What Does the Soul Weigh?

Editor’s note: This article was originally published on Paranormal People Online in 2013. It has been revised and updated for publication on The Curious Canadian. 

In the aftermath of a flurry of articles I’ve read recently about the problems researchers face when confronted with the vast mountains of information available through the internet, it seems particularly apt that I should happen upon the extraordinary story of the weight of the human soul.

Regular readers are aware of my growing obsession with the mind-body question: do humans have souls? The question has occupied philosophers since ancient Greece, and despite the passionate assertions of a great many people, it remains unanswered.

Outside of the sometimes highly satisfying philosophical ideas associated with this question, it seems that scientific investigation is the best way to determine whether there is any empirical basis for the existence of a soul. There has certainly been no shortage of ideas and research in this area over the past few decades, from Penrose and Hameroff’s Orch-OR theory of consciousness, to Ervin Laszlo’s Akashic Field Theory, to Parnia’s research through the AWARE Project. There’s no shortage of intriguing ideas to read about. 

One particularly intriguing feather in the cap of those who claim success in this area of study is the work that’s supposedly been done to weigh the human soul. This idea featured prominently in Dan Brown’s The Lost Symbol, which I quite enjoyed, even though it’s not his best work. Brown describes research conducted by the Institute of Noetic Sciences, though he gives the credit to his female protagonist, working alone on behalf of the Smithsonian Institution’s top-secret research division. He describes a highly sophisticated apparatus capable of precisely measuring the weight of people as they died. He gives no details regarding the results, however.

Fiction is fiction, of course, and Brown is famous for weaving enough fact into his stories to make the boundary between the two rather difficult to discern. In this case, as with others, the reality is considerably more complicated.

I found the concept—that the soul could actually be weighed—to be of great personal interest, and so I looked into it. It turns out there is a basis in fact here.

Beginning in 1901, Dr. Duncan MacDougall, a physician from Haverhill, Massachusetts, undertook an extraordinary experiment to determine whether the human soul had measurable weight. He placed six terminally ill patients on a specially constructed bed fitted to a large balance and attempted to measure any change in their weight at the moment of death.

From this experiment came the famous claim that the human soul weighs 21 grams. Contrary to the way the story is often told, however, 21 grams was not an average of MacDougall’s six subjects. It was the sudden loss he reported in his first patient. The results from the remaining patients were inconsistent, and some of the measurements were ultimately discarded.

MacDougall also conducted experiments on 15 dogs, none of which showed the same sudden loss of weight. He interpreted this as further support for his hypothesis. His work attracted considerable attention and was reported by The New York Times in 1907, before subsequently appearing in American Medicine and the Journal of the American Society for Psychical Research.

The problem is, that there were problems. MacDougall’s methodology was so questionable, and his results so inconsistent, that his experiment provided little in the way of reproducible evidence. And, since this was the turn of the 20th century we’re talking about, the available technology imposed limitations of its own. It stands, though, that MacDougall tried. What he did not establish was that the human body reliably loses a specific amount of weight at death, much less that any such loss could be attributed to a soul. It’s an easy jump from his results to believing the mind-body question answered, but the evidence simply doesn’t support it.

There was, however, another fascinating experiment taking place around the same period. Italian physiologist Angelo Mosso developed what he called the “human circulation balance”—essentially a delicately balanced bed capable of detecting changes in the distribution of a person’s weight. Mosso wasn’t actually trying to weigh the soul. Instead, he was investigating whether mental activity produced measurable physical changes in the body, including shifts in blood flow during cognitive effort. His experiments are sometimes drawn into the story of attempts to weigh the soul, but what he was really attempting to weigh, in a sense, was thought itself.

MacDougall’s and Mosso’s experiments were not, however, what Dan Brown was talking about. He may instead have been referring to a German study supposedly conducted in 1988 by two scientists named Becker Mertens and Elke Fisher. According to the story, Mertens and Fisher weighed some 200 terminally ill patients and found, universally, a difference of 1/3000th of an ounce between life and death. It seems the soul weighs roughly 0.01 grams. Their results were reportedly published in the German science magazine Horizons, and have since been widely cited as evidence that the soul exists.

Now, there would seem to be some methodological problems here too. Air leaving the patients’ lungs might account for some change in weight, as might other physiological processes occurring at or immediately following death. These and other criticisms have been levelled at this supposed experiment, as well as at MacDougall’s results.

There’s just one problem: I can find no convincing evidence that any of this actually happened.

The trail becomes particularly interesting thanks to an investigation by the writer behind The Tribal Scientist, who went looking for the original research. What he found—or, more importantly, failed to find—raises some serious questions. There appears to be no record of a German scientific journal called Horizon matching the one described in the story, no identifiable publication containing the supposed research, and no evidence he could find of scientists named Becker Mertens and Elke Fisher having conducted it.

That doesn’t quite justify the categorical statement that Mertens and Fisher never existed. Absence of evidence is not necessarily evidence of absence, particularly when dealing with names translated from another language and research supposedly conducted in East Germany in 1988. But an extraordinary scientific claim involving more than 200 human subjects should leave a trail. A paper, an institution, other publications by the researchers, citations, contemporary reporting—something. So far, that trail appears to lead nowhere.

Or, rather, almost nowhere.

The Tribal Scientist investigation traced what appears to be the source of the story to the Weekly World News, a publication considerably better known for sensational stories than scientific reporting. From there, however, the claim seems to have escaped into the wider world. It was repeated in New Dawn magazine and elsewhere online, accumulating the trappings of legitimate scientific research as it travelled.

And that, to me, is considerably more interesting than simply calling the story a hoax.

Somewhere along the way, an unsupported story became a “study.” The study acquired researchers, a scientific journal, experimental subjects, precise measurements and even criticism from other supposed experts. Later writers repeated those details, and repetition itself began to function as evidence. One source cited another, which cited another, until a reader encountering the story several generations removed from its apparent origin could be forgiven for assuming that somebody, somewhere, had checked whether the original research actually existed.

Apparently, very few people did.