Virtually perfect time sharing in dual-task performance: uncorking the central cognitive bottleneck.

A fundamental issue for psychological science concerns the extent to which people can simultaneously perform two perceptual-motor tasks. Some theorists have hypothesized that such dual-task performance is severely and persistently constrained by a central cognitive "bottle-neck," whereas others have hypothesized that skilled procedural decision making and response selection for two or more tasks can proceed at the same time under adaptive executive control. The three experiments reported here support this latter hypothesis. Their results show that after relatively modest amounts of practice, at least some participants achieve virtually perfect time sharing in the dual-task performance of basic choice reaction tasks. The results also show that observed interference between tasks can be modulated by instructions about differential task priorities and personal preferences for daring (concurrent) or cautious (successive) scheduling of tasks. Given this outcome, future research should investigate exactly when and how such sophisticated skills in dual-task performance are acquired.

Using response time measures to assess "guilty knowledge".

How can a suspect's guilt or innocence be reliably tested? The validity of the polygraph, which measures changes in physiological arousal during a "guilty knowledge" test, is controversial (e.g., T. R. Bashore & P. E. Rapp, 1993; T. P. Cross & L. Saxe, 1992; D. T. Lykken, 1998; J. P. Rosenfeld, 1995; R. Steinbrook, 1992). One alternative to the polygraph examines event-related potentials recorded during a memory interference task (L. A. Farwell & E. Donchin, 1991). The present study extended this paradigm to determine whether response times (RTs) can accurately identify participants possessing specific guilty knowledge. Results from Experiment 1 showed that RT alone can reliably discriminate "guilty" from "innocent" participants. Experiments 2a and 2b indicated that an RT-based paradigm is more resistant to strategic manipulation than previously suggested (Farwell & Donchin, 1991). This RT-based paradigm may be a viable alternative to the polygraph for detecting guilty knowledge.