2018-07-11-325.md

layout	title	byline	doi	tags	summary
post	The pitch of babies’ cries predicts their voice pitch at age 5	Levrero et al	10.1098/rsbl.2018.0065	humans cry voice acoustics audio auditory sound baby development fundamental-frequency voice-pitch gender	The pitch of a baby's cries and the ratio of its finger lengths is predictive of voice fundamental frequency later in life.

The fundamental frequency ($F_0$) of a human's voice is a key attribute that we use to distinguish individuals. And naturally, it is a key indicator of an individual's age and (often) gender.

That humans can learn so much about an individual's demographics just from sound alone is pretty remarkable: Imagine if I told you a bird could determine another bird's age just from its chirps. It'd sound pretty impressive! (Well... I guess imagine that I told you that before the previous paragraph.)

With a relatively small cohort population (n=15), the researchers were able to explain 41% of the variance of $F_0$ of five-year-olds using only the pitch of their cries as 4-month-olds. In other words, knowing the pitch of a 4-month-old's cries is predictive (as per the title of this paper) of their voice fundamental frequency at age 5.

It's not clear yet (since the data can only be collected at a rate of one year per year, duh) if this is predictive of $F_0$ later in life as well. But... Probably, right?

Prior research has suggested that the ratio of lengths of index finger and ring finger on the right hand correlate closely with the amount of testosterone available to the fetus in-utero, and so it would make sense that $F_0$ correlates with this ratio (the 2D:4D ratio) as well. And sure enough, the researchers found that the right hand 2D:4D ratio correlated with both baby cry pitch and 5yo fundamental frequency. Bizarrely (or at least unexpected to me), left hand 2D:4D ratios exhibited far more noisy correlations.