Psychological Refractory Period

Modern production systems, such as EPIC (for executive-process interactive control) (Meyer & Kieras, 1997a, 1997b), have evolved to include sensing and acting.  EPIC simulates the performance of  multiple tasks, and can produce the psychological refractory period (PRP).  When two tasks can be performed at the same time, the stimulus onset asynchrony (SOA) between the tasks is the length of time from the start of the first task the start of the second task.  When SOAs are long, the time taken by a subject to make a response is roughly the same for both tasks.  However, for SOAs of half a second or less, it takes a longer time to perform the second task than it does to perform the first.  This increase in response time for short SOAs is the PRP.

References:

1. Meyer, D. E., & Kieras, D. E. (1997a). A computational theory of executive cognitive processes and multiple-task performance .1. Basic mechanisms. Psychological Review, 104(1), 3-65.
2. Meyer, D. E., & Kieras, D. E. (1997b). A computational theory of executive cognitive processes and multiple-task performance .2. Accounts of psychological refractory-period phenomena. Psychological Review, 104(4), 749-791.

(Added October 2010)