Repeated exposure to a person or situation will cause memory for specific instances to fade, making it difficult to recall details of any one episode. This can be problematic, but it can also be seen as a good thing. In what way does this process benefit us?

Martha participates in a research study in order to receive extra credit for her psychology class. when she arrives in the research office she is given a can of what looks and tastes like beer, but which actually contains no alcohol. in the adjoining room martha's classmate karen is also participating in the study. karen receives a can of alcoholic beer. if the experiment was designed to test the effects of alcohol on concentration, then who is exposed to the independent variable?