Babies who had a lullaby played to them regularly while still in the womb recognized the song months after birth, a study has found.

The researchers had 10 expectant mothers play “Twinkle Twinkle Little Star” loudly multiple times per week throughout their last trimester of pregnancy. A few days after birth, they took electroencephalogram, or EEG, recordings of each newborn’s brain by using 12 electrodes scattered over different regions of the head.

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Upon hearing the lullaby again, they had significantly larger brain responses than a control group of newborns who had not been exposed to the song. The experiment was repeated after four months with similar results.

Study co-author and University of Helsinki psychologist Minna Huotilainen refers to this phenomenon as “preconscious learning.” The babies have no awareness of it – no “Oh, that old song from my intrauterine days” – but somehow their brains can still pick up on the fact that they have heard it before.

“They recognize the memory, and their brains react to it,” said study co-author Eino Partanen, also a University of Helsinki psychologist. “But do we mean memory like how we have in adults? No. This is more like familiarity.”

Also, the scientists found that the more times a mother played the recording for her unborn child, the stronger the electrical signal from the baby’s brain would be.

When the researchers played a modified version of “Twinkle Twinkle Little Star,” the babies seemed to notice when that was amiss. The EEG was fast enough to catch note-by-note neural responses, and when a wrong note was played, their brains would react differently.

“It is a matter of noticing a difference between what you hear and what you should be hearing,” Partanen said. “Memory plays a part in that.”

The study was published online Wednesday in the journal PLOS One.

“It’s plausible since late-term fetuses display the full repertoire of abilities that newborns have,” said Johns Hopkins University developmental psychologist Janet DiPietro, who was not involved in the research. “They can both learn.”