The earliest of explicit learning is evidenced at birth. Explicit learning as noted in the PTSD section (i.e. PTSD/MEMORY/Explicit-Declarative Memory, is memory that is in awareness and declarable. Infants as early as birth can recognize and retrieve facial expressions from a few hours to one day later. The act of deliberate retrieval is an explicit-declarative process. Elicited imitation and delayed non-match-to-sample require explicit and declarative processes. The ability to master the earliest most rudimentary tasks is evidenced as early as 4-6 months are also evidenced as early as months. Both tasks require retrieval. Research on infant learning suggests very early that infants area able to retrieve memory from birth onward. This is suggestive of viable neocortex-hippocampal formation interactions.