On the use of a concurrent memory load to measure attention and automaticity.

The concurrent-memory-load technique identifies attention demands with interactions between reaction-time-task parameters and the size of the load on memory. Three experiments are reported in which a multiple-choice, reaction time task involving two, four, and eig-ht stimulus-response (S-R) alternatives was performed alone and in the retention interval of a short-termmemory task involving ordered recall of eight digits. In Experiment 1, assignment of stimulus letters to response buttons (S-R mapping) was consistent for 6 days but varied on the seventh. Memory load and number of alternatives interacted early in practice, but the interaction diminished over days, and the effects were additive on Day 6. When the S-R mapping changed on Day 7, the interaction returned. In Experiment 2, S-R mapping varied daily for 6 days, and the interaction remained stable throughout practice. In Experiment 3, S-R mapping was consistent for 6 days and varied on the seventh, but the memory task was not introduced until Days 6 and 7. The interaction between memory load and number of alternatives was stronger on