Blank-comparison matching-to-sample reveals a false positive symmetry test in a capuchin monkey

UMMS Affiliation

Intellectual and Developmental Disabilities Research Center; Shriver Center

Publication Date


Document Type



Experimental Analysis of Behavior | Psychiatry and Psychology


A positive symmetry test result was obtained with a capuchin monkey that had previously exhibited virtually errorless AB and BA arbitrary matching-to-sample (MTS) with different stimuli. The symmetry test (BA) followed the acquisition of a new AB relation. It seemed possible, however, that the positive result could have occurred through the exclusion of previously defined comparison stimuli and not because the new AB and BA relations had the property of symmetry. To assess this possibility, a blank-comparison MTS procedure was implemented that permitted the separate assessment of select and reject (i.e., exclusion) control with both baseline and BA matching relations. In this assessment, the monkey did not exhibit reliable BA matching when exclusion was not possible, thus showing that the symmetry result was a false positive. However, the study demonstrated the feasibility of using a blank comparison MTS procedure with capuchins. The present results may set the stage for more successful methodology for establishing desired forms of relational stimulus control in capuchins and ultimately improving the assessment of relational learning capacity in that species, other nonhuman species, and nonverbal humans.

DOI of Published Version



de Faria Brino AL, da Silva Campos R, de Faria Galvão O, McIlvane WJ. Blank-comparison matching-to-sample reveals a false positive symmetry test in a capuchin monkey. Psychol Neurosci. 2014 Jun 1;7(2):193-198. PubMed PMID: 25383161; PubMed Central PMCID: PMC4219868. Link to article on publisher's site

Journal/Book/Conference Title

Psychology and neuroscience

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