The Double-Blind Study
Humans are biased creatures. We tend to believe the things we want to believe and are influenced by
feelings rather than facts in many situations. There’s nothing wrong with that most of the time. It
certainly gives thousands of psychologists, anthropologists, and sociologists fascinating cases to study.
But sometimes, we need to know things for certain – untainted by our opinions, experiences, and
Scientists struggled with this problem for years. But, in 1784, a group of French scientists caught on to
something. They developed a “blind experiment” meant to find out whether a group of mesmerists
could identify objects that were once filled with vital fluids. They couldn’t. This provided two important
insights: first, people helped by mesmerists only improved in heath because they believed the
mesmerists could truly help them (later known as the
placebo effect); second, keeping vital information from
subjects of tests can help reduce bias.
From there, blind experiments continued to progress and
develop. In 1799 a British scientist exposed one group of
people to laughing gas and another to oxygen. He didn’t
tell the participants which group they were in and was
able to measure the actual effects of laughing gas with
exceptionally reduced bias or underlying psychological
By the mid-20th
century, a double-blind method was finally developed. The theory behind a double-blind
experiment is that the scientist may also hold biases and either see evidence that is not really there, or
interpret findings based on his/her preconceptions and pre-existing theories. So, early double-blind
experiments used blind administrators as well as subjects. An un-informed administrator would gather
results, not knowing what the end goal or aim was.
The First Double-Blind Experiment
For example, the first double-blind experiment dealt with the effects of substances in drinks (coffee,
alcohol, tea, etc.) on both the physiology and psychology of the partaker. In this case, he acted as both
the subject and theorizer. He drank the substances but insisted that they be disguised so he would not
know if he was drinking a drug or a control. He then recorded the data and later found out what caused
what. Since then, double blind experiments have been commonly used to add more reliability to the
analysis of scientific data gained through experimentation.
From large scientific centers in Heidelberg, Germany to clinical research centers in Utah, double blind
studies have proven very effective methods for testing theories and gathering pure data. These tests
have helped the quality of research from everything from medicine to physics to forensics.
Recently, there have been calls for double-blind procedures in police photo lineup identifications.
Witnesses are shown multiple pictures and asked to pick out the actual suspect. This is to test their
memory and confirm the identity of the accused. However, subtle movements, actions, or particular
treatment of photographs by the administrating officer may bias witness towards or against the correct
photo. As such, not informing the officer or witness of which person is the accused would add validity
and fairness to the process.
Click here to learn more about more interesting double-blind experiments!