Gilbert, DanielLevari, David Emmanuel2019-08-082018-052018-05-132018Levari, David Emmanuel. 2018. Prevalence-Induced Concept Change in Human Judgment. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.http://nrs.harvard.edu/urn-3:HUL.InstRepos:41127358Why do social problems seem so intractable? In a series of experiments, I show that people often respond to decreases in the prevalence of a stimulus by “expanding their concept” of it. When blue dots became rare, participants began to see purple dots as blue; when threatening faces became rare, participants began to see neutral faces as threatening; and when unethical requests became rare, participants began to see innocuous requests as unethical. This prevalence-induced concept change occurred even when participants were forewarned about it and even when they were instructed and paid to resist it. I then present a computational model suggesting that this phenomenon is driven by a range-frequency compromise in judgment. One reason social problems may seem so intractable is that a reduction in their prevalence can lead people to see more of them.application/pdfenprevalencethresholdsdetectioncontextual judgmentpsychologyconceptscreepcomputational modelsrange-frequency theorycolormoralityThesis or Dissertation2019-08-080000-0002-7953-7999