In one research project, a scientist gave students subliminal cassette tapes and told them to play them for 2 months. after 2 months, she assessed whether the tapes helped the self-esteem of her participants and found that self-esteem had indeed risen! while she may have attributed this to the tapes, it is also possible that those students may have found college life to be manageable and thus experienced an increase in self-esteem for that reason. this demonstrates which principle of critical thinking?