Functional equivalence in pigeons involving a four-member class

Andrea M. Friedrich, Tricia S. Clement, Thomas R. Zentall

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Research suggests that animals are capable of forming functional equivalence relations or stimulus classes of the kind usually demonstrated by humans (e.g., the class defined by an object and the word for that object). In pigeons, such functional equivalences are typically established using many-to-one matching-to-sample in which two samples are associated with one comparison stimulus and two different samples are associated with the other. Evidence for the establishment of functional equivalences between samples associated with the same comparison comes from transfer tests. In Experiment 1, we found that pigeons can form a single class consisting of four members (many-to-one matching) when the alternative class has only one member (one-to-one matching). In Experiment 2, we ruled out the possibility that the pigeons acquired the hybrid one-to-one/many-to-one task by developing a single-code/default coding strategy as earlier research suggested that it might. Thus, pigeons can develop a functional class consisting of as many as four members, with the alternative class consisting of a single member.

Original languageEnglish
Pages (from-to)395-403
Number of pages9
JournalBehavioural Processes
Issue number3
StatePublished - Nov 30 2004

Bibliographical note

Funding Information:
This research was supported by National Institute of Mental Health Grant MH-59194.Correspondence concerning this article should be sent to T. R. Zentall, Department of Psychology, University of Kentucky, Lexington, KY 40506-0044 (email: ).


  • Functional equivalence
  • Many-to-one matching
  • Pigeons
  • Single-code/default
  • Stimulus class formation

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Behavioral Neuroscience


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