Can practice eliminate the psychological refractory period effect?

Can people learn to perform two tasks at the same time without interference ? To answer this question, the authors trained 6 participants for 36 sessio ns in a Psychological Refractory Period (PRP) experiment, where Task I requ ired a speeded vocal response to an auditory stimulus and Task 2 required a speeded manual response to a visual stimulus. The large PRP effect found i nitially (353 ms in Session 1) shrank to only about 40 ms over the course o f practice, disappearing entirely for 1 of the 6 participants. This reducti on in the PRP effect with practice is considerably larger than has been pre viously reported. The obtained pattern of factor interactions between stimu lus onset asynchrony and each of three task difficulty manipulations (Task 1 judgment difficulty, Task 2 stimulus contrast, and Task 2 mapping compati bility) supports a postponement (bottleneck) account of dual-task interfere nce, both before and after practice.