Base-rate neglect as a function of base rates in probabilistic contingency learning.
People stick to cue frequency and shrug at base rates, so you must engineer the environment to show the real odds.
01Research in Context
What this study did
Kutzner et al. (2008) asked adults to learn which cue predicted an outcome. The real odds depended on base rates, but the cue popped up often or rarely.
Each person worked alone at a computer. Trials kept coming, and feedback arrived right after every choice.
What they found
People ignored the true odds. They guessed based on how often they saw the cue, not on the hidden base rate.
The bias showed up every time, even when the cue and outcome shared only the base-rate link.
How this fits with other research
Fraley (1998) had already argued that operant setups can catch fallacies like this. Florian et al. give the clean numbers that prove the point.
Savastano et al. (1994) saw a similar slip with humans on concurrent ratio-interval schedules. Folks leaned toward the richer schedule even when it paid less, echoing the new base-rate neglect.
Spanoudis et al. (2011) showed pigeons rapidly shifting choice when reinforcer odds changed. Humans in Florian’s lab did the same, chasing predictor frequency instead of maximizing payoff.
Why it matters
If your client keeps picking a response because it “feels common,” check the real contingency. Program extra trials that make the true odds obvious, and give immediate feedback to brake the frequency bias.
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02At a glance
03Original abstract
When humans predict criterion events based on probabilistic predictors, they often lend excessive weight to the predictor and insufficient weight to the base rate of the criterion event. In an operant analysis, using a matching-to-sample paradigm, Goodie and Fantino (1996) showed that humans exhibit base-rate neglect when predictors are associated with criterion events through physical similarity. In partial replications of their studies, we demonstrated similar effects when the predictors resembled the criterion events in terms of similarly skewed base rates. Participants' predictions were biased toward the more (or less) frequent criterion event following the more (or less) frequent predictor. This finding adds to the growing evidence for pseudocontingencies (Fiedler & Freytag, 2004), a framework that stresses base-rate influences on contingency learning.
Journal of the experimental analysis of behavior, 2008 · doi:10.1901/jeab.2008.90-23