If you are conducting an experiment in which you give participants a pill that is aimed at stress relief, the patients might tell you they do not feel as much stress after taking the pill for 3 weeks. This however, does not mean the pill reduced their stress levels. The patients reduced stress could be caused by their expectations that the pill would reduce their stress. This concept is called the placebo effect, meaning the patients improved their condition because they knew what the pill was supposed to do for them. Using this knowledge is using the correlation vs. causation principle of critical thinking because, although there was a correlation between the pill and reduced stress, the pill is not what caused the reduced stress.The placebo effect is extremely important to studying psychology because whenever you are trying to analyze results of an experiment, you must consider the placebo effect. Your results cannot be valid unless you have accounted for the placebo effect by making the experiment blind (patients do not know if they are receiving the placebo or real medication). When I was younger my mom would always give me a Seven Up when i was sick and told me it would make me feel better. After I drank the Seven Up I would begin to feel better. Although there may have been some truth to this, I never accounted for the placebo effect in this situation. The main reason I would begin to feel better was probably because I thought I would feel better after drinking the Seven Up. Here is another example of the placebo effect on students who think they are drinking alcohol: http://depletedcranium.com/my-favorite-example-of-the-placebo-effect/ which can also be seen below.
I still wonder what goes on inside our body to actually make us feel better if the pill we take does not scientifically help us. How does believing a pill will improve someones depression lead to that person becoming less depressed?