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Infantile amnesia

We all experience a phenomenon called infantile amnesia: a gap in our memory for the personal events happening in the first few years of our lives.

Infantile amnesia

What do babies remember?

We all experience a phenomenon called infantile amnesia: a gap in our memory for the personal events happening in the first few years of our lives. Usually what we know of these years is due only to what we’ve heard from our parents (or others) and seen in photos. Toddlers are perfectly capable of remembering things at this time; they recognize and remember people, learn words and remember places and experiences. However, access to these episodic memories (memory for personal events) seems to disappear as children grow older, only to be replaced by more permanent adult memories. We know that this episodic memory is different from procedural or factual memory, such as how to walk or talk, which remains.

Psychologists have long wondered what is responsible for the loss and why perfectly good memories disappear unless they are constantly being refreshed. One early suggestion is that because many of these memories are created before language skills become solidly established, early memories become hard to retrieve later when much of our mental processing is language dependent. Others have suggested, using a theory of mind, that to maintain episodic memories one needs to have a developed sense of self, which only becomes established later in development. More neurologically based theories have suggested an inability of the immature brain to form long-lasting episodic memory circuits.

Memory problems are often divided into three types: problems with encoding memories, difficulties in maintaining the memory and problems with memory retrieval. Many of us know about retrieval problems when we need to introduce an old friend and her name is suddenly lost to us. Her name has been learned, we have used it in conversation many times, but now we “draw a blank.”

Neuron pruning
It has not been clear with infantile amnesia if the problem is with establishing, maintaining or retrieving the memory. A recent study by Travaglia and associates in the journal Nature Neuroscience suggests that the reason for this amnesia is that the hippocampus (an essential part of the brain involved in memory) undergoes a neural reorganization at a critical period in early childhood. Their study discovered that baby rats also show infantile amnesia. Specifically, if 17-day-old rats are presented with an object followed by a shock, the young rats quickly learn to avoid the object. By day 24 the memory is gone, but if the animals receive a reminder shock, without the object being present, they now exhibit again an avoidance of the object. They still remember the earlier pairing but need to have it brought back. Similar “recovery of memories” can be shown in young children. Travaglia’s study suggests that infantile amnesia is a problem of memory retrieval, not maintenance. It also implies that neither language nor a sense of self is critical for effective memory.

The authors then manipulated the molecular and pharmacology of the rat’s hippocampus in this period. They found that reorganization of this neural area occurs quickly during a critical period and that this rewiring can be manipulated (slowed down or deferred) by molecular and pharmacological interventions. Humans also have critical periods in brain development that have profound effects on our behaviour. As very young babies our brains prune neurons and their connections, keeping only those we use. One of the later brain changes occurs in late adolescence and is important for reducing the bad impulsive decisions that young adults sometimes exhibit. It is only in our early twenties that the frontal cortex (the part of the brain over our eyes), which is critical in decision making, is fully developed.

As our Lord was completely human, he too must have experienced infantile amnesia in his human nature and had to deal with other changes that happen to all our brains. In his human nature he probably did not remember the Magi, except as Mary told him about their visit. It is not clear what this means for his divine nature. In a famous passage in Philippians (2:7), scripture speaks of Jesus emptying himself, so he in some way accepted the limitation of being human. Thankfully the Father does not suffer amnesia, maintaining his love for us and only voluntarily putting our sins out of his mind.

About the Author
Infantile amnesia

Rudy Eikelboom, Columnist

Rudy Eikelboom, a Professor of Psychology, has now been on the dark side of the University as Chair of the Psychology Department at Wilfrid Laurier University for five years, and his hair is considerably grayer. He is proud of his two children and three grandchildren (soon to be four). A member of the Waterloo Christian Reformed Church, he serves on the Waterloo Campus Committee. Despite all these activities, he still enjoys working with rats when he can find some time.