The Universal Law of Generalization Holds for Naturalistic Stimuli

Raja Marjieh, Nori Jacoby, Joshua C. Peterson, Thomas L. Griffiths

Research output: Contribution to journalArticlepeer-review


Shepard’s universal law of generalization is a remarkable hypothesis about how intelligent organisms should perceive similarity. In its broadest form, the universal law states that the level of perceived similarity between a pair of stimuli should decay as a concave function of their distance when embedded in an appropriate psychological space. While extensively studied, evidence in support of the universal law has relied on low-dimensional stimuli and small stimulus sets that are very different from their real-world counterparts. This is largely because pairwise comparisons—as required for similarity judgments—scale quadratically in the number of stimuli.We provide strong evidence for the universal law in a naturalistic high-dimensional regime by analyzing an existing data set of 214,200 human similarity judgments and a newly collected data set of 390,819 human generalization judgments (N = 2,406 U.S. participants) across three sets of natural images.

Original languageEnglish (US)
Pages (from-to)573-589
Number of pages17
JournalJournal of Experimental Psychology: General
Issue number3
StatePublished - 2024

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • General Psychology
  • Developmental Neuroscience


  • generalization
  • natural images
  • perception
  • representations
  • similarity


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