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Full Title

Time design: The analysis of subjective time


Time, decision-making


Time plays an essential role in almost every aspect of developing and running socio-technical systems. For instance, acceleration is one of the main drivers of technological innovation; work processes become increasingly dynamic and require on-the-spot replanning; coordination, synchronisation and timeliness are essential requirements in diverse systems; decisions are often taken under acute time pressure. Where time is considered in design decisions, it is usually viewed as an external constraint (deadline view), as a descriptive property of behaviour (epiphenomenal view), as a stressor acting on the human operator, or as a variable that is to be controlled or optimized.

More recently, there has been a growing interest in a functional view of time supported by research into higher-level aspects of temporal decision-making (cf. Varey and Kahneman, 1992; De Keyser, 1995). A functional, or causal, view of time explores the ways in which human control behaviour is sensitive to temporal information and temporal knowledge, what heuristics and biases occur in temporal control decisions, and how temporal aspects of the system constitute degrees of freedom that the operator can use to make adaptive control decisions. Such problems lead us away from assigning objective time tags to human behaviour (as in descriptive approaches) and towards considering how we can design for subjective time, i.e. for the way humans perceive, attend to, process, and control temporal features of their environment.

DIRC has made the following contributions to this approach:

Several interdisciplinary workshops have been organized to define the scope and content of the Time Design approach, to identify sources of error perceiving and processing subjective time, and to define a research agenda to address these problems (e.g. Hildebrandt, Dix and Meyer, 2004; Hildebrandt and Rantanen, 2004).

We developed a series of microworld simulations (PumpPlant, PaintShop, both require MSIE; When-to-act, requires Firefox) that capture different aspects of temporal decision-making, such as human scheduling performance, use of temporal information (Hildebrandt and Harrison, 2004), time-accuracy trade-offs, and temporal uncertainty. For some of these simulations, formal models have been developed to provide a normative standard against which human performance can be compared (Loer, Hildebrandt and Harrison, 2004; Hildebrandt and Meyer, 2005). The suite of microworld simulations is available to researchers as tools for exploring related problems.

We have argued that current models of adaptive automation, such as Dynamic Function Allocation, fail to take account of the most common workload balancing strategy, namely allocation of functions in time. The Dynamic Function Scheduling approach aims to support system designers in considering function management as allocation of functions both in time and among agents (Hildebrandt and Harrison, 2002, 2003).


Time Design website

Research summary When to act

Research summary Time and context modelling

Microworld PumpPlant [requires MSIE]

Microworld PaintShop [requires MSIE]

Microworld When-to-act [requires Firefox]

Research theme Timeliness



Hildebrandt, M. & Harrison, M.D. (2003). Putting time (back) into Dynamic Function Allocation. Proceedings of the 47th Annual Meeting of the Human Factors and Ergonomics Society (pp.488-492).

Hildebrandt, M., Dix, A. & Meyer, H.A. (2004). Time design. In E. Dykstra-Erickson & M. Tscheligi (Eds.), CHI 2004 Conference on Human Factors in Computing Systems (Extended Abstracts, pp. 1737-1738). New York: ACM Press.

Hildebrandt, M. & Harrison, M.D. (2004). PaintShop: A Microworld Experiment Investigating Temporal Decisions in a Supervisory Control Task. Proceedings of the 48th Annual Meeting of the Human Factors and Ergonomics Society (pp. 300-304).

Hildebrandt, M. & Harrison, M.D. (2002). Time-related trade-offs in Dynamic Function Scheduling. In C. Johnson (Ed.). Proceedings of the 21st European Annual Conference on Human Decision Making and Control (pp. 89-95).

Hildebrandt, M., and Meyer, J. (2005). When to act? Managing time-accuracy trade-offs in a dynamic belief updating task. In Proceedings of the 49th Annual Meeting of the Human Factors and Ergonomics Society.

Hildebrandt, M. & Rantanen, E. (2004). Time Design. Proceedings of the 48th Annual Meeting of the Human Factors and Ergonomics Society (pp. 703-707).

Loer, K.F., Hildebrandt, M. & Harrison, M.D. (2004). Analysing dynamic function scheduling decisions. Proceedings of IFIP 13.5 Working Conference on Human Error, Safety and Systems Development.

Meyer, H.A. & Hildebrandt, M. (2002). Towards Time Design: Pacing of hypertext navigation by system response times. In L. Terveen & D. Wixon (Eds.), CHI 2002 Conference on Human Factors in Computing Systems (Extended Abstracts, pp. 824-825). New York: ACM Press.

Other references

Card, S., Moran, T. P., and Newell, A. (1980). The keystroke-level model for user performance with interactive systems, Communications of the ACM, 23, 396-210.

De Keyser, V. (1995). Time in ergonomics research. Ergonomics, 38, 1639-1660.

Varey, C. & Kahneman, D. (1992). Experiences extended across time: Evaluation of moments and episodes. Journal of Behavioral Decision Making, 5, 169-185.


Michael Hildebrandt [hilde at cs dot york dot ac dot uk]


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