Does the length of your fingers predict sexual orientation?

Imagine my surprise last week when I saw an article in Science that claimed "finger lengths can predict personality and health."* Huh?

The author, science writer Mitch Leslie, gives us the rather startling number that over the past 20 years, more than 1400 papers have been published linking finger lengths to personality, sexual orientation, cardiovascular disease, cancer, and more.

What is this magical finger length ratio? Simple: it's the ratio between the lengths of your index (2nd) and ring (4th) fingers, also called the 2D:4D ratio. Take a look: is your index finger longer than your ring finger?

It turns out that most people have slightly longer ring fingers than index fingers, and in men the difference is a bit larger. If the ringer finger is longer, than the 2D:4D ratio is less than one. One recent study reported that this ratio was 0.947 in men and 0.965 in women. Another study found average values of 0.984 and 0.994 for men and women. Not only is this a tiny difference, but in every study, the 2D:4D ratio among men and women overlapped, meaning the number alone doesn't tell you very much.

Nonetheless, some researchers have taken this tiny physiological difference and run with it. Nearly 20 years ago, Berkeley psychologist Marc Breedlove (now at Michigan State) published a study in Nature where he and his colleagues measured finger-length ratios in 720 adults in San Francisco. Based on this data, they concluded that finger-length ratios show

"evidence that homosexual women are exposed to more prenatal androgen than heterosexual women are; also, men with more than one older brother, who are more likely than first-born males to be homosexual in adulthood, are exposed to more prenatal androgen than eldest sons."

Whoa! They are not only claiming that the 2D:4D ratio is predictive of homosexuality, but also that exposure to prenatal androgen is the root cause of both finger lengths and sexual orientation. (Confusing correlation with causation, perhaps?) Not surprisingly, this claim is not widely accepted.

There are many, many more claims out there. In 2010, the BBC boldly reported that 

“The length of a man's fingers can provide clues to his risk of prostate cancer, according to new research.”

based on this study in the British Journal of Cancer. That study found that men whose index fingers were longer than their ring fingers had a reduced risk of cancer. (I don't believe it for a second, but if it makes you feel better, go ahead.) And a 2016 report found that both men and women with a low 2D:4D ratio (longer ring fingers) had better athletic abilities. 

The Science article goes on to explain, though, that "the results often can't be replicated." Most of these studies are small, the measurement techniques vary widely, and efforts to reproduce them (when others have tried, which isn't that often) usually fail. It didn't take me long to find a few, such as this study from 2012, which swas the 2nd failure to replicate a result claiming a link between sex hormone exposure and the 2D:4D ratio.

The author's left hand

After reading the whole Science article, one comes away with the impression that finger ratio science is almost certainly bogus. The presentation, though, gives far more space to the claims of those who believe in it, and one gets the strong impression that the journalist (Mitch Leslie) is on their side. A hint to that is in his last sentence where, after saying that the two sides are "talking past one another," he writes "more than 20 papers using the digit ratio have already come out last year."

And since the last sentence is often a giveaway for what the writer really thinks, let me conclude by saying that both my ring fingers are longer than my index fingers.

[*The print version of Science contains precisely this claim in the subheading to the article: "Some researchers say a simple ratio of finger lengths can predict personality and health." Interestingly, the online version of the same article does not have this headline. Instead, it reads "Scientists try to debunk idea that finger length can reveal personality and health." It appears as if the online editors were more skeptical than the print editors.]

Google ran a secret experiment to search for cold fusion. Did they find it?

A non-working cold fusion apparatus

at the San Diego Naval Warfare 

Center. Source: Wikipedia

The journal Nature last week revealed the results of a 4-year, $10 million experiment to test cold fusion. The experiments were kept secret in order to avoid the negative publicity that cold fusion attracted when it burst upon the scene 30 years ago.

I've been talking to a few non-scientists about this, and it appears that many people don't know about the cold fusion saga, so here's a quick recap: back in 1989, two chemists at the University of Utah, Stanley Pons and Martin Fleischmann, held a press conference to announce a startling discovery: they had generated fusion energy at room temperature. If true, this would have been a profound, civilization-changing discovery: cold fusion had the potential to provide nearly free energy to the entire world, eliminating our dependence on fossil fuels and promising unheard-of economic and environmental benefits.

[A physics aside for those who might be curious: fusion energy is produced when two atoms are smashed together to form a new, heavier atom. Four hydrogen atoms can be fused to form one helium atom, for example. A tiny bit of mass is converted to energy in the process, and that tiny amount produces enormous amounts of energy, as given by Einstein's famous equation, E=MC². Fusion is the process that powers the sun and other stars, but humans have never been able to control it. It's also the source of the energy released by a thermonuclear bomb. The only nuclear energy we humans can control is fission, which is what nuclear power plants use. And the only fusion we know about requires crazily high temperatures, which is why room temperature would be "cold."]

Unfortunately for Pons and Fleischmann, whose reputations were forever tarnished, the 1989 experiments were fatally flawed. Many scientists tried to reproduce the results, but they all failed, and the criticism mounted quickly. Pons and Fleischmann never published their findings, and cold fusion later became a meme for flawed or impossible scientific results. Even today, calling something "cold fusion" is form of ridicule.

Despite the dramatic failure 30 years ago, cold fusion isn't fundamentally impossible, unlike homeopathy, acupuncture, reiki, or other forms of pseudoscience. Fusion is a very real phenomenon, and no one really knows if it might be possible to sustain a fusion reaction at low temperatures, or what those temperature limits might be. This is what led Google and the scientific team they funded to give cold fusion another serious look.

The new Google-funded experiments were run by a team of about 30 graduate students, postdoctoral fellows, and professors. The seven leaders of the team, who include scientists from UBC, MIT, the University of Maryland, LBL, and Google, described their findings in a paper just published in Nature. After four years of careful experiments, they conclude:

"So far, we have found no evidence of anomalous effects claimed by proponents of cold fusion."

In other words, they couldn't get cold fusion to work. They tried 3 different experimental setups that have been proposed by others, but despite their best efforts, nothing produced any signs of fusion energy.

The news isn't all negative. The scientists emphasized that in the course of trying to produce cold fusion, they had to design new instrumentation and study new types of materials that have received little attention before now. They wrote:

"... evaluating cold fusion led our programme to study materials and phenomena that we otherwise might not have considered. We set out looking for cold fusion, and instead benefited contemporary research topics in unexpected ways."

They cite go on to say:

"Finding breakthroughs requires risk taking, and we contend that revisiting cold fusion is a risk worth taking."

I have to agree with them here. As the scientists themselves pointed out, even though their experiments didn't produce cold fusion, "this exploration of matter far from equilibrium is likely to have a substantial impact on future energy technologies." In other words, if we keep trying, who knows what we might find?