows for the establishment of cause-and-effect relationships, as it provides the ability to control for extraneous variables and isolate the effects of the manipulated variable.

For instance, if a researcher wanted to determine whether a particular type of incentive increases productivity in a work environment, they could set up an experiment where one group receives a specific incentive and the other does not. By comparing the productivity levels of these two groups, the researcher can draw conclusions regarding the causal relationship between the incentive and productivity.

Other research methods, like case studies, surveys, and longitudinal studies, serve different purposes. Case studies involve an in-depth examination of a single subject or group, which can provide rich qualitative data but does not manipulate variables in a controlled manner. Surveys gather self-reported data from participants, primarily focusing on attitudes or opinions rather than directly assessing behavioral changes through manipulation. Longitudinal studies track the same subjects over an extended period to observe changes over time but do not involve the manipulation of variables to understand specific effects. Thus, while these methods are valuable for qualitative insights or descriptive