A multiple structure model of processing resources (Wickens, 1980) guided construction of tasks of differential resource demand that were both performed by subjects and rated according to workload similarity. Analysis of performance data generally supported model predictions. Multidimensional scaling analysis of the similarity data produced subjective dimensions of workload that were explained in terms of resource demand and task structure.

Building upon previous research, this study examined the relationship between the deployment of spatial resources in the performance of spatial tasks and the level of spatial ability possessed by subjects. Ten Air Force Academy cadets, classified as either high or low in spatial ability by paper and pencil measures, performed tasks that presumably demanded spatial resources. Both the baseline and dual task level of performance was superior for the high spatial ability group. These findings are related to a variable capacity model of processing resources.

This article outlines three major assumptions often implicitly made in dual-task experiments conducted to assess attentional capacity requirements of memorial processes. These assumptions are shown to be incorrect. Three criteria which should be met in dual-task experiments that draw inferences from secondary task decrements are proposed: (1) there should be resource trade-off with the secondary task sensitive to the resource demands of the primary task; (2) there should be equivalence of single and dual primary task performance; and (3) the secondary task must remain resource sensitive throughout the experiment. An experiment was carried out in which the primary and secondary tasks were designed according to these criteria. The results demonstrate that when the criteria are met then secondary task performance can be predictive of primary task difficulty: however, the experiment also highlights the fact that a simple assessment of capacity will not predict total task performance.

Earlier work by Gopher, Brickner, and Navon (1982) suggested that evidence for multiple processing resources can be demonstrated only if both task difficulty and task priorities are manipulated in dual task studies. To further investigate their approach, ten subjects performed both single and dual task versions of a tracking task and a vowel insertion task, the latter modified to increase either motor load or cognitive load. Dual task trials required equal task emphasis on the favoring of one task over another. As expected, a difficulty by priority interaction was found in the motor load but not in the cognitive load condition, suggesting multiple resources. Performance Operating Characteristics for these data suggested that more than two resources were being utilized by these tasks.

The present paper outlines three major assumptions often implicitly assumed in dual task experiments conducted to assess operator workload. These assumptions are shown to be incorrect. Three criteria which should be met in dual task experiments that draw inferences from secondary task decrements are discussed. An experiment, meeting the proposed criteria, was conducted which demonstrated that when the criteria are met secondary task performance can be predictive of primary task difficulty. However, the data also indicate that a simple assessment of effort alone will not predict total task performance.

Multiple measures of operator workload may fail to agree or dissociate for a given task. This study proposes a new method to examine this dissociation for two categories of workload measures: Subjective ratings and performance-based secondary tasks. Eighteen tasks of differential processing resource demand were performed by subjects and rated according to workload similarity. Additive clustering analysis of the workload ratings produced overlapping task clusters. Three properties–performance, effort, and input complexity-explained the cluster solution. Dissociation was found when tasks perceived as similar in workload did not possess the same properties.

: Results from dual task experiments have often been used to make inferences concerning memorial processes. However, many dual task experiments are based on invalid methodological assumptions. Three major assumptions which are implicitly assumed by current dual task memory research are shown to be inappropriate. Criteria which should be met in dual task experiments that draw inferences from secondary task decrements are discussed. A dual task experiment meeting the proposed criteria was conducted. Contrary to previous dual task research, the present experiment demonstrates that a carefully controlled dual task experiment shows that primary task effort is neither monotonically related to levels of processing, nor does it produce better memory for verbal stimuli. It is concluded that researchers must carefully consider the assumptions inherent in any dual task experiment when designing such experiments. (Author)

Additive factors methodology was applied to dual task data to discover the pool of resources demanded when tracking bandwidth is increased. Ten subjects tracked signals of both low and high bandwidth and performed a cognitive loading task that was constructed to demand either central processing or response execution resources. The hypothesis that bandwidth increases demand response execution resources was not supported. Experimental methodology and control are discussed as possible reasons for the failure.

The processing resources enabling dual task performance are modeled as a vector quantity, with dimensions defined by processing stages, processing codes, and processing modalities. This multidimensional conception is employed to model operator workload and to predict task interference patterns, employing a Sternberg task methodology. The implications to time-sharing performance are addressed as they pertain to the stage dimensions (Experiment 1: Manual Tracking), the code dimension (Experiment 2: Failure detection), and the code and modality dimension (Experiment 3: Multi-element monitoring).