Short-term memory is mainly related to the activity of neurons and the relationship between neurons. In particular, it is related to a brain area under the cerebral cortex that looks like hippocampus, and long-term memory is mainly related to the establishment of new synapses. The most important feature of short-term memory is that the information retention time is quite limited. Without retelling, most information is kept in short-term memory for a short time, usually 5-20 seconds, and the longest time is no more than 1 minute. Short-term memory is sometimes called phone number memory, just like people dial the phone number immediately after finding it, and then forget it immediately after making the call.

The second key concept related to short-term memory is its capacity, also known as memory span. The capacity of short-term memory is very limited. 1956, American psychologist G. Miller published a paper entitled "magic number 7 plus or minus 2: some limitations of our ability to process information". According to the experimental results of randomly repeating a table with 3 to 12 digits, it is found that the maximum amount of short-term memory that subjects can recall after a presentation of information-the capacity of short-term memory is generally 7 2 units. Children's memory span is more limited, usually 4 1 unit. The short-term memory span measured by China scholars is that unrelated Chinese characters can remember 6 words, 7 decimals and 5 lines at a time.