The Man Who Measured The Weight of a Soul

People have tried to photograph souls (in this case, the Brown Lady of Raynham Hall, the most famous alleged ghost photo)  but only one guy tried to weight them.

People have tried to photograph souls (in this case, the Brown Lady of Raynham Hall, the most famous alleged ghost photo) but only one guy tried to weight them.

Humans have long believed that something in them survives death (although some afterlives are weirder than others.) Although this entity has gone under many names over the centuries, the one that most people in the West are familiar with is “the soul.” Most people take it on faith that a thing called a soul exists. This essential essence of human beings is said to be without substance, a part of another plane of existence that is temporarily wrapped in a body of flesh and bone before returning from where it came.

But for some, that is not enough. In a world of materialism, where we understand more and more how the world functions in a measurable and verifiable way, the existence of a thing without substance that is supposedly responsible for all of the functions of the human mind is a big pill to swallow. After all, many things that people took for supernatural in previous centuries have since been proven to work according to measurable, physical processes. No supernatural explanation required.

This demand for a tangible model of the soul inspired a very odd experiment performed in 1907. Dr. Duncan MacDougall, of Haverhill, Massachuesetts, believed that the soul had physical substance. And he set out to find its exact mass by measuring the weight of patients at the moment of death.


Dr. MacDougall’s soul weighing apparatus

In order to perform his odd experiments, Dr. MacDougall built a specially made scale. The dying patient would be laid on one side, which was a hospital bed rigged to the apparatus, and the other side would be weighted to balance out the patient’s weight.  Dr. MacDougall reasoned that if the soul had substance, it must have mass, and thus that loss of mass could be measured.

MacDougall performed his experiment on six human patents and fifteen dogs. In the human patients, more than one case showed a drop in weight, about 3/4 of an ounce or about 21 grams. The dogs showed no drop in weight, confirming MacDougall’s belief that animals did not have souls.

It seems cut and dry, but there were some very serious flaws with MacDougall’s methods.


A flawed method births a cultural meme

The biggest flaw of the soul weighing experiment was the small sample size. Only six data points is not really enough to pull a general conclusion from. Besides that, of the six people he experimented on, only a handful showed any results. He had to throw out two cases outright. One died before he could finish adjusting the balance of the apparatus, while in the second discarded case the measurements were interrupted by hospital staff who weren’t happy with the doctor’s macabre experiments. One patient showed a drop immediately after death. Two more showed a drop in weight that increased with time, while another showed a drop in weight that decreased and then increased again. Another showed a drop in weight, but after a slight delay, which MacDougall attributed to his dull wits. The poor soul apparently was too dumb to know it was in a dead body and hung around a bit before realizing it could leave (I’m paraphrasing, of course.)

Put short, the results were too inconsistent to draw any conclusions from. If MacDougall had access to a larger sample size and better equipment, his data would have been more convicting. But since his data set was tiny and his equipment cumbersome, so his findings are dubious at best.

In MacDougalls defense, he did try to explain some of the variables. He and some fellow doctors involved in the study tested whether the release of the final breath at death might account for a loss in weight. They did this by laying on the scales and, after they were balanced, taking deep breaths and blowing them out forcefully. The scales didn’t register any change.

But probably the biggest flaw in the whole experiment had little to do with the apparatus or the sample size. MacDougall and his fellow experimenters didn’t have a way to accurately determine the time of death, which is pretty important if you believe the soul departs right after that point.

The experiment was reported on in the New York Times, but other than that it made few waves. Most scientists recognized the flawed methods and roundly criticized the work. There is no evidence that MacDougall performed any other similar experiments. Or, if he did, he found no notable results. He died in 1920, a fairly obscure figure by that point. His experiment lives on in the zeitgeist though. The experiment is held by some as a proof for a soul, and the weight of 21 grams inspired a 2003 movie by that name.

To date, no one has again seriously attempted to measure the soul. The issue of the soul’s existence remains, as it ever was, an issue of faith.



“Soul has Weight, Physician Thinks.” The New York Times. March 11, 1907

“Soul Man.” April 24, 2013. March 7, 2014. <>