Childhood amnesia
Childhood amnesia, also called infantile amnesia, is the inability of adults to retrieve episodic memories before the age of three to four years. It may also refer to the scarcity or fragmentation of memories recollected from early childhood, particularly those from between the ages of 3 and 6. On average, this fragmented period wanes at around 4.7 years. Around 5–6 years of age in particular is thought to be when autobiographical memory seems to stabilize and be on par with adults. The development of a cognitive self is also thought by some to have an effect on encoding and storing early memories.
Some research has demonstrated that children can remember events from before the age of three, but that these memories may decline as children get older. Psychologists differ in defining the onset of childhood amnesia. Some define it as the age from which a first memory can be retrieved. This is usually the third birthday, but it can range from three to four years in general.
Changes in encoding, storage and retrieval of memories during early childhood are all factors when considering childhood amnesia.
History
Childhood amnesia was first formally reported by psychologist Caroline Miles in her 1895 American Journal of Psychology article "A study of individual psychology". Five years later, Henri and Henri published a survey showing that the average age of the respondents' earliest recollections was three years and one month. 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. In 1910, Sigmund Freud offered one of the most famous and controversial descriptions and explanations of childhood amnesia. Using psychoanalytic theory—but no science-based evidence—he postulated that early life events were repressed due to their inappropriately sexual nature. He asserted that childhood or infantile amnesia was a precursor to the "hysterical amnesia", or repression, presented by his adult patients. Freud asked his patients to recall their earliest memories and found that they had difficulty remembering events from before the age of six to eight. Freud coined the term "infantile" or "childhood amnesia" and discussed this phenomenon in his Three Essays on the Theory of Sexuality. To date, no experimental studies have found any evidence to support Freud's ideas. 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].Methods of recall
The method of memory retrieval can influence what can be recalled. Specifically, different results are obtained when someone is prompted to remember a specific event, given more general guidelines, or asked to recall any memory possible.Cued
Many studies use cued recall to retrieve memories. In its basic form, the experimenter gives the participant a word, and the participant responds with the first memory they think of associated with that word. This method has generally estimated the age of offset at about three to five but can vary. There are several objections to the cue method. One is that memory is recorded per cue word, so it can be difficult to know whether this memory is their earliest memory or the first that came to mind. It may be a problem if participants are not asked to record the earliest memory they can recall that relates to the cue. If the experimenter asks the participant to specifically use childhood memories or the earliest memories associated with a cue, the age estimate can be two to eight years. Even with this measure, cued recall is useful only for bringing to mind memories formed several months after the introduction of that word into the participant's vocabulary. A 2013 study by Bauer and Larkina used cued recall by asking children and adults to state a personal memory related to the word and then state the earliest time that it occurred. The researchers found that the younger children need more prompts or cues. For children and adults, the earliest memory retrieval was around three years old.Free
Free recall refers to the specific paradigm in the psychological study of memory where participants study a list of items on a specific trial and are then prompted to recall the items in any order. In regard to childhood amnesia, free recall is the process by which experimenters ask people for their earliest memories and allow them to respond freely. There is no significant difference when people are instructed to recall their earliest memories with cued recall compared to free recall. 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.Exhaustive
In the exhaustive recall method, participants are asked to record all the memories they can access before a specific age. This method, like free recall, relies on participants to come up with memories without cues. Exhaustive recall yields a better understanding than other methods of the number of memories surviving from early childhood but can be demanding for the subjects, who often have to spend many hours trying to remember events from their childhood. No major differences among word-cued, interview, focused, and exhaustive recall have been found.Accessible and inaccessible memories
The number of early childhood memories a person can recall depends on many factors, including the emotion associated with the event, their age at the time of the remembered event, and the age at the time they are asked to recall an early memory. It is often assumed that not recalling a childhood memory means one has forgotten the event, but there is a difference between availability and accessibility. The availability of a memory is its intactness and existence within memory storage, while its accessibility is dictated by the context in which one attempts to recall it. Therefore, cues may influence which memories are accessible at any given time, even though there may be many more available memories that are not accessed. Other research suggests that people's earliest memories date back to the ages of 3 or 4 years. Usher and Neisser reported that some events, like the birth of a sibling and a planned hospitalization, can be readily remembered if they occurred at age 2. The bits and pieces of such memories that were obtained in their research may not be indicative of genuine episodic memory. 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.According to a study by West and Bauer, earlier memories tend to have less emotional content than later memories, and to be less personally meaningful, unique, or intense. Earlier memories also do not tend to differ greatly in perspective. Certain life events do result in clearer and earlier memories. Adults find it easier to remember personal, rather than public, event memories from early childhood. This means a person would remember getting a dog, but not the appearance of Halley's Comet. Psychologists have debated the age of adults' earliest memories. Most modern data suggests somewhere between the ages 3 and 4 on average. Some research shows that the offset of childhood amnesia is 2 years of age for hospitalization and sibling birth and 3 years of age for death or change in houses. Thus, some memories are available from earlier in childhood than previous research suggested.
Some research suggests that until around the age of 4, children cannot form context-rich memories. More evidence is needed, but the relative lack of episodic memories of early childhood may be linked to maturation of prefrontal cortex. It also suggest adults can access fragment memories from around age 3, whereas event memories are usually recalled from slightly later. This is similar to research showing the difference between personal recollections and known events. Known memories change to more personal recollections at approximately 4 years of age.
Fading memories
Children can form memories at younger ages than adults can recall. While the efficiency of encoding and storage processes allows older children to remember more, younger children also have great memory capacity. Infants can remember the actions of sequences, the objects used to produce them, and the order in which the actions unfold, suggesting that they possess the precursors necessary for autobiographical memory. Children's recall is 50% accurate for events that happened before the age of two whereas adults remember nearly nothing before that age. By age two, children can retrieve memories after several weeks, indicating that these memories could become relatively enduring and could explain why some people have memories from so early. Children also show an ability to nonverbally recall events that occurred before they had the vocabulary to describe them, whereas adults do not. Findings such as these prompted research into when and why people lose these previously accessible memories.Some suggest that as children age, they lose the ability to recall preverbal memories. One explanation for this is that a person develops linguistic skills, memories that were not encoded verbally are lost. This theory also explains why many early memories are fragmented: the nonverbal components were lost. Contrary findings indicate that elementary-aged children remember more accurate details about events than they had reported at a younger age and that 6- to 9-year-old children tend to have verbally accessible memories from very early childhood. Research on animal models seems to indicate that childhood amnesia is not only due to the development of language or any other human faculty.
This increased ability for children to remember their early years does not start to fade until children reach double digits. By age 11, children exhibit young-adult levels of childhood amnesia. These findings may indicate that some aspect of the adolescent brain, or the neurobiological processes of adolescence, prompts the development of childhood amnesia.