The idea of accessing not only the control of people but also of the information they might be hiding is so attractive that the concept of “truth serum” has become very popular and well known .

It has been presented as a liquid whose potential to achieve perverse ends is difficult to imagine at all, and with effects as simple as its method of use: someone is made to drink it, and shortly afterwards an interrogation begins in which what we hear will correspond entirely to what the person being questioned believes he knows reliably. The option to lie will have disappeared.

Representations of truth serum seem idealized in works of fiction such as Harry Potter (under the name of Veritaserum), but in real life it has also been a substance used, especially by intelligence services, in its variant of sodium pentothal . Now, do these kinds of substances really work?

The story of truth serum

At the beginning of the 20th century, news spread that scopolamine, also known as burundanga, a substance that was administered to women to help them endure the pain of childbirth, made them much more uninhibited and they began to talk about intimate details of their lives with people they did not know.

In the absence of a cognitive psychology and a scientific perspective based on the neurosciences, it was psychoanalysis, the dominant paradigm at that time when talking about mental processes, that was responsible for offering an explanation of how this truth serum worked.

Using the ego structures of the psyche, it was proposed that certain substances, when entering the organism, made the Ego neutralised and therefore could not repress the forces coming from the Ego , so that neither morality nor the expectations of not “getting into trouble” were a barrier for a good part of the person’s most intimate thoughts to emerge to the surface.

It was later, when it became known how psychotropic drugs work, that one began to intuit what the mechanism of functioning of truth serums is… and why they are ineffective.

Entering the nervous system

Basically, truth serums like sodium pentothal are central nervous system depressants. This means that, because of their chemical composition, they make various parts of the brain less active and therefore the executive processes related to how we control where our focus of attention goes and what kind of actions we should avoid are relaxed, as if they let our guard down.

This means that there are virtually no significant differences between, for example, sodium pentothal and any other hypnotic drug, in that its characteristic effect is drowsiness, sedation and altered states of consciousness .

Seen in this way, it makes sense that it produces disinhibition in the content of what is said, because with that substance circulating in the brain it is practically impossible to take into account what kind of things are not appropriate in a given context, the networks of neurons that work together creating our thoughts are so numb that they cannot perform several complex actions at the same time, such as the evocation of an idea and at the same time the need not to say it.

Sodium Pentothal and True Confessions

But what theoretically characterizes the truth serum is not simply disinhibition, but the truth of the content of what is said. In that sense, both sodium pentothal and similar barbiturates fail miserably.

Why? Among other things because a truth serum is a psychopharmaceutical , and as it is not an intelligent entity; it simply circulates through our organism by attaching itself where its chemical characteristics allow it and passing by (or transforming itself into other components) in the rest of the cases.

That means that it has no way of detecting neurochemical processes specifically related to truth, it just “fits” into certain slots, for better or for worse. This is also why sodium pentothal, like any drug, not only produces the expected effect that the doctor or the military man who is supplying it is trying to achieve, but also generates several side effects of greater or lesser intensity .

In the case of pentothal, this substance is coupled to various receptors of a neurotransmitter called GABA, which is a depressant of brain activity, and acts by imitating it, which means that it reinforces the effects of a substance that is already present in our body. The consequence of this is that we enter a state of drowsiness in which “everything is the same” and in which factors such as social norms and concern for the image that is being given lose a good part of their importance .

The most absurd interrogations

In conclusion, the use of truth serum, besides being unethical as such, can at most serve to make the respondent start talking inconsistently, without paying attention to whether what he says is true or not.

The defenses that separate his thoughts and what he says may be relaxed , but it will also be true that the quality of his thoughts, in terms of their relationship to reality, will have plummeted.