- In his paper '"General Intelligence," Objectively Determined and Measured,' Charles Spearman observed that people who did well on one mental task tended to do well on others.
- Spearman labeled this shared factor g, for general intelligence, the part of performance common to every cognitive task.
- To support his theory, Spearman helped develop factor analysis, a statistical method for finding hidden patterns behind many correlated measurements.
- The reality of a strong general factor in test data is widely replicated, and g predicts many real-world outcomes.
What did Spearman discover in 1904?
In his paper '"General Intelligence," Objectively Determined and Measured,' Charles Spearman observed that people who did well on one mental task tended to do well on others. He called this tendency for all abilities to correlate positively the positive manifold. To explain it, he proposed an underlying common factor.
What is the g factor?
Spearman labeled this shared factor g, for general intelligence, the part of performance common to every cognitive task. His two-factor theory held that each test reflects g plus an s factor specific to that task. The idea was that g acts like a general mental energy fueling all kinds of thinking.
What is factor analysis?
To support his theory, Spearman helped develop factor analysis, a statistical method for finding hidden patterns behind many correlated measurements. It reduces a tangle of test scores to a smaller set of underlying factors. The technique became one of psychology's most important and most debated tools.
Is the g factor still accepted?
The reality of a strong general factor in test data is widely replicated, and g predicts many real-world outcomes. But scholars disagree over what g actually is and whether it reflects one ability or many working together. Critics argue it may be a statistical artifact of how tests are built rather than a single thing in the brain.