Short - term memory (or "primary '' or "active memory '') is the capacity for holding, but not manipulating, a small amount of information in mind in an active, readily available state for a short period of time. The duration of short - term memory (when rehearsal or active maintenance is prevented) is believed to be in the order of seconds. The most commonly cited capacity is The Magical Number Seven, Plus or Minus Two (which is frequently referred to as Miller 's Law), despite the fact that Miller himself stated that the figure was intended as "little more than a joke '' (Miller, 1989, page 401) and that Cowan (2001) provided evidence that a more realistic figure is 4 ± 1 units. In contrast, long - term memory can hold an indefinite amount of information.
who determined the capacity of short term memory
Cowan