Think back to your earliest memory. Perhaps images of a birthday party or scenes from a family vacation come to mind. Now think about your age when that event occurred. Chances are that earliest recollection extends no further back than your third birthday. In fact, you can probably come up with only a handful of memories from between the ages of 3 and 7, although family photo albums or other cues may trigger more.
Psychologists refer to this inability of most adults to remember events from early life, including their birth, as childhood amnesia. Sigmund Freud first coined the term infantile amnesia, now more broadly referred to as childhood amnesia, as early as 1899 to explain his adult patients' scarcity of childhood memories [source: Rapaport]. Freud proposed that people use it as a means of repressing traumatic, and often sexual, urgings during that time. To block those unconscious drives of the id, Freud claimed that humans create screen memories, or revised versions of events, to protect the conscious ego.
More than a century later, researchers have yet to pin down a precise explanation for why childhood amnesia occurs. Only in the last 20 years have people investigated children's, rather than adults', memory capabilities in search of the answer. This research has brought with it a new batch of questions about the nuances of young children's memory.
For a long time, the rationale behind childhood amnesia rested on the assumption that the memory-making parts of babies' brains were undeveloped. Then, around age 3, children's memory capabilities rapidly accelerate to adult levels.
However, psychologists have discovered that children as young as 3 months old and 6 months old can form long-term memories. The difference comes in which memories stick around. For instance, it appears that babies are born with more intact implicit, or unconscious, memories. At the same time the explicit, or episodic, memory that records specific events does not carry information over that three-year gap, explaining why people do not remember their births.
But why does this happen, and what changes take place in those first years? And if we can form memories as babies, why don't we retain them into adulthood? On the next page, we'll take a closer look at a baby's brain to find out the answer.
Memory Encoding in Children
To form memories, humans must create synapses, or connections between brain cells, that encode sensory information from an event into our memory. From there, our brains organize that information into categories and link it to other similar data, which is called consolidation. In order for that memory to last, we must periodically retrieve these memories and retrace those initial synapses, reinforcing those connections.
Studies have largely refuted the long-held thinking that babies cannot encode information that forms the foundation of memories. For instance, in one experiment involving 2- and 3-month-old infants, the babies' legs were attached by a ribbon to a mobile [source: Hayne]. By kicking their legs, the babies learned that the motion caused the mobile to move. Later, placed under the same mobile without the ribbon, the infants remembered to kick their legs. When the same experiment was performed with 6-month-olds, they picked up the kicking relationship much more quickly, indicating that their encoding ability must accelerate gradually with time, instead of in one significant burst around 3 years old.
This memory encoding could relate to a baby's development of the prefrontal cortex at the forehead. This area, which is active during the encoding and retrieval of explicit memories, is not fully functional at birth [source: Newcombe et al]. However, by 24 months, the number of synapses in the prefrontal cortex has reached adult levels [source: Bauer].
Also, the size of the hippocampus at the base of the brain steadily grows until your second or third year [source: Bauer]. This is important because the hippocampus determines what sensory information to transfer into long-term storage.
But what about implicit memory? Housed in the cerebellum, implicit memory is essential for newborns, allowing them to associate feelings of warmth and safety with the sound of their mother's voice and instinctively knowing how to feed. Confirming this early presence, studies have revealed few developmental changes in implicit memory as we age [source: Newcombe et al]. Even in many adult amnesia cases, implicit skills such as riding a bicycle or playing a piano often survive the brain trauma.
Now we know that babies have a strong implicit memory and can encode explicit ones as well, which indicates that childhood amnesia may stem from faulty explicit memory retrieval. Unless we're thinking specifically about a past event, it takes some sort of cue to prompt an explicit memory in all age groups [source: Bauer]. Up next, find out what those cues are.
Language and Sense of Self in Memory-Making
Our earliest memories may remain blocked from our consciousness because we had no language skills at that time. A 2004 study traced the verbal development in 27- and 39-month old boys and girls as a measure of how well they could recall a past event. The researchers found that if the children didn't know the words to describe the event when it happened, they couldn't describe it later after learning the appropriate words [source: Simcock and Hayne].
Verbalizing our personal memories of events contributes to our autobiographical memories. These types of memories help to define our sense of self and relationship to people around us. Closely linked to this is the ability to recognize yourself. Some researchers have proposed that children do not develop self-recognition skills and a personal identity until 16 or 24 months [source: Fivush and Nelson].
In addition, we develop knowledge of our personal past when we begin to organize memories into a context. Many preschool-age children can explain the different parts of an event in sequential order, such as what happened when they went to a circus. But it isn't until their fifth year that they can understand the ideas of time and the past and are able to place that trip to the circus on a mental time line [source: Fivush and Nelson].
Parents play a pivotal role in developing children's autobiographical memory as well. Research has shown that the way parents verbally recall memories with their small children correlates to those children's narrative style for retelling memories later in life. In other words, children whose parents tell them about past events, such as birthday parties or trips to the zoo, in detail will be more likely to vividly describe their own memories [source: Urshwa]. Interestingly, autobiographical memory also has a cultural component, with Westerners' personal memories focusing more on themselves and Easterners remembering themselves more in group contexts [source: Urshwa].
More detailed explanations exist regarding childhood amnesia. But brain structure, language and sense of self are its foundation. To learn more about amnesia and memory, don't forget to read the links on the next page.
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More Great Links
- Adams, Jane Meredith. "What it feels like to be a baby." Parenting. November 2007. (April 21, 2008)
- Bauer, Patricia J. "Remembering the Times of Our Lives." Routledge. 2006. (April 21, 2008)http://books.google.com/books?id=BsJ9Qoq74dcC
- Fivush, Robyn and Nelson, Katherine. "Culture and Language in the Emergence of Autobiographical Memory." Psychological Science. 2004. (April 21, 2008)
- Geraerts, Elke; Schooler, Jonathan W.; Merckelbach, Harald; Jelicic, Marko; Hauer, Beatrijs J.A.; Ambadar, Zara. "The Reality of Recovered Memories: Corroborating Continuous and Discontinuous Memories of Childhood Sexual Abuse." Psychological Science. July 2007. (April 21, 2008)http://www.ingentaconnect.com/content/bpl/psci/2007/00000018/00000007/art00002
- Goswami, Usha. "Blackwell Handbook of Cognitive Development." Blackwell Publishing. 2002. (April 21, 2008)http://books.google.com/books?id=0bNZJURnV-QC
- Hayne, Harlene. "Infant Memory Development: Implications for childhood amnesia." Elsevier. 2003. (April 21, 2008)http://www.ballarat.edu.au/ard/bssh/school/nr521/childhood%20amnesia2.pdf
- Janov, Arthur. "Primal Healing: Access the Incredible Power of Feelings to Improve Your Health." Career Press. 2006. (April 21, 2008)http://books.google.com/books?id=nHmknPNeIeoC
- Newcombe, Nora S; Drummey, Anna Bullock; Fox, Nathan A.; Lie, Eunhui; Ottinger-Alberts, Wendy. "Remembering Early Childhood: How Much, How, and Why (or Why Not)." Current Directions in Psychological Science. 2000. (April 21, 2008)http://www.education.umd.edu/EDHD/faculty/Fox/publications/04.pdf
- Peterson, Karen S. "Can Trauma Hide in Back of the Mind?" USA Today. Sept. 12, 2002. (April 21, 2008)
- Simcock, Gabrielle and Hayne, Harlene. "Breaking the Barrier? Children Fail to Translate Their Preverbal Memories Into Language." Psychological Science. 2002. (April 21, 2008)
- Solms, Mark. "Freud Returns." Scientific American Mind. 2006. (April 21, 2008)