None of us remember being babies. In fact, most adults’ earliest memories come from the age of about four years old – and scientists don’t really know why.
Researchers have long believed this phenomenon – called 'infantile amnesia' – was because very young children didn’t form memories of specific events while the part of the brain that dealt with memory, the hippocampus, was still developing.
But a new study from Yale University has blown that theory out of the water. It found that babies do store these types of memories in their hippocampus, opening up more questions about why we don’t remember them.
“This study shakes up the landscape of potential explanations for infantile amnesia,” senior author of the study, psychologist Professor Nick Turk-Browne, told BBC Science Focus. “This work suggests that actually, infant amnesia may be a problem with accessing memories that have been stored, rather than an inability to store the memories in the first place.”
The team of scientists showed babies, aged four months to two years, a series of images of faces, objects and scenes while scanning their brains.
A few minutes later, they showed the babies an image they had seen before and measured how long they looked at it, as well as their hippocampal activity. They found that the babies seemed to remember the images from earlier
Different types of memory
The experiment investigated a specific type of memory called episodic memory, which is the recall of a single event such as a conversation with a friend or a day out at the beach.
It’s the opposite of statistical memory, which is learning that is formed across many points in time, such as gradually understanding words in a language.
Scientists previously discovered that both types of memory are stored in the hippocampus in adults.
This was mysterious, explained Turk-Browne, because the hippocampus was not believed to be functional until the age of about four or five, but we know that statistical memory is essential to babies as they learn to make sense of the world around them.
“Then we found that the infant hippocampus, as early as three months, engages in statistical learning,” said Turk-Browne. That’s where this study came in, to test whether the same was true of episodic memory.
Scanning the brains of wiggly babies
This type of test had not been done before, largely because it requires magnetic resonance imaging (MRI) scans to see deep into the brain, and these are difficult to perform on babies.
“We spent many years figuring out how to do functional MRI experiments in babies,” said Turk-Browne. “You can’t move at all during an MRI, and babies wiggle. They can’t follow instructions because they don’t understand language, and they have short attention spans.”
But, he said, there was “great satisfaction” in finding the tools to “answer one of these age-old questions about humanity,” and open up more doors to new questions about how babies’ memory works.
Where do your earliest memories go?
The next questions the scientists are trying to answer are, if babies can remember things, where do those memories go and how long do they last?
“I think there’s a real possibility that memories stored during infancy might persist into childhood or adulthood,” said Turk-Browne.
To test this, parents will record home videos of key events from their babies' perspective. Later, researchers will scan the babies' brains as they watch their own videos and compare their reactions to videos of another child’s experiences. This will help reveal how much they remember.
“My guess, based on our findings, is that some infantile amnesia is not the lack of hippocampal memories, but rather our inability to access those memories in the hippocampus,” said Turk-Browne.
He explained that early memories may fade because we lose the right cues as our brains develop. However, cues like smells might help reactivate your lost memories.
“If we could find ways, at least into childhood, to cue the memories in the right way, we might be able to reactivate early hippocampal memories,” said Turk-Browne.
Read more:
- The new science of memory: How to improve yours, and the great myth of photographic memories
- Where do memories form and how do we know?
- Here's how a false memory could be planted in your brain
About our expert:
Professor Nick Turk-Browne is a cognitive psychologist at Yale University and director of Yale's Wu Tsai Institute. Turk-Browne received his Bachelor's degree in 2004 from the University of Toronto in Cognitive Science and Artificial Intelligence and his Doctoral degree in 2009 from Yale University in Cognitive Psychology. He started his lab in 2009 at Princeton University, where he rose from Assistant Professor to Full Professor before returning to Yale in 2017.
