In the early 1960s, Sternberg published an original experiment demonstrating the mechanics of cognitive information processing. The experiment entails memorization of a positive set, a list of items such as numbers or words. The subject is then asked about a particular test item that may or may not have actually been present the set, and is asked to respond "yes" or "no" accordingly. The time taken for the subject to respond is recorded. This process is then repeated over several trials. What Sternberg found was that response time varied with the size of the positive set. In particular, response time tended to increase with the size of the list. This is significant because it demonstrates evidence for what is known today as the Serial Exhaustive Search Theory, which contends that when questioned regarding the presence of an item in a memory set, people will search every item in short-term memory without stopping, even if the item was found.