Blackburn & El-Deredy (2013) provide a nice review of the literature on temporal (delay) and probabilistic discounting. They note these features of similarity and difference:
- Both follow hyperbolic (rather than exponential) discount functions
- Not correlated: impulsivity might be interpreted as steeper temporal discounting, and shallower probabilistic discounting, but steep temporal discounters don’t appear to be shallow probabilistic discounters
- Magnitude effect opposite: for probabilistic rewards, larger rewards are more steeply discounted, for delayed rewards, larger rewards are more shallowly discounted
- Sign effect the same: Gains vs loses effect discounting similarly for temporal and probabilistic discounting (gains are more steeply discounted).
To this list their experiments add a dissociable effect of ‘uncertain outcomes’ (all or nothing) vs ‘uncertain amounts’ (graded reward).
Blackburn, M., & El-Deredy, W. (2013). The future is risky: Discounting of delayed and uncertain outcomes. Behavioural processes, 94, 9-18.
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[…] 1. Laude et al (2014) showed that for individual pigeons there was a correlation between degree of suboptimal choice on a gambling task (overweighting of rare but large rewards) and impulsivity as measured by a delay discounting task. As well as seeming to show ‘individual differences’ in pigeon personality, it suggests the possibility of some common factors in these two kinds of choices (choices which experimental human work has found to be dissociable in various ways) […]