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

USER INTERFACE LABORATORY

Introduction

variations in the efficiency with which time-sharing can be carried out1. 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 (Broad-bend, 1958; Keele, 1973; Welford, 1967)

Processing Resources in Attention


Historical OverviewStructural 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-se-lection 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



Capacity Theories the measurement of human operator workload Knowles (1963) – a conceptual model of the human operator as pro-

cessing a “pool” of limited-capacity resources: primary-task workload inversely reflected in secondary-task performance divisibillity and al-location 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 op-

erator’s limited capacity (Rolfe, 1971) the concept of capacity or resources as an intervening variable in dual-

task performance



Resource TheoryDefining Elements capacity, attention, effort, resources

The Performance-Resource Function performance-resource function (PRF) in Fig 3.1

data-limited resource limited

allocation policies in Fig 3.2a1) subjects actually allocate resources as commanded2) resources deployed in performance of the two different tasks are

functionally equivalent and maximally effective for each task



The Performance of Operating Characteristic POC in Fig 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 3.3




• under single-task conditions, if one “tries harder” on a task, performance at least will not deteriorate and prob-ably will improve.

• under dual-task conditions, resource theory infers that the subject is modu-lating the supply of resources be-tween the tasks in order to obtain the desired levels of differential perfor-mance



cost of concur-rence(resource limited)

cost of concur-rence(data limited)

Time- shar-ing efficiency

Ideal multi-task performance

bias






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 eas-ier of the two tasks when it is paired with the third task



Multiple-Resource Theory1. 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 3.54. performance on a “primary” task for which the difficulty is varied can

be preserved through resource reallocation by sacrificing a sec-ondary task (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 re-sponse (manual versus vocal) in Fig 3.7









Applications of Multiple-Resource TheoryWorkload 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



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 per-

formance 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



Subjective Measures scalar measure because of the difficulty in introspectively diagnosing

the resource demands within a dimensional framework


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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