The notion that there exists a correlation between the length of a person’s finger and their amicability may seem strange. However, researchers from McGill University are showing exactly that—but only in men. Scientists, by comparing the length of the index second finger (2D) to the fourth finger (4D), have created a reproducible standard for predicting behaviours in people known as the 2D:4D ratio.

“Men with smaller 2D:4D ratios were more likely to engage in behaviours such as listening attentively, smiling, compromising, expressing reassurance and complimenting the other person,” explained Professor Debbie Moskowitz, lead author of the study.

A person’s level of amiability can be made into a single mean by evaluating their reactions throughout the day, explained professor emeritus, Dr. Simon Young, a co-author on the study.

“[Moskowitz] had developed a pretty nice method for looking at human social behaviour in everyday life,” Simon said. “People would check off various interactions that they had engaged in throughout the day.”

For this study, Moskowitz and her colleagues studied 155 men and women over the course of 20 days and had them complete evaluation forms. From this data, Moskowitz was able to compile two major axes: Dominant or submissive, and agreeable or quarrelsome. The participant’s overall behaviour could then be averaged into one category. The team found that these character traits were directly correlated to the 2D:4D ratio.

“The ratio of index finger to your ring finger for the 2D:4D ratio is related to testosterone exposure in utero,” explained Simon.

Digit ratio has been shown to be determined by the amount of testosterone that the fetus was exposed to during development. According to past studies, it is highly likely that these same hormones affect development of the brain, which could account for the differences in behavior. Men with smaller 2D:4D ratios have had higher levels of hormone exposure, and were more likely to act agreeably with women, while the men with larger 2D:4D ratios had lower hormone exposure in utero, and were also more quarrelsome.

“It gives this neat marker of what happened when an adult’s brain was developing,” Simon said.

Other studies have shown that correlations exist between the 2D:4D ratio and the number of children a person will have, whether a person would be monogamous or not, and a person’s risk of developing cancer. Interestingly, these effects are absent in women.

These results come as no surprise to the researchers and add to the ever-growing list of literature that relates digit ratio with behavioural and physical traits.

“It’s interesting from two points of view,” Young said. “First of all, what is happening in the fetal brain can program the adult in this extremely specific way. And the second thing is human social interaction. This is just one more little piece in the puzzle of the factors influencing it, which we really need to know more about.”

Two vaccines currently exist to protect against HPV. Cervarix is a “bivalent” vaccine, meaning that it contains viral antigens against two strains of HPV. It protects against the two most common cancer-causing strains, HPV-16, and 18, whereas “quadrivalent” Gardasil protects against four strains, HPV-6, 11, 16 and 18. Unfortunately, these aren’t the only strains that can cause cancer, and optimizing viral protection is key.

In a recent paper in the New England Journal of Medicine a new vaccine—Gardasil 9—offers protection against the original four strains, as well as HPV-31, 33, 45, 52, and 58—making it nine-valent. When conducting clinical trials, this new vaccine showed a 20 per cent increase in protection against genital cancers in women between the ages of 16 and 26.

While Gardasil 9 is associated with an increase in side effects from using the vaccine compared to its counterparts, the cancers that the vaccine protect against are not comparably dangerous. These side effects are expected due to the fact that the new vaccine has more viral antigens. The side effects include headaches, nausea, dizziness, and fatigue.

Despite the assumption that only women should be vaccinated for HPV, in reality, it is highly recommended that HPV vaccines be administered to men and women. Men who have sex with other men and have not been vaccinated are also at risk from HPV-related diseases. Vaccinations contribute to protecting everyone, explained Dan Apter, lead author on the study.