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The experimental psychologist observing how children’s memories grow

20 June 2024

Interview Development Neuroscience Psychology

Zoe Ngo is connecting brain development to memory growth

Image by Claudia Flandoli for BOLD

Zoe Ngo is an experimental psychology researcher at the Max Planck Institute for Human Development in Berlin. Zoe studies how different components of memory and related brain areas develop with age. She is exploring the building blocks of memory development in the hope of using this information to optimize teaching practices. Annie Brookman-Byrne talks with Zoe about recent technological innovations and the biggest mysteries in memory science.

Annie Brookman-Byrne: What are you trying to discover about the development of memory through your research?

Zoe Ngo: Memory has two functions. It enables us to access the specific events that make up our past, and at the same time it allows us to amass general knowledge that helps us predict possible futures. Both functions are crucial as we go about our everyday lives. In my research, I investigate how children develop these memory skills between the ages of 4 and 8.

With my colleagues, I study children’s memories of specific events from their past, how they may confuse similar experiences, and their general knowledge gained from past experiences. We investigate how these different components develop in relationship to one another, and how brain maturation explains memory growth.

We track how each component of memory changes within the same child over the course of childhood. We also measure changes in the size of certain areas of their brains, and changes in the connections between different areas. We are using this information to determine whether changes in the brain predict children’s later memory abilities. We hope our work will contribute to the development of educational technologies and interventions that take into account children’s individual memory development profiles.

ABB: Why is it important to understand how memory develops?

ZN: Generalization and memory skills are the cognitive backbone of school readiness and success. As children transition from early to middle childhood, most enter formal schooling. This coincides with the time when their memory development appears to be most rapid. Understanding how various memory functions develop during this formative period is crucial for figuring out how we can optimize children’s learning. Promoting positive development of these skills early in life yields long-lasting benefits for the wellbeing and professional outcomes of every child.

Understanding how children acquire and retain certain kinds of information more than others at different ages will help us tailor pedagogical practices to young learners. How can children’s attention be directed to avoid memory confusion? And how can educators cultivate an enriched learning environment for every child? Answering these questions requires understanding the memory profiles of each learner.

ABB: Has memory development research changed over time?

ZN: I have seen two positive changes in the past decade. First, there has been an increase in insights from computational models of the brain informing memory development research. These models help us understand the building blocks of well-functioning memory. They also lead to new predictions about how specific aspects of brain maturation support a set of memory abilities, which we can then test.

Second, recent innovations in neuroimaging techniques have advanced our understanding of the relationships between the brain and memory growth. For example, thanks to advanced neuroimaging techniques we have data on the connections between areas in the developing brain. The connections facilitate communication between different, and sometimes remote, brain regions. We and many others have begun to test how the characteristics of these connections are associated with memory functioning in young children.

We are also better able to distinguish different parts of the brain, including the hippocampus, which is crucial for learning and memory. We have been able to examine whether differences in the size of the hippocampus may help explain differences in memory abilities among children of the same age.

ABB: What are the biggest mysteries in this field?

ZN: In early development, children are not very able to lay down long-lasting memories of individual events. Over the same developmental period, however, they excel at accumulating vast knowledge about their surroundings through repeated experiences. Four-year-olds can quickly grasp what a day at kindergarten entails – learning, for example, that storytime follows lunchtime and precedes naptime. Yet they may find it very challenging to remember the details of activities from the day before, such as who sat next to them to at lunch. We do not yet understand how acquiring this general knowledge can occur in the face of weak memories of specific past events.

Another longstanding mystery is why our early life experiences are lost to recollection later in life. Researchers have discovered some important characteristics of this phenomenon, such as children’s age at the time of a given event and the length of time that has passed, that impact the retrievability of early events.

“In early development, children are not very able to lay down long-lasting memories of individual events.”

For example, in a study in the 1990s children were asked about a salient preschool event such as a fire alarm that had occurred 7 years prior. Some who were 4 years old at the time of the event provided a narrative account of what had happened, whereas none of those who were just 3 years old had any recollection of the event. In a more recent study, children aged around 5 to 7 recalled more of their personal life events from age 3 than children 2 to 3 years older – showing that more events were forgotten as more time passed.

Exciting evidence from research in rodents suggests that memories of early life are stored in the brain and remain there, but are not accessible later on. Moving forward, we need innovative methods to find evidence for early-life memory traces in humans. If such traces do in fact exist, why do we lose access to these memories later in life?

ABB: What are your hopes for the future in this field?

ZN:I would love to see more cross talk between lab-based assessments of memory and real-world memory abilities. Many labs around the world have put tremendous effort into developing well controlled and age-appropriate assessments of children’s memory abilities. Other researchers have devised creative methods to characterize children’s memory abilities in the real world, such as remembering their personal pasts. Unfortunately, there is little communication between these two research traditions. We need to learn more about how our theories explain not only children’s performance on lab-based tasks, but also their memories from everyday life. Drawing direct connections between the two would significantly advance our understanding of memory development.

I also hope to see cross-species comparisons. Animal research has yielded powerful insights into how the brain underpins memory growth using techniques that are not possible in humans. It would be great to understand similarities and differences in memory between humans and rodents or primates. This could help solve the longstanding mystery of why events in infancy and early childhood tend to be inaccessible to us later in life.

“This could help solve the longstanding mystery of why events in infancy and early childhood tend to be inaccessible to us later in life.”

For example, we may be able to use methods that are not possible in humans to detect memory traces formed during an animal’s infancy and even activate them when the animal reaches adulthood, providing clues to what may also be happening in the human brain. Further, we can draw on knowledge of animal brain development on a molecular level to advance our understanding of the processes that underpin children’s memory growth early in life.

Finally, I hope there will be more studies of how memory develops over time within individuals. Over 90% of the research on memory development in childhood has used a cross-sectional design, comparing children of one age with children of a different age. This approach does not tell us about developmental changes within the same child over time, or how changes may differ between children. I hope that future research will look at individual variability in memory competence over time, and how that relates to brain maturation. I would love to see this knowledge used to inform pedagogical practices that are attuned to the memory development of each individual child.