Document Type




Format of Original

7 p.

Publication Date



Taylor & Francis

Source Publication

Theoretical Issues in Ergonomic Science

Source ISSN


Original Item ID

doi: 10.1080/1463922X.2011.552131


We reconceptualised several problems concerning the measurement of cognitive workload – fixed versus variable limits on channel capacity, work volume versus time pressure, adaptive strategies, resources demanded by tasks when performed simultaneously, and unclear distinctions between workload and fatigue effects – as two cusp catastrophe models: buckling stress resulting from acute workload, and fatigue resulting from extended engagement. Experimental participants completed a task that was intensive on non-verbal episodic memory and had an automatically speeded component. For buckling stress, the epoch of maximum (speeded) performance was the asymmetry parameter; however, anxiety did not contribute to bifurcation as expected. For fatigue, the bifurcation factor was the total work accomplished, and arithmetic, a compensatory ability, was the asymmetry parameter; R2 for the cusp models outperformed the linear comparison models in both cases. A research programme is outlined that revolves around the two models with different types of task and resource configurations.


Accepted version. Theoretical Issues in Ergonomics Science, Vol. 13, No. 5 (2012): 586-602, DOI. © 2012 Taylor & Francis. Used with permission.

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