studies of boxers revealed that a concussive blow to the head could bring on retrograde amnesia, erasing all memories stored during the preceding few minutes or hours while leaving older memories intact. The same phenomenon was noted in epileptics after they suffered seizures. Such observations implied that a memory, even a strong one, remains unstable for a brief period after it’s formed. A certain amount of time seemed to be required for a primary, or short-term, memory to be transformed into a secondary, or long-term, one.
