Placebo effects are mostly discussed in the context of medical treatments, and refer to clinical improvements or perceived improvements that cannot be attributed to the action of any medical intervention. Placebo effects can be elicited by administering of sugar pills, conducting sham surgeries, or by inactivating medical equipment without informing the patient. The types of response that can be elicited by placebos is subject to some dispute, but is generally acknowledged to be largely limited to symptoms that are substantially psychological in nature, such as pain, nausea, discomfort, stress, depression, anxiety, itchiness, etc. Placebo effects are a complex psychological phenomena, but are generally thought to be the result of expectation effects – people expect that treatments will help their symptoms, and therefore as a result of this expectation they come to actually experience an improvement in their symptoms. It is important to understand that the placebo effect is not the result of people being ‘fooled’ or some mystical power of ‘mind over matter’, as some have claimed. Rather, placebo effects refer to a broad class of improvements or perceived improvements that have a psychological rather than a medical or pharmacological basis.
The Hawthorne effect is a related phenomenon most relevant to psychological studies and social or business interventions. In essence, the effect refers to the observation that changes to a workplace environment or other such setting can result in short-term increases in performance totally independently of what is actually changed. That is, initiatives to improve the office work environment often elicit a short term improvement in productivity regardless of what the improvement is. A number of explanations have been put forward to explain this result, including that workers work more efficiently when they feel they are under closer scrutiny, that morale improves when workers feel that others care about improving their conditions, that workers may develop an expectation that the reforms will improve productivity and so may subconsciously improve their performance as a result, or that workers may be enthused and energised for a time as a result of the novelty of whatever changes are made. Whatever the precise explanation, the key fact is that interventions can have a beneficial effect on performance totally independently of whether the intervention is actually performance-enhancing for the reasons originally anticipated. The mere act of making some change and observing the result can often have a positive effect by itself.
Both of these phenomena, the placebo and the Hawthorne effect, necessitate that good quality studies be controlled, meaning that the study population is divided into two or more groups. One group, the treatment group, is given the real intervention, which could be the real drug, the actual operation, a functioning device, the correct workplace reform, etc. The other group, the control group, is given a fake intervention, which could be an inert sugar pill, a sham operation, a non-functional device, a non-substantive workplace reform, etc. The results of the study are then determined by comparing the difference between the experimental and control groups. Failure to include a control group, and instead comparing the treatment group to some external standard or baseline, fails to account for the effect of the placebo and/or Hawthorne effects, and as such can lead to inaccurate results. Ideally, a controlled study should also be blinded, meaning that experimental subjects or participants do not know whether they are in the treatment or the control group, though sometimes this is not feasible. In a double-blinded study, neither the participants nor the experimenters themselves know which is the control and which is the treatment group (e.g. doctors administering the medication do not know whether it is an active pill or a sugar pill), which can prevent subtle but well-documented effects of experimenters influencing the behaviour or outcomes of the subjects.
Placebo effect: very useful and nuanced discussion of the importance and effects of placebo effects in a medical context
What is a placebo: useful background information from a medical context
Double blind experiment: a straightforward explanation of the importance of blinding in research
The Hawthorne, Pygmalion, Placebo and other effects of expectation: informative if somewhat disorganised set of notes and links related to these topics
Experimenter effect: a discussion of experimenter bias from the Skeptic’s Dictionary