Memory & Cognition

, Volume 36, Issue 4, pp 791–798 | Cite as

Allocating time to future tasks: The effect of task segmentation on planning fallacy bias

  • Darryl K. Forsyth
  • Christopher D. B. BurtEmail author


The scheduling component of the time management process was used as a (“paradigm”) to investigate the allocation of time to future tasks. In three experiments, we compared task time allocation for a single task with the summed time allocations given for each subtask that made up the single task. In all three, we found that allocated time for a single task was significantly smaller than the summed time allocated to the individual subtasks. We refer to this as the segmentation effect. In Experiment 3, we asked participants to give estimates by placing a mark on a time line, and found that giving time allocations in the form of rounded close approximations probably does not account for the segmentation effect. We discuss the results in relation to the basic processes used to allocate time to future tasks and the means by which planning fallacy bias might be reduced.


Time Allocation Future Task Software Effort Estimation Spelling Mistake Phone Bill 
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  1. Armstrong, J. S., Denniston, W. B., & Gordon, M. M. (1975). The use of the decomposition principle in making judgments. Organizational Behavior & Human Decision Processes, 14, 257–263.Google Scholar
  2. Berkeley, D., & Humphreys, P. (1982). Structuring decision problems and the (“bias heuristic.”) Acta Psychologica, 50, 201–252.CrossRefGoogle Scholar
  3. Block, R. A., & Zakay, D. (1997). Prospective and retrospective duration judgments: A meta-analytic review. Psychonomic Bulletin & Review, 4, 184–197.Google Scholar
  4. Buehler, R., Griffin, D., & MacDonald, H. (1997). The role of motivated reasoning in optimistic time predications. Personality & Social Psychology Bulletin, 23, 238–247.CrossRefGoogle Scholar
  5. Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the (“planning fallacy”): Why people underestimate their task completion times. Journal of Personality & Social Psychology, 67, 366–381.CrossRefGoogle Scholar
  6. Burt, C. D. B., & Forsyth, D. (1999). Designing materials for efficient time management: Segmentation and planning space. Cognitive Technology, 4, 11–18.Google Scholar
  7. Burt, C. D. B. & Kemp, S. (1994). Construction of activity duration and time management potential. Applied Cognitive Psychology, 8, 155–168.CrossRefGoogle Scholar
  8. Byram, S. J. (1997). Cognitive and motivational factors influencing time prediction. Journal of Experimental Psychology: Applied, 3, 216–239.CrossRefGoogle Scholar
  9. Claessens, B. J. C., Van Eerde, W., Rutte, C. G., & Roe, R. A. (2004). Planning behavior and perceived control of time at work. Journal of Organizational Behavior, 25, 937–950.CrossRefGoogle Scholar
  10. Eisler, H. (1976). Experiments on subjective duration 1868-1975: A collection of power function exponents. Psychological Bulletin, 83, 1154–1171.CrossRefPubMedGoogle Scholar
  11. Francis-Smythe, J. A., & Robertson, I. T. (1999). On the relationship between time management and time estimation. British Journal of Psychology, 90, 333–347.CrossRefGoogle Scholar
  12. Grimstad, S., Jørgensen, M., & Moløkken-Østvold, K. (2006). Software effort estimation terminology: The tower of Babel. Information & Software Technology, 48, 302–310.CrossRefGoogle Scholar
  13. Henrion, M., Fischer, G. W. & Mullin, T. (1993). Divide and conquer? Effects of decomposition on the accuracy and calibration of subjective probability distributions. Organizational Behavior & Human Decision Processes, 55, 207–227.CrossRefGoogle Scholar
  14. Hora, S. C., Dodd, N. G., & Hora, J. A. (1993). The use of decomposition in probability assessment of continuous variables. Journal of Behavioral Decision Making, 6, 133–147.CrossRefGoogle Scholar
  15. Hornik, J. (1981). Time cue and time perception effect on response to mail survey. Journal of Marketing Research, 18, 243–248.CrossRefGoogle Scholar
  16. Huttenlocher, J., Hedges, L. V., & Bradburn, N. M. (1990). Reports of elapsed time: Bounding and rounding processes in estimation. Journal of Experimental Psychology: Learning, Memory, & Cognition, 16, 196–213.CrossRefGoogle Scholar
  17. Jørgensen, M. (2004). Top-down and bottom-up estimation of software development effort. Information & Software Technology, 46, 3–16.CrossRefGoogle Scholar
  18. Kahneman, D., & Tversky, A. (1979). Intuitive prediction: Biases and corrective procedures. TIMS Studies in Management Science, 12, 313–327.Google Scholar
  19. Kruger, J., & Evans, M. (2004). If you don’t want to be late, enumerate: Unpacking reduces the planning fallacy. Journal of Experimental Social Psychology, 40, 586–598.CrossRefGoogle Scholar
  20. Macan, T. M. (1994). Time management: Test of a process model. Journal of Applied Psychology, 79, 381–391.CrossRefGoogle Scholar
  21. MacGregor, D. G., & Armstrong, J. S. (1994). Judgmental decomposition: When does it work? International Journal of Forecasting, 10, 495–506.CrossRefGoogle Scholar
  22. Newby-Clark, I. R., Ross, M., Buehler, R., Koehler, D. J., & Griffin, D. (2000). People focus on optimistic scenarios and disregard pessimistic scenarios while predicting task completion times. Journal of Experimental Psychology: Applied, 6, 171–182.CrossRefPubMedGoogle Scholar
  23. Oden, G. (1987). Concept, knowledge, and thought. Annual Review of Psychology, 38, 203–227.CrossRefGoogle Scholar
  24. Roy, M. M., Christenfeld, N. J. S., & McKenzie, C. R. M. (2005). Underestimating the duration of future events: Memory incorrectly used or memory bias? Psychological Bulletin, 131, 738–756.CrossRefPubMedGoogle Scholar
  25. Schank, R. C., & Abelson, R. P. (1977). Scripts, plans, goals, and understanding: An inquiry into human knowledge structures. Hillsdale, NJ: Erlbaum.Google Scholar
  26. Smith, E. E., & Medin, D. L. (1981). Categories and concepts. Cambridge, MA: Harvard University Press.Google Scholar
  27. Zakay, D. (1990). The evasive art of subjective time measurement: Some methodological dilemmas. In R. A. Block (Ed.), Cognitive models of psychological time (pp. 59–84). Hillsdale, NJ: Erlbaum.Google Scholar

Copyright information

© Psychonomic Society, Inc. 2008

Authors and Affiliations

  1. 1.Department of PsychologyUniversity of CanterburyChristchurchNew Zealand
  2. 2.Massey UniversityAucklandNew Zealand

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