"The-Cat-In-The-Hat" studies and other work by Tony DeCasper

Eve Whitwell

Research Assistant

It is perhaps now common knowledge that babies are born with with the ability to recognise their mother’s voice, however, in the early 1980s this was not the case. Thanks to Tony DeCasper, who sadly passed away in July this year aged 75, we now have a much greater understanding of what babies learn before they are even born. Throughout his scientific career he performed groundbreaking research into prenatal experiences and how they affect future development. His research found that not only do newborn infants prefer the sound of their mother’s voice to other female voices, they will also actively work to produce the sound of their mother’s voice over another voice. He also performed the famous “The-Cat-in-the-Hat” studies, which provided the first direct evidence that infants form memories before they are even born.

Research on newborn infants is much more difficult than testing older infants and adults. In studies with older babies, we can find out what they have learned and which stimulus they prefer by measuring where they look or which object they reach for. Such techniques, however, cannot be used with newborn infants because they do not have the necessary motor skills. DeCasper’s early research focused on learning in animal models and when he decided to change his research participants from pigeons to newborns, he had to come up with a novel way to measure what babies’ might have learned before they were born. His technique, called high amplitude sucking, capitalises on a reflex that babies are all born with, that is to suck things that are put into their mouth. In high amplitude sucking studies, babies are given a dummy that is connected to a pressure monitor. The researchers play different sounds to the baby through special headphones and measure how fast they sucking on the dummy.

In his original research on newborn infants, babies younger than 3 days old learned how they could “choose” between two different recordings by changing how quickly they sucked on the dummy. One of the recordings was their mother’s voice, while the other was the voice of an unfamiliar woman. Amazingly, the babies chose to hear their own mother’s voice over another female voice, indicating they prefer listening to the familiar sound of their mum.

These results suggested that infants learn about the sound of their mum’s voice in the womb and recognise it after they are born, but do they simply remember what she sounds like, or perhaps are they listening and learning about what she says too? To test this idea, DeCasper designed the now famous“The-Cat-in-the-Hat” studies. In these studies, mums were asked to read Dr. Seuss’s book “The Cat-in-the-Hat” to their baby in the 6 weeks prior to birth. When tested using the high amplitude sucking procedure shortly after birth, babies preferred to listen  to “The-Cat-in-the-Hat” over a different book that they had not heard before, even when it was read to them by a stranger. This extraordinary research provided the first direct experimental evidence that babies in the womb are learning about not only just the characteristics of their mother’s voice, but the content too.  

Next time you call out to tell your child it’s time to go home don’t forget they learnt to recognise the sound of your voice before they were born, and we only know this thanks to the amazing work by Tony DeCasper.