Some of the first noted research on human memory was conducted in 1890 by William James. Based on his works, James assumed memory consists out of two systems:

• primary memory, which lasts for a few seconds and holds in our consciousness the perception of events in our environment, and
• second memory, which has unlimited duration and can be brought to consciousness if wanted.

A measure for the capacity of short-term memory was first introduced in 1887 by Joseph Jacobs, who tested the span of digits his students were able to remember.

Famous People and Their Contributions to the Study of Memory Retrieved March 16, 2011.