Everybody has a story to tell. For most of us, it’s the places we’ve been,
the people we’ve known and the experiences we’ve had that make us
who we are. This sense of ourselves, as a character at the heart of an
unfolding narrative, would be impossible without memory. In biolog-
ical terms, memory is reflected in the endlessly changing patterns and
strengths of connectivity between brain cells. One of psychology’s
most important contributions in this field has been to catalogue and
define the different types of memory and the way they function.
Defining memories
The story of our lives depends on autobiographical memory (also known
as episodic memory), a form of long-term storage that provides a coherent
record of where we’ve been, what we’ve done and who we’ve known.
Another kind of long-term memory is called semantic memory, which
stores all the facts we know about the world, such as the name of the
capital of France. Yet another form relates to the skills we’ve learned, such
as riding a bike or driving a car, and this is known as procedural memory.
Then there is our short-term memory, one form of which is usually
described as working memory, reflecting the fact that it’s involved in
processing, not just storage. Working memory allows us to keep a mental
note while we perform a calculation or task, such as remembering a phone
number just before we dial, or keeping our choice in mind before giving an
order to the waiter. Working memory is usually thought of as having three
parts: a visual component, rather like the note pad you keep by the phone; a
sound component, which is like a limited-storage dictaphone; and a central
executive, which supervises and delegates to the first two components.
A classic psychology study from the 1950s by George Miller established
that most people’s short-term storage capacity is limited to seven items,
“plus or minus two”. This limit applies to chunks of information, so