Not long ago, people everywhere started to do the “finger game” on a first date. This is not as naughty as it sounds. As I describe in BLONDES, the finger game involves asking your companion for a look at his (or her) right hand. If his ring finger is longer than his index finger it’s a sign of prenatal exposure to high levels of testosterone. People with longer ring (than index) fingers are likelier to be more aggressive, better at sports, and more musically inclined. They may have more sex partners in life.

Now you can take the game to the next level: fingerprints.

Take a close look at the ridges on your companion’s fingers. (Actually, they’re best seen under a magnifying lens or photocopied and enlarged.) Most people have slightly more ridges on the fingers of one hand than the other.

More ridges on the right-hand fingers: This indicates higher levels of prenatal testosterone. He or she might master mental rotation – knowing which one of four abstract figures, revolved in three-dimensional mindspace, matches a diagram (a “masculine” task). Right-ridge dominant people are also better at aiming at a target and getting a bull’s eye.



More ridges on the left-hand fingers: This indicates lower levels of prenatal exposure. He or she may be a whiz at games like word associations, taking a word like clear and coming up with glass then Philip then opera then ghost, or naming as many round objects as she can in three minutes (considered “feminine” tasks). Compared to straight men, gay men have more ridges on their left pinkies and thumbs.

Four or more ridges on the fingers of one hand than the other: This reflects how much stress your companion weathered when he or she was a second-trimester fetus. For instance, researchers found that women who were 14-22 weeks pregnant when an epic ice storm hit Canada were more likely to have babies whose ridge counts varied greatly between hands. In nature, dramatic asymmetry is often a sign that the fetus has been stressed in some way. The more stress, the less symmetry. In fact, those with significantly asymmetric ridge counts between right and left hands were more likely to score lower in language and intellectual development as toddlers. Both fingerprint development and the brain may have been affected by constriction of blood flow to the placenta or stress hormone levels.

Other ridge count studies have also found interesting correlations: a significant difference between the ring and pinky fingers of the right hand is associated with less muscle mass in the lower extremities and a bulked-up upper body, including a thicker waist. A difference of around three or four more ridges between the thumb and pinky fingers is also associated with diabetes later in life. Asymmetries are also connected to cleft lip, dyslexia, schizophrenia, infections, and other prenatal problems.

Around ten weeks after conception is when the bottom (basal) layer of fetal skin outgrows the top (epidermis), and the tension between the two causes the skin to buckle. At this time fingerprints are like wet cement: any disturbance until mid- pregnancy may leave a lifelong impression. At this time the skin and the brain are both are made of the same raw material — fetal ectodermal tissue. Any disruptive event in the womb left its mark on both. This means that fingerprints give us clues about the brain.

You would like to know more about the minds of the people you date, which is why you’re analyzing their fingers. Of course if you could read their minds, you’d know they think you’re crazy.