SCHEDULING PROCESSES IN WORKING-MEMORY - INSTRUCTIONS CONTROL THE ORDER OF MEMORY-SEARCH AND MENTAL ARITHMETIC

Humans must often use working memory to execute processes one at a tim e because of its limited capacity. Two experiments tested where limits in access to working memory occur. Subjects searched a short-term mem ory set for one stimulus digit and performed mental arithmetic with an other stimulus digit. In one experiment, they were told to carry out t he mental arithmetic before the memory search and to make the arithmet ic response first. In the other, they were instructed to perform the t asks in the opposite order. The overt responses were executed in the p rescribed order. Moreover, the covert working memory processes were ex ecuted in the prescribed order, as revealed by a critical path network analysis of reaction times. Results are explained in terms of a doubl e-bottleneck model in which central processes and responses are constr ained to be carried out for one task at a time.