Attention, Resource Allocation, and Communication Research: What Do Secondary Task Reaction Times Measure, Anyway?

This chapter refines the conceptual and operational definitions underlying secondary task reaction times (STRTs) in an attempt to clarify exactly what STRTs measure. The intent is to make the measure more useful to researchers studying changes in attention and effort during communication activities. Perusal of the communication literature yields four frequently stated operational definitions of what STRTs measure: (a) the resources required by a message, (b) the resources allocated to the message, (c) the resources available for processing, and (d) the resources remaining in the system. It is demonstrated that these pieces of the resource pie do not always covary. It is suggested that the published research best supports the interpretation of STRTs as available resources. However, interpreting STRTs as available resources cannot explain instances found in the literature where STRTs are fast and memory for messages is slow. A further modification of the model is proposed that involves integrating the limited-capacity approach to television viewing with the four definitions of the STRT. This integration yields a model that interprets STRTs as an index of resources available to the encoding subprocess and interprets memory as an index of resources available at storage. This model is then used to predict the effects of the various independent variables found in the published research on STRTs and memory. The model accurately predicts 16 out of the 20 (84%) of the results of published reaction time studies and 12 out of 14 (85%) of the published tests of memory performance.