The psychological refractory period (PRP) is a basic but important form of dual-task information processing. Existing serial or parallel processing models of PRP have successfully accounted for a variety of PRP phenomena; however, each also encounters at least 1 experimental counterexample to its predictions or modeling mechanisms. This article describes a queuing network-based mathematical model of PRP that is able to model various experimental findings in PRP with closed-form equations including all of the major counterexamples encountered by the existing models with fewer or equal numbers of free parameters. This modeling work also offers an alternative theoretical account for PRP and demonstrates the importance of the theoretical concepts of "queuing" and "hybrid cognitive networks" in understanding cognitive architecture and multitask performance.Keywords: psychological refractory period (PRP), cognitive architecture, queuing network, multitask performance, serial and parallel processing Performing multiple tasks at the same time is common in daily life; for example, drivers can steer a car and at the same time talk with friends in the car, and telephone operators can answer customer phone calls and type textual information into a computer. Among the wide range of multiple task situations, the psychological refractory period (PRP) is one of the most basic and simplest forms of a dual-task situation. In a PRP experiment, two reactiontime (RT) tasks are presented close together in time, and participants are asked to perform the two tasks as quickly as possible. Typically, participants' response to the second of the two RT tasks is performed more slowly than to the first when the interval between the presentation times of these two tasks is short. PRP has been studied in laboratories over 100 years, from the behavioral (Creamer, 1963;Kantowitz, 1974;Oberauer & Kliegl, 2004;Pashler, 1984Pashler, , 1994bSchumacher et al., 1999;Solomons & Stein, 1896;Welch, 1898;Welford, 1952) to the neurological level (Jiang, Saxe, & Kanwisher, 2004;Sommer, Leuthold, & Schubert, 2001). It is also the subject of extensive theoretical work and the focal point of an important theoretical controversy between several computational models of cognition. There are several important cognitive models of PRP, including the response-selection bottleneck (RSB) or central bottleneck model proposed by Pashler (1984Pashler ( , 1990Pashler ( , 1994aPashler ( , 1994bPashler ( , 1994c, the executive-process interactive control (EPIC) model proposed by Kieras (1997a, 1997b), and the model based on the ACT-R/perceptual-motor system (ACT-R/PM) proposed by Byrne and Anderson (2001). Each of these models is able to account for some of the important aspects of PRP; however, each appears to encounter at least one experimental counterexample to its predictions (Jiang et al., 2004;Meyer & Kieras, 1997a, 1997bOberauer & Kliegl, 2004;Ruthruff, Pashler, & Klaassen, 2001). Therefore, the questions remain about how to model these experimental results, provide...