The Threshold Effect of Intelligence

Key Insight

Extraordinary intelligence, exemplified by Christopher Langan's IQ of 195 (compared to an average of 100 or Einstein's 150) and his remarkable early abilities like speaking at 6 months and self-teaching to read at 3, has historically been seen as a primary indicator of future success. Lewis Terman's lifelong study of 1,470 'Termites'—children with IQs averaging over 140—was founded on the belief that such high intellect guaranteed leadership and exceptional achievement, shaping modern views on 'gifted' programs and elite admissions.

However, research reveals that the correlation between IQ and real-world success holds true only up to a certain point. Beyond an IQ of approximately 120, additional IQ points do not translate into measurable advantages. For instance, a scientist with an IQ of 130 is as likely to win a Nobel Prize as one with an IQ of 180. This phenomenon is analogous to height in basketball: a player needs to be tall enough (e.g., 6 feet) to play professionally, but beyond that threshold, extra inches do not inherently confer superiority, as exemplified by Michael Jordan being 6 foot 6.

This 'threshold effect' explains why Nobel laureates in Medicine and Chemistry often graduate from a diverse range of institutions, including not only elite universities like Harvard but also schools like DePauw or City College of New York, indicating they are 'smart enough,' rather than having the absolute highest IQs. Terman's oversight in not recognizing this threshold led to his Termites achieving mostly ordinary careers, with no Nobel Prize winners among them. In fact, two future Nobel laureates, William Shockley and Luis Alvarez, were excluded from his study due to insufficient IQ scores, underscoring that intellect and achievement are not perfectly correlated.