Memory is the brain’s ability to encode, store, and later retrieve information and experiences. Determining when we begin forming memories depends entirely on the type of memory involved. While the conscious recollection of personal events appears later in childhood, the brain begins its fundamental work of learning and retention much earlier. This timeline requires distinguishing between the different memory systems the brain uses, which mature at different rates.
The Earliest Beginnings: Prenatal and Newborn Learning
The process of memory formation begins long before birth, operating through automatic and non-conscious mechanisms. Fetal learning is demonstrated by newborns showing a preference for their mother’s voice over a stranger’s voice immediately after birth, suggesting an auditory memory developed during the third trimester. The fetus is also capable of learning patterns in external stimuli, such as a specific story or rhyme read aloud repeatedly during pregnancy.
This earliest retention is demonstrated through simple mechanisms like habituation, where a baby stops responding to a repeated stimulus they have learned to recognize. Newborns also exhibit simple classical conditioning, learning to associate two stimuli, which involves primitive survival-based learning. These initial memories are primitive and non-conscious, setting the stage for more complex development by establishing basic neural pathways for processing sensory information.
Defining Implicit and Explicit Memory
Long-term memory is divided into two main categories. Implicit memory is unconscious and automatic, encompassing skills, habits, and emotional associations, often referred to as procedural memory. This system allows us to perform tasks like riding a bicycle or typing without conscious thought, and it primarily involves brain structures such as the basal ganglia and the cerebellum.
Explicit memory, by contrast, is the conscious, intentional recollection of information and experiences. This category is divided into semantic memory (facts and general knowledge) and episodic memory (specific personal events). The formation and retrieval of explicit memories rely heavily on the hippocampus, a temporal lobe structure that acts as an index for experiences, along with the neocortex.
The Onset of Autobiographical Recall
The ability to form autobiographical memory—the conscious, narrative-based recollection of personal events—marks a significant shift in memory development. This capacity generally emerges between the ages of two and four years. Before this stage, children may recall specific events, but they lack the ability to place them into a continuous, subjective life story.
The development of this conscious memory system is directly tied to the maturation of specific brain regions, particularly the hippocampus and the prefrontal cortex. The prefrontal cortex, which governs organization and context, is necessary for structuring the details of an event into a coherent narrative. Simultaneously, the acquisition of language skills provides the framework for encoding, storing, and later retrieving these complex event memories.
Why We Forget Our Earliest Years
Despite the early learning that occurs, adults rarely retain conscious memories from before the ages of three or four, a phenomenon known as infantile amnesia. This forgetting is explained by two complementary theories: one neurological and one cognitive. The neural theory focuses on the high rate of neurogenesis, or the birth of new neurons, occurring in the hippocampus during infancy and early childhood.
This rapid addition of new neurons and the subsequent formation of new synaptic connections can disrupt or overwrite the existing memory traces that were formed in the same region. The cognitive theory suggests that the lack of a developed self-concept and the absence of sophisticated language skills prevent the proper encoding and organization of event memories in the first place. Memories not verbally encoded or tied to a sense of self are difficult to retrieve later, though non-conscious implicit memories from that time may persist.