 A 2015 study found that Olduvai copy number is linearly correlated with increased cognitive function, as measured by total IQ and mathematical aptitude scores, a finding replicated in two independent groups from different countries.The study specifically studied the Olduvai variants CON1 and CON2, noting that measurement of the very high copy number HLS1–3 variants had been challenging given technologies currently available.It found that those with a higher number of copies of CON2 had higher scores on the WISC IQ test and the Progressive Achievement Mathematics test.