[15] In 1904 G. Stanley Hall noted the phenomenon in his book, Adolescence: Its Psychology and Its Relations to Physiology, Anthropology, Sociology, Sex, Crime, Religion and Education.
Using psychoanalytic theory - but without any science-based evidence of any kind - he postulated that early life events were repressed due to their inappropriately sexual nature.
In 1972, Campbell and Spear published a seminal review about childhood amnesia in Psychological Sciences recapping the research conducted to understand this topic from neurological and behavioral perspectives in both human and animal models.
[15][20][21] Even with this measure, cued recall is only useful for bringing to mind memories formed several months after the introduction of that word into the participant's vocabulary.
Free recall, in regard to childhood amnesia, is the process by which experimenters ask individuals for their earliest memories, and allow the participant to respond freely.
It is thought that a major benefit of free recall is that every question gets answered which may, in turn, elicit memories from an earlier age.
An alternative hypothesis is that these apparent memories are the result of educated guesses, general knowledge of what must have been, or external information acquired after the age of 2.
[34] Research on animal models seems to indicate that childhood amnesia is not only due to the development of language or any other human proper faculty.
[35] The importance of animal model research should not be understated as these studies have informed neurobiological findings about childhood amnesia and would be impossible to ethically conduct in humans.
Because infantile amnesia has been observed in animals, the occurrence cannot be explained just by cognition specific to humans such as reading and writing or an understanding of self.
A similar study was done on infants, showing that a behavior that was typically forgotten in a few days could be remembered if the subject was exposed to the reinforcer before a test.
Importantly, the individual differences described below tell us that elaborative parenting styles and emphasis of cultural history when teaching children may result in recollection of earlier childhood memories.
It has been suggested that since sons are prized far over daughters in China, parents may have more elaborate, evaluative, and emotional reminiscent styles with boys than with girls.
[42] Black women also tend to report a low proportion of personal experience[42] which is independently correlated[clarify] with being older at the age of first memory.
[40] Additionally, studies on the Black American population, which is considered a more collectivist society, have not indicated later first memories than non-collectivist cultures.
This concern has led the APA to advise caution in accepting memories of physically and sexually abusive events from before the age of two.
[52] Freudian theory, including his explanation for childhood amnesia, has been criticized for extensive use of anecdotal evidence rather than scientific research, and his observations that allow for multiple interpretations.
In addition, they demonstrate considerable problems with visual, pictorial, and facial memory storage and retrieval compared to non-traumatized individuals.
[9] This implies that trauma can disrupt the formation of early childhood memories, but does not necessarily give evidence for Freud's theory of repression.
The evolutionary psychology states that if a past event was particularly frightening or upsetting, one is apt to avoid a similar situation in the future, especially if it is endangering to one's well-being.
[2] Various findings have shown that events such as hospitalization and the birth of a sibling are correlated with an earlier offset of childhood amnesia, which may be because they were more emotionally memorable.
[20] Other seemingly emotional memories such as the death of a family member or having to move do not affect offset, possibly because the events were not as meaningful to the child.
[20] One possible explanation for childhood amnesia is the lack of neurological development of the infant brain, preventing the creation of long term or autobiographical memories.
[2] The development of the Medial Temporal Lobe (MTL), which contains the hippocampus, has been found to specifically have a defining impact on the ability to encode and maintain memories from early childhood.
[31] This discovery that three-year-olds can retrieve memories from earlier in their life implies that all necessary neurological structures are in place to recall episodic information over the short-term, but evidently not over the long-term into adulthood.
[58] The finding that all altricial species experience profound forgetting of episodic information formed during infancy suggests that human-centric explanations of infantile amnesia are inherently incomplete.
This retrieval lasted for up to three months, suggesting the infantile amnesia was underlaid by a biological failure to access, rather than encode, said memories.
[2] As toddlers grow, a developing sense of the self begins to emerge as they realize that they are a person with unique and defining characteristics and have individual thoughts and feelings separate from others.
[2] The developmental explanation asserts that young children have a good concept of semantic information but lack the retrieval processes necessary to link past and present episodic events to create an autobiographical self.
[2] Through elaboration and repetition of events experienced, adults help children to encode memories as a part of their personal past and it becomes essential to their being.