Rolf Degen summarizing... The earliest memories of our childhood mostly consist of innocuous, disjointed scraps of experience, often devoid of emotion and without a coherent narrative

Early Childhood Memories Are not Repressed: Either They Were Never Formed or Were Quickly Forgotten. Mark L. Howe. Topics in Cognitive Science, December 2 2022. https://doi.org/10.1111/tops.12636

Abstract: Early childhood events are rarely remembered in adulthood. In fact, memory for these early experiences declines during childhood itself. This holds regardless of whether these memories of autobiographical experiences are traumatic or mundane, everyday experiences. Indeed, what people tend to remember from their childhoods involves relatively innocuous experiences, ones often devoid of emotion. In this article, I provide an overview of the types of memories adults recall from their childhoods and the ages at which these memories are believed to have been formed. Along the way, I provide a brief exegesis of the neurobiological and cognitive underpinnings of early memory development. I will show that changes and growth in neural interconnectivity as well as the development of various cognitive structures (e.g., the inception of the cognitive self) help propel the emergence of a mature autobiographical memory system, one that can and does serve as a reconstructive base for remembering events that occur in later childhood and adulthood. During the course of this review, I detail the nature of early memories, their fragility, and the adaptive consequences of forgetting and supplanting these memories with newer, more age-appropriate experiences throughout childhood.

3 Forgetting as adaptive

The idea that forgetting is an adaptive process has gained considerable currency recently (e.g., see Nørby, 2015; Ryan & Frankland, 2022). A central tenet here is that “… information loss prevents overfitting to perceptual situations that are too specific. In other words, degrading stored information contained in a memory allows organisms to behave more flexibly and promotes better memory-guided decision-making” (Ryan & Frankland, 2022, p. 179). Forgetting then, in childhood and adulthood, is something that occurs in an adaptive memory system, one that is geared to promote the survival of the remembering organism (also see Howe & Otgaar, 2013).

A related mechanism that, although not necessarily leading to the complete erasure of information but simply its modification, is reconsolidation. Like consolidation, reconsolidation involves initial trace volatility of engrams in memory followed by the stabilizing of the engram, in this case, following the retrieval of a previously stored memory trace. During the period of instability, additional information can be added to the original memory trace, information that subsequently becomes part of the newly restored engram. Through this process, the original trace is updated with new information, making that representation more pertinent to functioning in the organisms current environment.

Concerning the forgetting of early childhood experiences, one model suggests that the ongoing maturation of the hippocampal complex may make infantile memories inaccessible to later retrieval attempts (Alberini & Travaglia, 2017). The idea here is that there are critical periods in memory-related neural development in which the young organism is learning to learn and remember. Although memory traces may be laid down early in this development, forgetting of these traces might occur due to the maturation of the hippocampal memory system in response to these infantile experiences, making memories of these early experiences inaccessible to retrieval attempts in this more mature memory system.

Another process that exacerbates forgetting is hippocampal neurogenesis (e.g., see Akers et al., 2014). In infancy as well as adulthood, new neurons are generated in the hippocampus (specifically, the subgranular zone of the dentate gyrus), neurons that integrate into hippocampal circuits permitting new learning. This integration not only aids in the storage of new memories, but can also affect memories that are already stored. That is, as these new neurons integrate into the hippocampus, they establish new synaptic connections that either compliment those that already exist or may even replace those existing ones. Thus, high levels of hippocampal neurogenesis can lead to higher levels of forgetting of information already stored in memory. Because hippocampal neurogenesis rates tend to be high during infancy (see Akers et al., 2014), rates of forgetting should be high then too. The fact that these high rates of neurogenesis are seen across many species during infancy, and these same species evince high rates of infantile amnesia, neurogenesis may be partly responsible for increased forgetting of early life events (Akers et al., 2014; Josselyn & Frankland, 2012; also see Howe, 2011). Importantly, because neurogenesis reconfigures hippocampal circuits, memories originally served by these circuits have been fundamentally altered and cannot be reinstated as they no longer exist in their original form (Akers et al., 2014). As development proceeds, neurogenesis rates decline, making it easier (neurobiologically, at least) to retain hippocampally dependent (declarative/autobiographical) memories over longer and longer periods of retention. Thus, given the need to update early memories in light of new experiences, as well as the prodigious rates of neurogenesis early in life, both of these factors contribute to the increased forgetting, not repression, of early childhood experiences.