The ultra-short-term memory
First, the information enters our ultra-short-term memory, a kind of buffer in which all the information reaching our senses is buffered shortly. The period in which the information is stored is about 0.1 to 2 seconds. This is the result of different tests and studies.
The German mathematician, physicist and physician, Johann Andreas von Segner, already dealt with the ultra-short-term memory in 1740. It is said that in his ultra-short-term memory experiment, he attached a glowing coal to a cartwheel and rotated the wheel in a dark room. The wheel increased in speed. The probands were supposed to say from which moment on they no longer perceived a single lump of coal but rather an unbroken circle of light. This transitional moment was Segner's basis of calculation of the duration of the ultra-short-term memory store. This duration amounted to 0,1 to 0,5 seconds. The brain can only perceive an unbroken circle if it is able to recall the location of the point during a certain period.
The American George Sperling performed another experiment in 1960. He asked probands to look at a matrix with several rows of letter at varying time intervals. Then he removed a row and asked the probands to recall the missing row. He found out that memories quickly fade. The procedure demonstrated that the ultra-short-term memory is able to store information for a period from 15 milliseconds to about 2 seconds.