Attention in character-classification tasks: Evidence for the automaticity of component stages.

Most theories of attention predict that engaging a subject in demanding concurrent activity will increase choice reaction time by an amount proportional to the attention demands of the choice task. The attention demands of mental operations within the choice task can be assessed by extending Sternberg's additivefactors method. Parameters associated with those processing stages that demand attention will interact with the amount of concurrent activity (i.e., will have greater effects with concurrent activity than without), but parameters associated with automatic processing stages will not (i.e., the joint effects will be additive). This analysis was applied to eight character-classification experiments. The classification task was either performed alone or in the retention interval of a short-term memory task which required ordered recall of 7 digits. According to the extended additive-factors method, the important effects are the interactions of classification-task parameters with memory load. The first two experiments reported validate the method with a memory-search task. Interactions were obtained between memory load and target-set size whose