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If you ask most people about their earliest , you will typically hear about some memorable event that took place around the age three or four. Often known as infantile or childhood amnesia, our inability to recall events taking place during our very earliest years of life seems universal.

While some children may recall events as far back as their first year of life, these memories tend to degrade rapidly and, as people grow older, that twilight period during which early memories can't be retrieved seems to expand as well. Many older adults may find themselves unable to recall events that occurred before they were 10, possibly due to changes in memory storage over time. Different theories have been proposed to explain infantile amnesia, including the role that language plays in memory consolidation, something that is more difficult for children during the prelingual stage of life.

Researchers have proposed that the infantile amnesia period (IAP) is especially important for development. experiences during this period can cause a cascade of changes, similar to what trauma victims experience. For developing children, this can mean early development of responses more commonly seen in adults. Though this can provide a short-term advantage for children growing up in adverse environments, it can also lead to long-term mental-health issues, including being more vulnerable to disorders—and .

For this reason, dream recall from the very earliest years of life, well within the infantile amnesia period, may play an important role in frequent nightmares experienced by adults, and possibly mental health problems as well.

Tore Nielsen of the Université de Montréal and Dream and Nightmare Laboratory, Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Coeur de Montréal has proposed a -acceleration hypothesis of nightmares which he is using as the basis for his work on early dream recall and nightmare formation. According to this hypothesis, traumatic experiences during the earliest years of life can shorten the infantile amnesia period and influence the kind of nightmares that may be experienced much later. As one example of this, a 2011 study of 5,020 Hungarian adults found that people who were separated from their mothers for at least a month in the earliest year of life were much more likely to have nightmares as adults than control subjects. Other studies have linked adult nightmares to early adverse experiences during preschool years.

In a new research article published in the journal Dreaming, Nielsen provides a comprehensive test of the stress-acceleration hypothesis using over 27,000 participants recruited through his Laboratory website. The "virtual lab" study involved collection of basic demographic data as well as completing the Typical Dream Questionnaire. This 57-item checklist includes familiar dream topics such as being pursued, falling, sexual experiences, flying, and being a child again, which participants could endorse as having experienced in dreams at some point in their lives. Participants were also asked to report which themes occurred most frequently, the age of their earliest nightmare, and how often they had nightmares in the course of a given month.

Of the more than 25,000 participants who completed the study, most recalled dreams from age four or later with age five being the most common age from which they could recall dreams. A notable minority (4.63 percent of participants) recalled dreams from the IAP (1,108 in all) with some reporting dreams as far back as age one. Among the most common themes were dreams of being chased, dreams of falling, dreams of flying through the air, or dreams of meeting some evil force or demon. About 40 percent of all reported dreams contained one or more of these themes.

Results also showed significant support for the stress acceleration hypothesis, with participants recalling dreams from their IAP being more likely to experience nightmares as adults. Even dreams with positive themes, such as eating delicious foods or flying, seemed to be linked to later nightmares, suggesting that any disruption of the normal IAP process could lead to later problems. This is consistent with earlier research showing that adults who are prone to nightmares have unusually good recall of events from their early childhood, whether or not the events were positive or negative. No real difference was found, with males and females both showing this pattern.

Though Nielsen admits that the retrospective nature of this study limits its validity, there are some intriguing findings that correspond to previous research. For example, the 4.63 percent of participants reporting dreams from the IAP matches the estimated 5 percent of all adults in the general population who report a nightmare problem. Also, since we often postdate our earliest memories as we grow older, the actual prevalence of IAP memories may be even higher than this study suggests.

In explaining why a foreshortened IAP might lead to later nightmares, Nielsen suggests that early trauma may influence brain development, especially of the hippocampus, amygdala, and medial frontal cortex—all regions implicated in emotional reactivity and nightmare production. Also, the four dream themes that seem to be most common all seem to be related to early infantile experiences, much as originally suggested. Along with dreams of falling and flying, dreams or being chased or confronting monsters can also relate to the stranger anxiety and nocturnal terrors often seen in small children.

While more research is definitely needed, these results raise some intriguing speculations about early childhood memories and how they can affect us even as adults. They also suggest that early experiences such as lengthy maternal separation or emotional neglect may be far more critical that most of us think.

What is the earliest dream that you can recall? And how might your childhood influence you today?