In the Land of the Blind: Applying a Single-blind Study to Finished Products

By: Johann W. Wiechers, PhD, JW Solutions

Posted: October 13, 2009

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The necessity for a single-blinded trial is that the placebo is different. To know that an active is active, a supplier must compare the active in a formulation to the same formulation without the active. This is called the placebo. Logically, to know that a formulation is active, one must compare the formulation to the same formulation without the formulation. But what is that—a formulation without a formulation? As this author has previously states, that is nothing. The investigator is testing against untreated skin.

Regulatory bodies claim that everything should be tested against a placebo, and many believe that “in proper science, you always test against a placebo.” The same regulatory bodies should also learn to see that there is a difference between fundamental science and applied science. In fundamental science, the question is whether an active is active and how it works. In applied science, the question is whether a formulation works. Finding out how much of the effect is caused by the active and how much by the formulation itself is fundamental science. Differentiating between fundamental science and applied science can be done by answering the question, “As a consumer, do I care?” A scientist would like to know what the effect is and why/how it is produced. A consumer wants a product to do what it is supposed to do. A consumer wants a car to drive, a CD to play music and a moisturizing cream to moisturize. Leaving personal interests of the individual consumer aside, a consumer does not care about the details of fuel combustion, the width of a laser beam or the stabilization of the orthorhombic phase of skin lipids. In such cases, a single-blind trial should be used because the subject in such a trial will always know whether he applied a product or not, or in case the subject serves as his own control, on which side of his body a product was applied.

Conducting a single-blind trail is wrong according to the regulatory bodies, who find that everything needs to be tested in a double-blind trial. Because otherwise, we will have the Clever Hans effect. Clever Hans was a horse that was claimed to have been able to perform arithmetic and other intellectual tasks. After formal investigation in 1907, psychologist Oskar Pfungst demonstrated that the horse was not actually performing these mental tasks, but was watching the reaction of his human observers. Pfungst discovered this artifact in the research methodology, wherein the horse was responding directly to involuntary cues in the body language of the human trainer, who had the ability to solve each problem. The trainer was entirely unaware that he was providing such cues. In honor of Pfungst's study, the anomalous artifact has since been referred to as the Clever Hans effect and has continued to be important knowledge in the observer-expectancy effect and later studies in animal cognition.

Can this happen in a single-blind clinical study? It can, but with Clever Hans, it took years of practice. It took years of social interaction to learn to read the signals from the trainer, and that was a Clever Hans. It took humans centuries to discover the effect, admittedly because it is subtle. But to address the question whether the Clever Hans effect happens in a single-blind clinical study, one has to realize that the reality of a clinical study is different. The investigator does not even know the subject and for them, the volunteer is nothing more than another test tube or something to measure a reaction on. There is no social interaction between the subject and the investigator. The professional evaluator is behaving as a professional and does not speak to the subject.  Social interaction is necessary for the Clever Hans effect, and that is lacking in clinical trials. If social interaction would happen once in a whole trial, that would be significant, but it cannot happen with every volunteer to explain the complete results. Volunteers are not trained, they are not horses, they are not clever and they are not called Hans. The latter, of course, may not be true.

Single-blind trails are possible and scientifically justified under specific conditions that frequently apply to the finished product manufacturer in the cosmetic industry. Some regulatory bodies understand this whereas others want a uniform response to whatever claim someone is trying to substantiate. Perhaps the regulatory bodies are double-blind. To those regulatory bodies, this author would like to say, "Wake up and stop closing your eyes for the reality of what the cosmetic industry is testing. Get off your Clever Hans horse and stop applying fundamental research principles to applied research. Open your eyes to the differences. Imagine how clever you would be if you would have an open mind towards different claims needing different study designs. You can be a single-eyed king called Hans or a double-blind Clever Hans stumbling in the dark. The choice is yours. As a cosmetic scientist with a visual impairment, I know which one I would prefer to be."