A Rejoinder to Mackintosh and some Remarks on the Concept of General Intelligence

In 2000 Nicholas J. Mackintosh (2000) published an article in “Nature” referring to the concept of general intelligence (“g”) claiming that there is clear empirical evidence for the existence of the g factor and psychologists are “united in their support of g”. Surprisingly, his view remained yet unchallenged although this issue is by no means as clear-cut as Mackintosh argues. Let us therefore attempt to clarify some common but unfortunately major misconceptions about g, which Mackintosh, following Jensen’s (1998) precedent, recounted in his “Nature” article. The bottom line is that Spearman’s g does not exist, that this has been known and acknowledged by leading scholars (Guttman, 1992; Thurstone, 1947) of factor analysis for decades so that the task of objectively defining human intelligence remains unfinished.

💡 Research Summary

The paper presents a systematic rebuttal to Nicholas J. Mackintosh’s 2000 “Nature” article, which claimed that the general intelligence factor (g) enjoys clear empirical support and broad consensus among psychologists. The author begins by revisiting Charles Spearman’s original two‑factor model—general factor g and specific factors s—and demonstrates that contemporary data sets fail to replicate a stable, single‑factor structure. Citing Guttman (1992), the paper notes that a pure g model consistently falls short on standard fit indices such as chi‑square, RMSEA, and CFI, indicating that g is often an artefact of forced factor extraction rather than a genuine latent construct. The discussion then turns to L. L. Thurstone’s multi‑factor perspective, which has long argued that intelligence comprises several relatively independent primary mental abilities. Modern cognitive neuroscience and psychometric research continue to support this view, showing that brain‑behavior relationships are better explained by a network of abilities than by a single overarching factor.

The author further critiques Mackintosh’s reliance on Jensen (1998), pointing out that Jensen’s samples were heavily biased toward Western, highly educated populations and that his test batteries were limited primarily to traditional IQ measures. Consequently, the purported universality of g is questionable. Recent neuroimaging studies have produced mixed results regarding correlations between g and specific neural substrates, reinforcing the notion that intelligence is multidimensional. Moreover, the paper emphasizes that the psychological community has never reached a genuine consensus on g; instead, a plurality of models—multiple intelligences, working‑memory frameworks, executive‑function theories—coexist and often outperform single‑factor approaches in predictive validity.

In concluding, the author argues that Mackintosh’s confident narrative overlooks decades of methodological debate and empirical evidence that challenge the existence of a unitary g. The task of defining and measuring human intelligence remains unfinished, and future research should shift away from an exclusive focus on g toward integrative, multi‑factor models that capture the complex architecture of cognitive abilities. This shift, the author suggests, will provide a more accurate and scientifically robust understanding of human intellect.