By Alex Fradera

Intelligence is a concept that some people have a hard time buying. It’s too multifaceted, too context-dependent, too Western. The US psychologist Edwin Boring encapsulated this scepticism when he said “measurable intelligence is simply what the tests of intelligence test.” Yet the scientific credentials of the concept are undimmed, partly because intelligence is strongly associated with so many important outcomes in life. Now Utah Valley University researchers Russell Warne and Cassidy Burningham have released evidence that further strengthens the case for intelligence being a valid and useful concept. Their PsyArXiv pre-print presents a cross-study analysis suggesting a single intelligence-like factor underpins mental performance across a wide range of non-western cultures.

Thanks to work pioneered by Charles Spearman, we know that in Western populations performance on a range of mental tasks seems to reflect a more basic mental ability, a “general intelligence” or simply g.

You can’t see g – it’s a statistical reality more than anything else, but it’s very robust, and modern research suggests that the g factor accounts for roughly half the variability in performance within and between people on all kinds of mental tests. Being strong verbally doesn’t guarantee you will be mathematical too, but it tips the odds strongly in your favour.

But it’s conceivable that g is not culturally universal – after all, there are many countries, especially non-Western, where relatively greater value is placed on the social and emotional aspects of intelligent behaviour (and where these non-cognitive skills are more closely tied to a successful life) – for instance, in Zimbabwe it is considered socially intelligent to prioritise caring for your relatives over friends or strangers. Also, people from different cultures performing the same task will often tackle it in a different way: past research found that Zambian children struggled in a traditional expression task using pen and paper, but were talented clay-moulders, for example. Could these cultural variations in behaviour and in the conception of what is considered smart reflect fundamental differences in how minds work?

To find out, Warne and Burningham searched the literature to find mental ability studies in non-industrialised, non-Western cultures (defined as less than half the population being White or European). They selected datasets that included participant results on four or more cognitive tasks so that it was possible to perform a “factor analysis” to identify how many factors seemed to be driving variation in performance across the different tests. Mostly there were standard intelligence measures, but also other types of test, including Piagetian development tasks, and tests designed to be specific to the cultural conditions, such as children’s willingness to interact with unfamiliar toys after seeing them used.

The analysis covered nearly 100 datasets from 31 cultures including Thailand, Uganda, Papau New Guinea, Guyana – from every inhabited continent and world region save Europe and Australia. The median sample size was 150, but due to some very large samples Warne and Burningham were working with 50,000 participants in all. They wanted to explore which cultures and which sets of tasks featured performance variation that could be reduced down to one factor akin to g, and which would firmly resist.

There are many ways to do factor analysis, especially around the decision rule of when to stop generating underlying factors, and this choice obviously influences the results that follow. Warne and Burningham argue that they chose rules that are deemed the most accurate in these sorts of circumstances, and they ran the analysis with two versions of the decision rule for safety, but it’s worth noting that others may disagree and to remember that this study is a pre-print so it has not yet been subjected to peer review.

Using Warne and Burningham’s rules, between three quarters and four-fifths of the datasets immediately yielded just one factor that explained variability in participants’ performance across different tests. In other cases, two underlying factors emerged, but these were similar enough to also end up reducing to one factor in a second round of analysis, saving one single exception.

Now, reducing variation in test performance to a general factor in dataset after dataset doesn’t mean that it must be the same general factor for all datasets, but it’s an obvious explanation. More so when you note that, on average, the first factor extracted explained almost half of the variance in performance across different tests – very similar to the g research in Western samples. Warne and Burningham state they “are astonished at the uniformity of these results” – given the wide variety of sample sizes, test content, and cultural locations.

This adds more evidence for g, which we know from previous research correlates with brain size, white matter tract integrity, genetic markers, and also seems to explain mental performance differences in other mammals, from primates to mice. The authors close by doubting whether we will ever solve the disagreement about what the culturally loaded term “intelligence” means worldwide. But we can still do the work to identify properties of the mind that are common to us all, and shape our ability to act in the world.

—Spearman’s g Found in 31 Non-Western Nations: Strong Evidence that g is a Universal Phenomenon [this paper is a pre-print meaning that it has not yet been subjected to peer review]

Alex Fradera (@alexfradera) is Staff Writer at BPS Research Digest