By definition, a placebo has no biological effect. Therefore, besides classical non-specific effects, the outcome associated to a placebo rests on its “meaning”. Meaning is always for someone and understanding the effects attributed to placebo requires to describe the expectations and interpretations of the agents involved in the experiment.
We present a probabilistic modeling of the “placebo effect” that has its roots in the act of measuring and – in contrast with other hypotheses such as patient’s expectation or conditioning – is centered on experimenters and not only on patients. Therefore, this modeling potentially applies to any biology experiment aimed to demonstrate a causal relationship. Its originality is the description of the experimental situation from the point of view of an uninvolved participant who does not interact with the experimenters and the biological system.
When probability fluctuations inherent to any measurement are taken into account, a counterintuitive result emerges: two placebos with different “meanings” can be associated with different “effects” after measurement of a biological system. In clinical trials, this “meaning effect” due to the experimenters could add to the drug effect and contribute to the “placebo effect”.
This simple modeling suggests that the act of measuring is not always neutral and some correlations between apparent causes and observed outcomes may emerge, thus contributing to conclude for obvious – but false – causal relationship. These results could have consequences in the design and interpretation of experiments in life sciences, medicine and psychology.
|