How big is human memory, or on being just useful enough.

We are, in many respects, what we remember. But how much do we do? So far, science has provided only a very partial answer to this riddle. The magical number seven, plus or minus two, seems to constrain the capacity of our immediate memory But surely its constraints dissipate when memories settle in long-term stores. Yet how big are these stores? If we combine all of our factual knowledge and personal reminiscence, childhood scenes and memories of the past day, intimate experiences and professional expertisemhow many items are there, that, combined together, mold us into unique individuals?