Elizabeth Johnston, Investigating Minds, 9/26/97

Lecture 6: Infantile Amnesia

What is infantile amnesia?

Infantile amnesia refers to the general inability of people to remember specific events from the early years of their lives. On the basis of both free recall studies (What is your earliest memory?) and studies for memories of notable and datable early events (the birth of a sibling, hospitalization) psychologists have concluded that there are very few memories from before the age 3 years. The average age of the earliest memory reported is 31/2, with a small but consistent gender difference indicating that females reported earlier memories. If people are asked to recall episodes from the entire life span the number reported before age 8 falls off sharply in comparison to other periods. This indicates that it is not the age of the memories per se that accounts for their relative paucity, rather it is the life period that they occur within (the earliest years) that is sparsely represented in long term autobiographical memory.

Is it due to repression of distasteful memories?

Sigmund Freud was one of the first psychologists to identify the phenomenon of infantile amnesia:
"What I have in mind is the peculiar amnesia which, in the case of most people, though by no means all, hides the earliest beginnings of their childhood up to their sixth or eight year."
His notion was that early childhood memories, particularly sexual ones, were too frightening and distasteful to the child to be preserved as such. Instead these emotional early memories required filtering from conscious awareness, and so took the form of more innocuous and seemingly inconsequential "screen memories". A major difficulty that arises in considering Freud's account as a complete analysis of the phenomenon is that not all reported early memories are emotionally neutral or concerned with trivialities. Memories of troubling experiences from early childhood appear to be no less common than negative memories from adulthood. Freud's model may be restricted to certain client populations.

Is it due to neurological immaturity?

Another natural question to raise is could the lack of early memories be caused by the infant's lack of the neurological equipment necessary for memory formation and storage. In the newborn, the hippocampus and the frontal lobe are immature. The period from 8 to 24 months is a period of intense synaptogenesis in frontal cortex. PET studies during this period of time show vastly increased neurological function in the frontal cortex. After 2 years the processes of myelination and increases in synaptic efficiency continue at a slower pace. There is no abrupt neurological change that either renders information more memorable or that obliterates previously laid down memory traces. In other words, there is no neurological watershed corresponding to the offset of infantile amnesia.

Is it due to a lack of memory abilities per se?

Clever Babies: A number of recent studies have demonstrated that memory is more sophisticated in infancy than previously thought. DeCasper and colleagues demonstrated that newborn infants recognized auditory stimuli presented in the last trimester of pregnancy. Meltzoff and his colleagues used the deferred imitation paradigm to demonstrate sophisticated memory abiltities in children as young as 9 months. Children of 9, 14 and 24 months watched an adult move a toy in a specific, unique manner for 20 seconds. 24 hours later the toy was re-presented and all 3 age groups responded by repeating the adult's action. It is not appropriate to label this ability simply motor or procedural for two reasons: the infants did not experience the extended period of practice that is characteristic of learning motor skills, and because the exposure was so much briefer than any habit based memory would allow. Meltzoff demonstrated that even young infants are capable of storing abstract representations of action sequences in long term memory, not simply learned motor responses. Rovee Collier and colleagues used the mobile conjugate reinforcement paradigm to demonstrate memory in infants as young as 3 months. The infant's ankle was connected via a ribbon to an overhead mobile with the goal of having the infant learn the contingency between his or her kicking and movement in the mobile. In some of the experiments, an additional reactivation treatment is administered prior to tests of retention. Here, following an interval in which some forgetting has occurred, infants get a simple reminder of the set-up (e.g., the mobile, the room, the mobile moving) and are then tested at some later point (at least 24 hours after the reminder). Older infants (6 month olds) require more specific cues for retrieval than younger infants (3 month olds). Once reactivated a memory trace can be retained for at least as long as when it was originally encoded. If the infant's environment provides frequent opportunities for reactivation then theoretically "an individual's early experiences could be remembered over a lifetime". As a consequence of these studies Rovee-Collier et al stressed the importance of reactivation. As Howe & Courage (1993) express it:
Contrary to traditional views of forgetting in which traces are either present but inaccessible (retrieval failure) or simply absent from memory (storage failure in extremis), the memory modifications brought about by reactivation emphasize the dynamic properties of memory.
This is consistent with the view of adult memory drawn by Scachter, particularly his point that "memory is an emergent property of the cue and the engram" (p. 71). In other words, remembering changes what is "stored".

Fivush, Nelson and colleagues have documented children as young as 2 years old can recall personally experiences that occured up to 6 months earlier. For example, Fivush's interviewed her daughter, Rachel, when she was 2 and found that she could remember many things that she had done months before. But by the time she was 8, all Rachel could remember from her first couple of years was a trip to Disneyland (reported in Goleman, 1993). This finding illustrates that the mechanisms for the laying down of long term memories do exist in children as young as 2, so the seeming paradox is why are these memories not retained into adulthood?

Is it due to a lack of ability to tell stories?

Pillemer & White (1989) propose that infantile amnesia is overcome through the linguistic sharing of memories with others. They view memory as composed of two functionally independent systems:
Dual Memory System
Nonverbal, Image-based System Socially Accessible System
  • primitive
  • present from birth
  • addressable by situational or affective cues
  • contains fragmentary information
  • memories expressed through images, behaviors, or emotions
  • learned routines
  • generalized past experiences not linked to specific events
  • accessed through reinstatement
  • emerges slowly throughout the preschool years
  • addressable through intentional retrieval efforts
  • personally experienced events
  • encoded in narrative form
  • actively thought about or processed
  • can be accessed and recounted in response to social demands
  • contains information specific to time and places
  • develops with the acquisition of language
Various pieces of empirical evidence support the idea of a later onset of narrative memory. In a study of vivid ("flashbulb") memories Winograd & Killinger (1983) found that the number of informational categories of narrative (who, where, when, what,...) increased with age: those under 5 produced only 2 or 3, whereas those 6 or older produced 4 or 5. Eisenberg studied two girls between the ages of 2 and 3 and found that the percentage of conversations in which they discussed unique rather than routine aspects of past events increased sharply over the year. Simultaneously, the percentage of memories that were elicited by an adult's question decreased. Tessler (1986) studied 3 year olds and their mothers on a visit to a natural history museum. She found that none of the children remembered any of the objects that they viewed in the museum if they had not talked about them with their mothers. Mother's talk alone was not facilitative, nor was a child's mention alone effective in leading to subsequent remembering. Creating a narrative together cemented particular objects in memory.

Pillemer & White endorse a dialectical or Vygotskian model rather than one of simple cultural transmission or socialization. Through sharing memories with others language becomes available as a means of reinstating memory. After overt recounting becomes established, covert recounting to oneself may take place, and take on the function of reinstatement. Language has a dual function: communication and mental representation.

Is it due to a lack of sense of self?

This is Howe & Courage's (1993) theory: they see the developmental changes in sense of self over the first 21/2 years of life as pivotal in the development of autobiographical memory. Upon reviewing a large body of literature, their conclusion is that before the age of 2-3 years children lack the concept of self necessary to build enduring personal memories.

The development of a sense of self is chronicalled mainly through visual recognition, or mirror tests. By about 3 months of age infants are extremely attentive and positive toward mirrors; as a consequence much early "play" consists of hilarious games involving approaching and retreating from the faces in the mirror. By 9 months infants show awareness of the meaning of the mirror image through their use of the tandem movement of the image and themselves for deliberate play and imitation. Further, their knowledge of the reflective property of mirrors is demonstrated by their turning to see someone who approaches in the mirror. At the age of aprroximately 18 months (although this can vary widely) full visual self recognition is demonstrated in the rouge test: the infant will try to wipe a red blob off her own nose rather than reach out for the mirror. By about 22 months infants can correctly label their image.

Linguistic markers also evidence the growing sense of self. The personal pronouns I and me are acquired first at approximately 22 months, "you" follows about 2 months later. Normal 2 year olds rarely mix up I/me with you. At about 2 toddlers begin to use grammatical morphemes that indicate tense. The first to appear is "-ing" to refer to onging events, followed by the introduction of the past tense.

While Howe and Courage make much of the difference between their "self" hypothesis and Pillemer & White's "socially accessible memory system" hypothesis, they can be viewed as two sides of the same coin. The concept of self and the linguistic ability necessary to share narrative memories are related developments.

Is it due to the lack of a theory of mind?

Between 3 and 4 years of age there is a dramatic watershed in the child's ability to take another's perspective. 3 year olds find it difficult to attribute mental states to others that differ from their own present state of mind. The critical experimental paradigm used to demonstrate this phenomenon is the false belief task. If a child is shown a box of candy (the British Smarties) which contains pencils and is asked what they think it contains they naturally reply "Smarties". They are then shown that they were tricked and its true contents are revealed and asked what they think their friend who is waiting to play the game will think. If the child is less than 4 he or she will ususally respond that their friend will think that the box contains pencils. They are unable to attribute a false belief that differs from their own knowledge to another. The ability to create another person's perspective and to explain the motivations of others is a key aspect of story telling, so this account dovetails well with Pillemer's "socially accessible memory system" hypothesis.

Why is there a discrepancy between the average age of the earliest memory recalled by adults and the age at which toddlers begin to communicate their memories to others?

At least two factors contribute to this:
  1. The lack of accessibility of early memories out of any specific recall context. In other words the difficulty of voluntary free recall.
  2. Difficulties dating early memories.

Sources