The Effect of Numeric Format on Probability Discounting Rates of Medical and Monetary Outcomes

  • Geraldine SmieszhalaEmail author
  • Anne C. Macaskill
  • Maree J. Hunt
Original Article


We assessed whether numeric format in the form of frequencies and percentages affects probability discounting rates in medical and monetary contexts across three experiments. Experiments 1 and 2 compared percentage (e.g., 10%) and frequency (e.g., 10 in 100) formats. Numeric format only affected discounting rates in the medical condition in Experiment 2. The lack of effect of numeric format on probability discounting of money was inconsistent with previous findings from Yi and Bickel (2005). Therefore, in Experiment 3 we more closely replicated their procedure. Results yielded no effect of numeric format on discounting rates. Across experiments, we concluded that probability discounting rates for monetary outcomes are not affected by whether they are presented in a frequency or percentage format. We also concluded that the effect of numeric format on probability discounting rates of medical outcomes is fragile, and unlikely to affect medical decision making in practice. Experiment 2 and 3 also examined whether the hyperbolic or hyperboloid model provided a more efficient description of probability discounting functions. Data were more efficiently described by the hyperbolic model in Experiment 2, and the hyperboloid model in Experiment 3.


Probability discounting Choice decision making Medical decision making Informed decision making Hyperbolic model Hyperboloid model 


Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Victoria University of Wellington and with the 1964 Helsinki declaration and its later amendments.

Informed Consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Association for Behavior Analysis International 2019

Authors and Affiliations

  1. 1.Victoria University of WellingtonWellingtonNew Zealand

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