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What can babies remember?

In the last article we posted, we talked about why we are unable to remember being a baby. We explained that these kinds of memories are what psychologists call autobiographical memories; they are memories of events that a person has experienced.

But these are not the only kinds of memories we have. We also have what are called semantic memories (memories of facts), procedural memories (memories of how to perform actions) short-term working memory (snippets of temporarily stored information, like when you add up some numbers) and associative memories (like feeling scared of a dog after you were bitten by one). 

Over the last few decades, there have been lots of really interesting studies that show that very young babies, even before they are born, can form memories, despite the fact that they won’t be able to recall them consciously when they are older. 

In her pioneering work, Psychologist Carolyn Rovee-Collier devised an experiment that enabled her to study infants’ ability to remember actions over quite prolonged periods of time. In her experiments, a piece of light string was tied between infants’ ankles and a mobile that was hanging overhead, so that when they kicked their legs the mobile would move. The researchers found that infants as young as 2 to 6 months are quickly able to learn that they can control the mobile by kicking their legs in this way – in other words, they learnt and remembered how to do it. And, interestingly, 2-month-old infants could remember how to make the mobile move the next day and 6-month-old infants could remember it about 2 weeks later. 

Another example of infant memory abilities can be demonstrated using eye-tracking technology – a neat bit of science that lets researchers see exactly where babies are looking.  The researchers showed babies a series of coloured squares that repeatedly disappeared and reappeared. When the squares reappeared, they were either the same colour as before or they were a different colour. The researchers tracked where the babies were looking and for how long, and they found that infants as young as 4 months looked longer at the squares which changed colour – which means they must have remembered what the colour of the square was before. Interestingly, older infants were able to remember up to 4 squares at a time which suggests that their short-term memory abilities increase across the first year of life.

These two experiments demonstrate that babies have very good memory abilities. But can we form memories in the womb? According to Dr Jan Nijhuis (Maastricht University) the answer is YES! By giving gentle “vibroacoustic stimulation” (a very low sound that makes a vibration) to a baby still in the womb, researchers can measure their reactions. Initially, they seem to react quite strongly, almost like surprise or startle. But, after repeating the same stimulation several times, they stop reacting – this is called habituation and is a very basic early form of memory. It’s as if they realise they’ve heard this before and its no longer interesting or surprising. Dr Nijhuis found that it took the babies a lot less time to become habituated to the noise when the experiment was repeated 4 weeks later, suggesting that thy had remembered the stimulus from before – a whole month later. Pretty impressive recall! 

All in all, these experiments show that although we are unable to form lasting memories of our very early life that we’re able to consciously bring to mind as adults, we do form many other kinds of memories right from the word go, and these are almost certainly crucial for helping us navigate the world we encounter as we grow up.

If you’d like to learn more, check out this nice BBC article by our colleague Dr Jane Gilmore from Great Ormond Street Hospital in London.

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