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Effect of Presenting Baseline Probes During or After Emergent Relations Tests on Equivalence Class Formation


The present experiment investigated whether the interspersion of baseline probes among emergent test trials would enhance the yields of equivalence class formation following the exposure to the One-to-Many (OTM) training structure. Twenty adults were exposed to two test protocols, in counterbalanced order: Simultaneous Protocol with Baseline Intermixed and Simultaneous Protocol with Posttest of Baseline (Conditions MixB and PTB, respectively). The conditions varied in respect to test procedure and stimuli set. Both started by training AB, AC, AD, and AE relations concurrently. Next, a test assessed the maintenance of baseline and the emergence of symmetry (BA, CA, DA, EA) and equivalence (BC, BD, BE, CB, CD, CE, DB, DC, DE, EB, EC, ED) relations. In Condition MixB, all test trials were presented concurrently. In Condition PTB, baseline probes were presented after symmetry and equivalence were assessed simultaneously. All participants formed equivalence classes in both conditions. Condition MixB presented slightly lower yields of immediate emergence (16 participants) than Condition PTB (18). Three out of the four participants with delayed emergence in Condition MixB initially failed in symmetry trials, the other two in Condition PTB failed exclusively in equivalence trials. Condition MixB produced significantly faster correct responses over the first five equivalence test trials. The results support that the OTM training structure is highly effective with normal adults, regardless of the interspersion of baseline probes in the test. Also, these results have implications for conclusions about the relevant variables for the OTM efficacy.

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The authors express sincere gratitude to Dr. Deisy G. de Souza and Dr. Julio C. C. de Rose for granting the facilities at the Federal University of São Carlos, Brazil, where the study was conducted.


This research was funded by Oslo Metropolitan University.

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Correspondence to Vanessa Ayres-Pereira.

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The authors declare that there is no conflict of interest.

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All procedures performed in studies involving human participants were in accordance with the ethical standards and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The Brazilian National Council on Human Research approved the procedures (CONEP; Protocol CAAE 59735416.2.0000.5504).

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Ayres-Pereira, V., Arntzen, E. Effect of Presenting Baseline Probes During or After Emergent Relations Tests on Equivalence Class Formation. Psychol Rec 69, 193–204 (2019). https://doi.org/10.1007/s40732-018-0326-8

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Key words

  • stimulus equivalence
  • training structures
  • baseline probes
  • adult participants