Testosterone therapy may help keep men looking younger, but could it also change their disposition? Perhaps. A finger study proves testosterone may be the culprit behind men’s insensitive ways. The length of a person’s index finger as opposed to their ring finger (the second and fourth digit) can be a telltale indicator of prenatal exposure to the male hormone testosterone. According to the BBC, “On average, women’s index and ring fingers are almost equal in length because they are exposed to less testosterone. In men, the ring finger tends to be longer because they have higher testosterone levels. In general, women exposed to more testosterone have more ‘masculine hands’ – i.e. longer ring.”
Testosterone levels appear to contribute to the inability to identify and read facial expressions. This inability to gauge the emotions of others is also a major symptom of autism.
This study examined whether young females who took oral doses of testosterone would be able to read facial expressions. The experiment involved giving female volunteers ages 20 to 25 testosterone in the first phase and a placebo in the second. The volunteers took a computerized test called “reading the mind in the eyes (RMET)” where they described the expression of pictures of people shown one at a time.
The women who were given testosterone instead of the placebo showed a decrease in their ability to identify expressions. More importantly, the inability to identify expressions was higher in women who had shorter index fingers than ring fingers — the signal of fetal exposure to testosterone and by extension an indicator of autism.
A similar study involving the female hormone oxytocin that was given to healthy young males and males with autism showed improvement among both groups in recognition of facial expressions. The authors conclude that further studies looking at the role of male and female hormones in the development of autism are needed.
The authors’ findings about testosterone also suggest an underlying reason why autism is primarily a disorder found among males.