How might memory be influenced by internal and external factors?

Short-term and long-term memory can be influenced by both
internal and external factors.  The time and place where the memory occurred can have an
impact on its formation.  Internal factors affecting memory have to do with the neurons
in the brain.  If the brain is not developed, such as a in a baby, or is deteriorating,
such as in an older person, then the memory may not fully form.  Conditions in the
person, such as someone who is tired or scared, can also have an impact.  Adrenaline can
impact memory formation.

External factors involving memory
can include sensory input.  Smell is  a particularly strong association in memory
formation.  Other factors might include the social conditions (who a person was with),
location and even time.