A researcher conducted a study to investigate the effects of smiling on helping behavior. Participants completed a survey that they thought was the purpose of the study, but in reality, the experiment...

A researcher conducted a study to investigate the effects of smiling on helping behavior. Participants completed a survey that they thought was the purpose of the study, but in reality, the experiment took place after they completed the survey. At the end of the survey session, half of the subjects were thanked with a smile and half were thanked without a smile. Whether the subject received a smile or not was randomly determined. The subjects then passed a confederate in the hallway on their way out of the lab who had just dropped a large stack of books. The number of subjects who helped the confederate pick up his books for the smile and no smile groups was compared.

1. What is the independent variable in this experiment? Is the independent variable manipulated between-subjects or within-subjects?

2. Can you think of an important ethical issue for this experiment and how to handle it in the procedure of the experiment?