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Intelligence and general cognitive function: the jangle fallacy

Molecular Psychiatry volume 28, pages 4490–4491 (2023)Cite this article

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The jangle fallacy is the assumption that two identical or highly similar things are different because they are named or labeled differently [1]. In their examination of factors associated with risk for Alzheimer’s disease (AD), the major conclusion of Hu et al. [2] is that “cognitive performance may protect against AD independently of intelligence” and that “intelligence may protect against AD dependently of cognitive performance”. Consideration of the jangle fallacy, however, demonstrates that this conclusion is not meaningful. The jangle fallacy here refers to the constructs of intelligence and cognitive performance. Hu et al. also refer to cognitive performance as general cognitive function, and we therefore use these two terms interchangeably.

In our view, Hu et al.’s conceptualization of intelligence and general cognitive function is problematic. It is that conceptualization that leads, in part, to the jangle fallacy, i.e., the erroneous assumption that these are distinct constructs. Hu et al. state that in addition to intelligence, “general cognitive function estimates the overall cognitive performance for a person, and is a prominent and relatively stable human phenotype compared with specific cognitive abilities, such as intelligence.” However, intelligence is not a specific cognitive ability; it represents general cognitive function. Indeed, in neuropsychology, intelligence/general cognitive function is always differentiated from specific cognitive abilities such as memory, executive function, or visual-spatial ability. Hu et al. also state that intelligence is “largely fixed early in life.” While correlational results suggest stability in adulthood, other results indicate that intelligence may not be so fixed across the lifespan. Stability of intelligence from early in life is rather hard to measure because the cognitive tests used to evaluate young children and adults usually need to be very different. One exception is the Lothian Birth Cohorts in which the same intelligence test was given to children at age 11 and then to the same individuals in their 70 s [3]. The correlation was 0.63 over this very long interval, but there was a mean score increase of 1.12–1.51 SDs [3]. In contrast, when considering intelligence from young adulthood to older adulthood, mean level change tends to be in the opposite direction. For example, the same Wechsler IQ is achieved with lower raw scores for a 75-year old compared with a 25-year old [4]. Thus, there is conceptual confusion in the basic arguments of the paper.

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References

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Acknowledgements

The author was supported by National Institute on Aging grants R01 AG050595, R01 AG076838, R01 AG060470, R01 AG064955, and P01 AG055367.

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  1. Department of Psychiatry and Center for Behavior Genetics of Aging, University of California, San Diego, La Jolla, CA, 92093, USA

    William S. Kremen, Matthew S. Panizzon & Carol E. Franz

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  1. William S. Kremen
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  3. Carol E. Franz
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WSK conceptualized and wrote the letter. MSP and CEF contributed critical comments and edits to the letter.

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Correspondence to William S. Kremen.

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Kremen, W.S., Panizzon, M.S. & Franz, C.E. Intelligence and general cognitive function: the jangle fallacy. Mol Psychiatry 28, 4490–4491 (2023). https://doi.org/10.1038/s41380-023-02058-3

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