Behavioral pharmacology and verbal behavior: Diazepam effects on verbal self-reports.
Diazepam can make clients sound sure they aced a task even when their actual performance slipped only a little.
01Research in Context
What this study did
Glenn (1993) gave one 10 mg diazepam pill to healthy adults. Each adult then did a matching-to-sample task and told the researcher how well they thought they did.
The team tracked real accuracy and the accuracy of the verbal self-report. They wanted to see if the drug changed how honest or accurate people were about their own work.
What they found
Diazepam barely hurt the actual matching scores. It did make people say "I did great!" far more often when they had not.
False success claims jumped, while real errors stayed small. The drug inflated confidence more than it hurt performance.
How this fits with other research
Bromley et al. (1998) warn that asking "Why did you do that?" can already twist verbal reports. Adding diazepam piles another layer of distortion on top.
Kohlenberg et al. (1976) used the same single-case lab style. They showed ethanol raised cigarette smoking, proving drugs can quietly shift operant behavior. Glenn (1993) shows the same for verbal behavior.
Perrin et al. (2021) and Pawlik et al. (2020) got clean data by collecting speech counts right during the task. Their method matches J et al.'s advice and helps you avoid the diazepam-type trap.
Why it matters
If your client takes benzodiazepines, do not trust glowing self-reports alone. Ask for live work samples, chart correct responses, and keep the session data visible. You will catch overconfidence before it hides real learning gaps.
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02At a glance
03Original abstract
Diazepam (10 mg) was administered to two men performing a delayed matching-to-sample task in which the number of elements in a compound sample stimulus (one of which appeared among 4 comparison stimuli) was manipulated from 1 to 3. After each trial, subjects pressed either a "Yes" or "No" button in response to a computer-presented query about whether the last choice met a point contingency requiring selection of the matching comparison stimulus within a time limit. Diazepam simultaneously produced marginal decreases in matching-to-sample performance and more pronounced decreases in the accuracy of self-reports about the same performance. Diazepam selectively increased false reports of success; false reports of failure were not systematically affected. A signal-detection analysis summarized these patterns as a decrease in self-report discriminability (A') with no systematic change in bias (B'(H)). These preliminary results converge with those of clinical lore and the results of studies with other benzodiazepine drugs in suggesting that diazepam can produce an "overconfidence" in performance self-evaluation, the mechanisms and parameters of which remain to be identified. The results were inconsistent with those of one previous study of diazepam's effects on performance self-evaluation, but given procedural differences between the two studies, the discrepancy may reflect the functional independence of verbal operant classes in Skinner's (1957) taxonomy.
The Analysis of verbal behavior, 1993 · doi:10.1007/BF03392886