1. U SER I NTERFACE L ABORATORY Introduction  variations in the efficiency with which time-sharing can be carried out 1.the concept of processing resources 2.the concept of structure  two classes of theories of attention: capacity theories (Kahneman, 1973; Knowles, 1963; Moray, 1967) and structural theories (Broadbend, 1958; Keele, 1973; Welford, 1967) Processing Resources in Attention

2. U SER I NTERFACE L ABORATORY Historical Overview Structural Theories  dichotic listening task – bottleneck in human information processing?  early selection theories that considered the bottleneck to occur at perception (e.g., Broadbent, 1958; Treisman, 1969) and late- selection theories to initiate a response  psychological refractory period paradigm and a dual-task paradigm – late-selection theories – bottleneck at the stage of response initiation  the focus on differences in task structure (primarily related to stages of processing) that impact on dual-task performance efficiency Processing Resources in Attention

3. U SER I NTERFACE L ABORATORY Capacity Theories  the measurement of human operator workload  Knowles (1963) – a conceptual model of the human operator as processing a “pool” of limited-capacity resources: primary-task workload inversely reflected in secondary-task performance  divisibillity and allocation properties  Moray (1967) – the source of interference would depend merely on the capacity demand at any particular stage of processing  Taylor et al. (1967) – the sharability of attention  workload is proportional to the demands imposed by tasks on the operator’s limited capacity (Rolfe, 1971)  the concept of capacity or resources as an intervening variable in dual- task performance Processing Resources in Attention

4. U SER I NTERFACE L ABORATORY Resource Theory Defining Elements  capacity, attention, effort, resources The Performance-Resource Function  performance-resource function (PRF) in Fig 3.1Fig 3.1  data-limited  resource limited  allocation policies in Fig 3.2aFig 3.2a 1)subjects actually allocate resources as commanded 2)resources deployed in performance of the two different tasks are functionally equivalent and maximally effective for each task Processing Resources in Attention

5. U SER I NTERFACE L ABORATORY The Performance of Operating Characteristic  POC in Fig 3.2bFig 3.2b Single-Task Performance Time-sharing Efficiency Degree of a Linear Exchange Allocation Bias Efficiency and Allocation in Combination Automation and Task Difficulty  the effects of practice and task difficulty in Fig 3.3Fig 3.3 Processing Resources in Attention

6. U SER I NTERFACE L ABORATORY Processing Resources in Attention under single-task conditions, if one “tries harder” on a task, performance at least will not deteriorate and probably will improve. under dual-task conditions, resource theory infers that the subject is modulating the supply of resources between the tasks in order to obtain the desired levels of differential performance

7. U SER I NTERFACE L ABORATORY Processing Resources in Attention cost of concurrence (resource limited) cost of concurrence (data limited) Time- sharing efficiency Ideal multi-task performance bias

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10. U SER I NTERFACE L ABORATORY Limitations of Single-Resource Theory Difficulty Insensitivity  increases in difficulty or demand of a primary task fail to influence the performance of a secondary task Perfect Time-sharing Structural Alteration Effects  instances in which the change in a processing structure brings about a change in interference with a concurrent task Uncoupling of Difficulty and Structure  instances in which the more difficult of two tasks when paired with a third task actually interferes less with the third task than does the easier of the two tasks when it is paired with the third task Processing Resources in Attention

11. U SER I NTERFACE L ABORATORY Multiple-Resource Theory 1.two tasks demand separate rather than common resources, they will be time-shared efficiently. 2.tasks share common resources, a relatively smooth POC can be generated between them. if not, the POC will be “boxlike”. 3.difficulty insensitivity in Fig 3.5Fig 3.5 4.performance on a “primary” task for which the difficulty is varied can be preserved through resource reallocation by sacrificing a secondary task (Fig 3.6)Fig 3.6  Wickens (1980) argued that resources as a 3D metric consisting of stages of processing (perceptual-central versus response), codes of perceptual and central processing (verbal versus spatial) and response (manual versus vocal) in Fig 3.7Fig 3.7 Processing Resources in Attention

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15. U SER I NTERFACE L ABORATORY Applications of Multiple-Resource Theory Workload Assessment  inversely related to the percentage of “residual capacity” not allocated to a primary task Primary-Task Parameters  task workload, task-difficulty manipulation, task performance  the measure should reflect resources imposed by task performance both on encoding and central processing and on responses of a verbal and spatial nature  absolute workload imposed by a task – primary-task workload margin Processing Resources in Attention

16. U SER I NTERFACE L ABORATORY The Secondary-Task Technique  inversely proportional to the primary-task resource demands  interference and disruption that it often causes with the primary task Primary- versus Secondary-Task Measures  one major advantage of the secondary-task measure – changes in performance of the secondary task measure clearly reflect changes in the resource demand of the primary task measure Physiological Measures  scalar measure  diagnosticity and sensitivity – pupil diameter, heart rate variability  ERP sacrifices the global sensitivity Processing Resources in Attention

17. U SER I NTERFACE L ABORATORY Subjective Measures  scalar measure because of the difficulty in introspectively diagnosing the resource demands within a dimensional framework Processing Resources in Attention