Robert was listening to the instructions provided by his boss. however, it was difficult to hear each step because caitlin and josh were engaged in a discussion close by. which barrier to effective listening is hindering robert's ability to listen to his boss?

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?