figure 6.3 Short-term memory decay Memory decays rapidly from short-term memory. On the second and third trials of a task in which people try to remember a series of letters or numbers, information significantly decays within 20 seconds. However, on the first trial of a memory experiment, information is retained—there is no decay in 20 seconds. This indicates that forgetting results from not only decay, but also proactive interference. At the start of a study, when no prior information has been learned, there is no proactive interference, and memory performance is excellent.