Babies cry to call attention to their immediate needs: food, or rest, or a diaper change or cuddles. But without intending to, wailing babies might also provide insight into a defining trait that will develop later in life. As Matt Stevens of the New York Times reports, a new study has found that the pitch of a baby’s cry could predict what he or she will sound like as an adult.
The authors of the study, which was published recently in Biology Letters, hoped to build on previous research showing that vocal pitch in seven-year-old boys could predict 64 percent of the differences in vocal pitch among adult men. What an adult will sound like, in other words, may be determined before puberty, a time when our voices often begin to change discernibly. Researchers in the U.K. and France wondered if vocal pitch might be determined even earlier than age seven—during infancy, perhaps, or even in utero.
To find out, the team recorded the cries of 15 French babies—six girls and nine boys, from two to five months old. Researchers then compared those recordings to recordings of the same children at age four or five. The team found that the pitch of babies’ cries were a “substantial predictor” of vocal pitch at four or five years of age. Differences in voice pitch, the researchers conclude, “may—at least partly—arise very early in life.”
The study authors posit, in fact, that these differences might develop in the womb, when fetuses are exposed to varying levels of hormones.
“In utero, you have a lot of different things that can alter and impact your life — not only as a baby, but also at an adult stage,” Nicolas Mathevon, a professor at the University of Lyon in France and one of the authors of the study, told the NYT.
As Carl Engelking of Discover reports, the team also analyzed the children’s 2D:4D digit ratio, or the ratio between the lengths of the index finger and the ring finger. Studies have suggested that this ratio can reveal how much testosterone a person was exposed to in utero.
“If your index finger is shorter than your ring finger, you may have been exposed to more testosterone in the womb,” Engelking explains. “If your index finger is longer than your ring finger, you may have been exposed to lower levels of testosterone. The ratio is a supposed predictor of masculine traits later in life (more testosterone=more masculine traits).”
Researchers found that 2D:4D digit ratio in the right hand correlated positively with differences in vocal frequency in both baby cries and children’s speech (this is consistent with other studies showing that 2D:4D ratios are expressed more strongly in the right hand). In other words, as a statement announcing the new research explains, “if the index finger on the right hand is longer than the ring finger, a baby will likely to grow up to have a high-pitched voice. Conversely, if it is shorter, they will be more likely to have a lower-pitch voice.”
“This explains a lot, but not all,” Mathevon told the Times. “It’s only half the story I would say.”
Though the team’s findings are intriguing, there are significant caveats to the study. The sample size, for one, was very small; researchers analyzed the voices of just 15 children, all of whom lived in France. Boys were also overrepresented in the study.
Moving forward, the team hopes to continue its line of research with a larger sample size that includes more girls and children from diverse backgrounds.