Love spicy food? Find certain songs calming? You started developing preferences for flavours and sounds while you were still in the womb. And it’s not just us: many animals begin learning about the world around them before they’re even born.
Listening from the inside
Before you were born, you had a lot to listen to. There was the regular thumping of your mother’s heart, the blood whooshing through her body, and even the rumbling and gurgling of her stomach. You were also getting to know your mother’s voice and from the moment you were born, you preferred her voice over a stranger’s. What’s more, you already preferred listening to your mother’s native language over other languages.
You may have developed more specific preferences too. If your mum liked listening to a particular song or type of music, you would have recognised it and liked it too. One striking example of this comes from a study of women who watched the Australian soap opera Neighbours daily during their pregnancy. Four or five days after birth, babies who had heard the muffled strains of the show’s theme song before they were born became immediately calm upon hearing the song again. The song had no such effect on babies who hadn’t heard the song before birth. The same has been shown for babies who frequently hear particular nursery rhymes before birth.
Other studies have shown we learn words and sounds in the womb and that the memory of these sounds can be detected in our brains. The melody of our newborn cries have characteristics of our native language, and if your mum spoke multiple languages during her pregnancy with you, you were born liking the sound of each of the languages you were exposed to.
A taste sensation
It’s not only sound we’re exposed to in the womb: we also learn about flavour. Before you were born, you swallowed the amniotic fluid that surrounded you. And this fluid bore the signature flavours of the food your mother ate. If she ate spicy food, you developed a taste for it too. We know a variety of flavours can be easily detected in amniotic fluid, including garlic, mint, aniseed and vanilla. One study showed that mothers who ate lots of garlic during pregnancy gave birth to babies who also liked garlic. Babies who aren’t exposed to garlic before birth generally hate the flavour. The same goes for carrots: mothers who drank carrot juice during the last few months of pregnancy had babies who went on to happily eat carrot and carrot-flavoured cereal. So if you want kids who’ll eat their veggies without complaining, make sure you eat plenty of veggies during pregnancy.
These preferences have also been found in other animals. Rats whose mothers eat a high-fat, high-sugar diet are born preferring the same kind of ‘junk’ foods. Female sheep that eat hay infused with oregano oil give birth to lambs that prefer oregano-flavoured hay over normal hay. Newborn chicks are also influenced by the flavours of their mother’s diet.
What’s it like out there?
There are many amazing examples of unborn animals learning about the world waiting for them on the outside. Quail prefer the sound of whatever call they hear while still inside the egg, even if it is the call of a different species. Superb fairy wrens learn a distinct ‘password’ call from their mothers while still in the egg. After hatching, they mimic this call to get fed by their mothers in the presence of imposter cuckoo birds. Zebra finches use song to communicate information about climate to their unhatched eggs. This, in turn, affects the birth weight of the chicks (it’s better to be small in a hotter climate). There’s little doubt that’s going to come in handy in the face of climate change.
Frog embryos learn to be afraid of salamanders, a common predator, if they are exposed to the smell of danger (a mixture of crushed tadpole and salamander). Tadpoles that are exposed to the smell while still in the egg recognise salamanders as dangerous. Cuttlefish prefer eating crabs over shrimp, but only if they’ve been able to see crabs through the transparent wall of their egg before birth. No wonder animals have evolved such early learning: it’s easy to imagine the benefits of knowing about the world waiting on the outside.
So if you’re pregnant, or you’re near someone who is, be aware: the baby inside is listening to every sound.