The question of when babies develop long-term memory is complicated because memory is not a single function but a collection of evolving abilities. Long before a baby can consciously recall a specific past event, their brain is already storing information and learning from experiences. The ability to form memory is present at birth, but the type of memory a newborn uses differs from the conscious recollection associated with adult memory. Understanding the answer requires distinguishing between unconscious memories and the deliberate recall of personal history, which emerges much later.
Defining the Kinds of Memory Babies Use
Babies are born with implicit memory, which is a form of unconscious, non-declarative long-term memory. This type of memory includes procedural skills, habits, and emotional conditioning. For example, a newborn quickly learns to recognize their parent’s voice and smell, and the comforting feeling associated with these familiar stimuli creates a mental model of expectation.
Implicit memory allows infants to learn motor skills, like the reflex needed for suckling, and later, the complex coordination required for crawling and walking. This learning is automatic and does not require conscious thought or effortful recall. It is controlled by early-developing brain structures like the striatum, cerebellum, and brain stem, which mature quickly.
In contrast, explicit memory is the conscious recall of facts or events. This memory includes episodic memory—specific personal experiences, such as a first birthday party. While implicit memory is robust and present from birth, the system for explicit memory develops much later because it relies on slower-maturing brain regions.
The Timeline for Developing True Long-Term Recall
The timeline for developing explicit memory begins with short-term recognition, which is evident in the first few months of life. Researchers have shown that two-month-olds can remember an event for about five days, and this retention period increases with age. By six months, infants can remember actions for approximately 24 hours, demonstrating a foundational memory capacity.
The mobile-kicking paradigm shows that six-month-old infants can remember a learned action for up to three weeks, and nine-month-olds can retain that memory for a month. This ability to recognize and imitate an action after a delay is evidence of declarative memory developing throughout the first year. However, this ability is recognition-based and context-dependent, meaning a change in the environment can cause the memory to be lost.
Long-term episodic recall—the ability to remember a unique event and place it in personal history—emerges much later. This type of memory generally begins to solidify between 18 and 24 months of age. This period coincides with two other major developmental leaps: the rapid acquisition of language and the formation of a sense of self.
The Brain Structures Supporting Memory Growth
The delayed timeline for conscious memory is directly linked to the slow maturation of brain structures. Explicit memory formation is highly dependent on the hippocampus, a structure deep within the medial temporal lobe that functions as the brain’s “save button” for new experiences. Although its basic formation begins before birth, the hippocampus continues to develop rapidly throughout the first few years of life.
The prefrontal cortex (PFC) is also a structure required for organizing, retrieving, and retaining memories. The PFC is important for working memory and is considered the last major brain region to undergo a rapid burst of development, which starts around 30 months. The immaturity of these two areas restricts a baby’s ability to consolidate and store memories in a stable, easily retrievable form.
As these structures gradually mature, the brain becomes more capable of forming complex neural networks needed for conscious recall. The rapid growth and changes occurring in the hippocampus during the first year mean that even if a memory is formed, the physical storage mechanism is still too plastic to keep it stable. The functional connectivity between the hippocampus and the cortical regions necessary for long-term storage is not fully operational in early infancy.
Why Early Memories Fade (Infantile Amnesia)
Even though explicit memory begins forming around 18 to 24 months, most adults cannot consciously recall events from before the age of three or four; this phenomenon is called infantile amnesia. The inability to retrieve these early memories is not due to a failure to form them, but rather a failure to access them years later.
One primary theory suggests a neurological basis, pointing to the rapid development of the brain during early childhood. The massive creation of new neurons in the hippocampus, known as neurogenesis, may essentially “write over” the existing, unstable memories. The memory traces formed in a young, highly plastic brain may be reorganized to the point of being irretrievable by the adult brain.
The linguistic and cognitive theory suggests that memories formed before the development of language and a strong sense of self lack the necessary framework for later retrieval. Without the ability to use language to organize and narrate an event, or without a clear concept of “me,” the memories cannot be stored in a way that the adult mind can later access. The brain does not yet possess the “filing system” required for autobiographical memory.