by Lauren Lin

All of us have heard funny stories about things we did when we were toddlers and preschoolers, but why can’t we recall these events ourselves?  Being unable to remember experiences that we had before turning three or four, a phenomenon called infantile amnesia, is probably one of the strangest things to happen to us during development.       

Sigmund Freud, who coined the term infantile amnesia, theorized that people forget the first few years of their lives because they repress inappropriate and traumatic memories from their childhood as a defense mechanism.  This ties into his psychosexual theory of development, which maps out five stages, each focusing on a specific body part linked to our sexual drives.  By progressing through or becoming stuck on certain stages while exploring their sexuality, children slowly form their personalities and behaviour as an adult.  Although recent findings support Freud’s observations of infantile amnesia, his theory for why it happens has been discredited.     

The current model of infantile amnesia includes both the inability to recall any events from around the ages of two to three, as well as having very few memories between the ages of three to seven.  This indicates that infantile amnesia isn’t a sudden switch from when are able to remember everything to when we start to forget our life events.  However, you might wonder that if young children are still able to remember what happens in their lives, like their birthday parties and what they did at school, when do we start forgetting these things?  In a study done by Abbema and Bauer, three-year-old children were told to talk about recent events with their mothers. Then, the children were brought back at ages seven, eight, or nine, to recall the events from when they were three. This study found that the number of nine-year-olds who could recall the same events was significantly lower than the number of seven-year-olds who could recall the events.  Therefore, they concluded that the progression of the amnesia seems to happen quickly between the ages of seven and nine. This rapid amnesia cannot be explained by how people forget memories normally (i.e. as more time passes, the more likely you are to forget something).  In fact, when adults aged 20, 35, and 70 were asked to recall childhood memories, there were no drastic differences between the age groups.       

Another theory behind the cause of infantile amnesia examines the impact of language.  Learning a language, and subsequently encoding our memories in terms of verbal cues, might explain our inability to remember events that happen before we are fully fluent in a language.  Although this theory is supported by research, many believe it to be incomplete, since children are able to form memories before learning languages (suggesting that language is not essential for memory). Non-human animals also display signs of infantile amnesia, and there have been cases in which children were able to recode preverbal memories with verbal cues.  

​For example, in a 2007 study, two-year-olds were shown a remote-controlled bubble machine with six colours of bubble mixture.  Experimenters taught the children that only a specific colour of bubble mixture would work in the machine. The colour was pointed out to the children, without providing a name for it. The children had two days to play with the machine, and the experimenters only turned it on when a certain colour was put in.  In the following weeks, the children were taught colour names, and then were asked to name the colour of mixture that turned on the bubble machine, to point out the colour on a colour chart, and to actually put the colour mixture into the bubble machine to activate it.  They found that more children were able to name the target colour than if it occurred by chance, suggesting that their previous experience with the colour could have helped with learning the colour name.  However, about 75% of the children were unable to name the target colour even though they could point to it, indicating that most children were unable to recode their preverbal memories with verbal cues.  Despite disproving the belief that children cannot recode their memories verbally, this study also provides evidence that there are still many children who aren’t able to re-code their memories.  As language abilities improve, people rely more on language for encoding memories, which may be the reason why most preverbal memories are lost.  The relationship between language development and infantile amnesia is complex and still not completely understood, but it does imply that infantile amnesia stems from a problem with retrieval rather than storage.       

In Carolyn Rovee-Collier’s study on infant memory, she taught infants to kick a ribbon to move a crib mobile. The infants were able to remember how to activate the mobile, showing that they already developed memory systems and mechanisms similar to an adult’s. Rovee-Collier also found that if she modelled how to activate the mobile herself, the younger infants who had forgotten how to do it after a few days or weeks were able to remember how to kick to start the mobile. This suggests that the memory had not been lost. Additionally, if an object on the mobile was switched, infants no longer remembered to kick.  Some researchers hypothesize that we can’t retrieve some memories because contextual prompts have changed, since we grow taller and sometimes have to look downwards on things that used to be much higher than we were.  Rovee-Collier also suggests that “contextual information disappears from memories that have been reactivated once or twice,” and so we might sometimes recall a childhood memory but not register that it is an early memory because we have forgotten where and when it took place.        

In addition to language and changing contextual cues, there seems to be a biological cause for infantile amnesia.  Josselyn and Frankland suggest that infantile amnesia may be caused by continued neurogenesis in the hippocampus, an area of the brain that is heavily associated with memory.  This seems to be supported by the fact that only when the formation of new neurons slows down, we are able to have long-term memories.  They propose that rapid neurogenesis might be disrupting synaptic connections that exist in previously established hippocampal memory circuits, and so those memories aren’t intact anymore.  However, Josselyn and Frankland don’t think that hippocampal neurogenesis is the sole factor in infantile amnesia, especially since the hippocampus is connected with multiple other brain structures involved in memory.       

To conclude, infantile amnesia seems to be caused by an inability to retrieve our memories and is not a result of losing them or having them thrown away into the Memory Dump like in the movie Inside Out.  It would be incredibly interesting if researchers found a way for us to recall our childhood memories, but considering all the embarrassing situations we probably got ourselves into as kids, it might be better to preserve infantile amnesia.