Human symbolic matching-to-sample performance: Effects of reinforcer and sample-stimulus probabilities.
Reinforcer ratio and sample probability both tug at human matching-to-sample choices—balance them or bias walks in.
01Research in Context
What this study did
Adults without disabilities did symbolic matching-to-sample tasks on a computer.
The team changed two things: how often each sample appeared and how often choosing it paid off.
They ran four small lab tests to see which factor pulled the learner’s finger more.
What they found
When sample odds stayed the same but reinforcer odds shifted, choice bias moved with the money.
When both odds changed together, the picture got messy—sometimes the money won, sometimes the frequency won.
Bottom line: both the pay-off schedule and the sample lottery ticket shape what people pick.
How this fits with other research
Reberg et al. (1979) showed the same reinforcer bias in pigeons years earlier, so the effect crosses species.
Thrailkill et al. (2025) recently repeated the idea with pigeons and compound stimuli, proving the rule still holds thirty years on.
Campbell (2003) pushed the ratio to extremes and saw kids start to ignore the sample—warning us that too-big pay gaps break the task.
Why it matters
When you set up matching-to-sample for stimulus equivalence, keep reinforcer rates close across choices. If one correct answer pays double, learners may pick it even when the sample says don’t. Check your token or praise schedule the way you check your stimuli—both control responding.
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02At a glance
03Original abstract
Four experiments, each with 6 human subjects, varied the distribution of reinforcers for correct responses and the probability of sample-stimulus presentation in symbolic matching-to-sample procedures. Experiment 1 held the sample-stimulus probability constant and varied the ratio of reinforcers obtained for correct responses on the two alternatives across conditions. There was a positive relation between measures of response bias and the ratio of reinforcers. Experiment 2 held the ratio of reinforcers constant and varied the sample-stimulus probability across conditions. Unlike previous studies that used pigeons as subjects, there was a negative relation between bias and the ratio of sample-stimulus presentations. In Experiment 3, the sample-stimulus probability and the reinforcer ratio covaried across conditions. Response bias did not vary systematically across conditions. In Experiments 1 to 3, correct responses were reinforced intermittently. Experiment 4 used the same procedure as Experiment 3, but all correct responses now produced some scheduled consequence. There was a positive relation between response bias and the ratio of reinforcers. The results suggest that human performance in these tasks was controlled by both the relative frequency of reinforced responses and the relative frequency of nonreinforced responses.
Journal of the experimental analysis of behavior, 1995 · doi:10.1901/jeab.1995.63-53