March 20, 2025 – For the first time, scientists have found that babies are able to store memories in the brain region called the hippocampus. The ability appears to start around 1 year old.
What still remains a mystery is why these early memories elude us, unable to be retrieved or recalled. Our earliest childhood memories emerge around 3½ to 4 years old, a phenomenon that has long drawn popular and scientific fascination.
"There's a general science curiosity about why we have this blind spot in our life," said Nick Turk-Browne, PhD, co-author of the study and a Yale University psychology professor. He’s an expert in how the human brain learns and remembers.
"Why it matters scientifically is because it tells us something about how the brain develops and the priority that the brain places on certain kinds of learning and memory," he said. "It's a very open and interesting question of what function do memories for specific events have for babies and toddlers, when previously we didn't think they had them. So that's an unknown – the 'why we have them' question."
That early memory gap was first documented in the late 19th century. Later, Sigmund Freud suggested "infantile amnesia" may serve a protective purpose. Modern research has relied on behavioral indications of whether a baby has formed a memory, and there’s also evidence that baby rodents form memories.
"Because babies can’t talk, these other measures – how they move their body, what they look at, how fast they suck on a pacifier – these are indirect measures for memory," Turk-Browne said. "Ours is the first study to show that the hippocampus in human infants is able to store memories."
The study, published today in the journal Science, included 26 infants ranging in age from 4 to 25 months old. Half were under a year old. The babies were shown three types of images – faces, objects, and scenes. None of the images were things they would have seen before the experiment.
The study relied on a type of brain imaging called functional MRI (fMRI) that measures brain activity through sensitivity to blood flow changes. It’s the same tube-like machine that is traditionally used, with some modifications.
"Babies are not great at MRI," Turk-Browne said. "They can't understand your instructions, so they don't follow them, and they move a lot, and they have short attention spans."
"That's the deep innovation here," he said. "We figured out how to do a memory experiment where the baby was awake in an MRI."
The researchers made a special, comfortable vacuum pillow that the baby is nestled into for the sessions, which last five to 10 minutes. A parent is nearby in the room to help the baby feel comfortable.
"We designed tasks that they find really engaging, with dynamic stimuli that kind of loom at them, so they're attention-grabbing," said Turk-Browne, who is also director of Yale’s Wu Tsai Institute, which focuses on studying neuroscience and cognition (the body processes for thinking and acquiring knowledge).
Starting around the age of 1 year old, the babies’ brains reacted differently to images they had previously been shown as part of the experiment process, compared to new images.
Follow-up research is already underway, including a study where parents record a weekly video of their babies’ lives, and the babies come in for MRI scans every three months and view their own videos and videos from other babies. The goal is to examine long-term memory skills.