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Structure-based dissociations provide agnostic evidence to the multiple-systems debate

Nature Reviews Psychology volume 4, page 66 (2025)Cite this article

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Minda and colleagues review the literature in favour of multiple-systems accounts of category learning (Minda, J. P., Roark, C. L., Kalra, P. & Cruz, A. Single and multiple systems in categorization and category learning. Nat. Rev. Psychol. 3, 536–551 (2024))1, and focus on the competition between verbal and implicit systems (COVIS) model2. Their Review provides a comprehensive and nuanced account of the evidence, and mostly focuses on experiments that report dissociations between learning in rule-based category structures (in which optimal categorization can be achieved using simple verbalizable rules) and information-integration structures (in which optimal learning requires participants to predecisionally combine information from two or more incommensurate stimulus dimensions). However, there is a substantial issue in the interpretation of these results that might undermine the authors’ conclusions.

The COVIS model hypothesizes that there are two learning systems: an ‘explicit system’ that implements verbalizable rule strategies using working memory and an ‘implicit system’ (or procedural system) that uses a strategy of combining stimulus features and associating them with a response2. Critically, the COVIS model predicts that participants sometimes switch learning systems. In rule-based conditions, participants start learning using the explicit system with its easily verbalizable rules, find that it results in high accuracy and continue using that system. By contrast, in information-integration conditions, participants start learning using the explicit system but discover that it does not result in optimal responding because the structure is difficult to verbalize and applying rules results in poor accuracy, which motivates a switch to the implicit system. Thus, the COVIS model predicts that in information-integration conditions, there is always a portion of the experiment in which participants use the nonoptimal explicit system. For a researcher to draw conclusions about the properties of the implicit and explicit systems from experimental data, they first need to determine which system the participant used during the experiment.

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References

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Authors and Affiliations

  1. Psychology, Bath Spa University, Bath, UK

    C. E. R. Edmunds

  2. School of Psychology, University of Plymouth, Plymouth, UK

    Andy J. Wills

  3. School of Psychology, University of Exeter, Exeter, UK

    Fraser Milton

Authors
  1. C. E. R. Edmunds
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  2. Andy J. Wills
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  3. Fraser Milton
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Correspondence to C. E. R. Edmunds.

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Edmunds, C.E.R., Wills, A.J. & Milton, F. Structure-based dissociations provide agnostic evidence to the multiple-systems debate. Nat Rev Psychol 4, 66 (2025). https://doi.org/10.1038/s44159-024-00395-w

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