In the inspection-time task, a person looks at two vertical lines of unequal length and is asked to identify which of the two is longer. Inspection time is the length of time of stimulus presentation each individual needs in order to discriminate which of the two lines is the longest. Some research suggests that more-intelligent individuals are able to discriminate the lengths of the lines in shorter inspection times.

Robert J.Sternberg, Encyclopædia Britannica, Intelligence

This study replicated and extended Kranzler and Jensen’s [Intelligence 13 (1989) 329] meta-analysis of the relationship between inspection time (IT) and intelligence (IQ). […] meta-analyses were conducted on obtained correlations (r’s) between IT and general IQ. […] For the total sample (N>4100), the r was −.51 after correction for artifactual effects (−.30 prior to correction).

Jennifer L. Grudnik, John H. Kranzler, “Meta-analysis of the relationship between intelligence and inspection time”, Intelligence, Volume 29, Issue 6, November–December 2001, Pages 523-535,

Neuropsychologists and cognitive researchers often need quick estimates of global cognitive functioning [i.e., intelligence quotient (IQ)]. […]

The current article examined 11 proxy measures to determine their level of agreement with WAIS-III FSIQ across the entire sample. [(Wechsler Adult Intelligence Scale [Third Edition] full scale IQ test)] […]

Measures evaluated for this study included the Ward-7ST short form developed by Ward and modifi ed for the WAISIII by Pilgrim et al. ( 1999 ), the NAART, the SILS, ITBS, the Barona and Crawford demographic regression formulae, and the fi ve OPIE3 hybrids combining demographic and WAIS-III subtest information. The fi nal estimate examined was the ITBS (Hoover et al., 2003 ), a nationally recognized standardized school achievement test.

The Pearson correlation and confidence interval between WAIS-III FSIQ and each proxy measure are shown in Table 2 . Correlations ranged from r = .25 for the Barona estimate to r = .95 for the Ward-7ST short form.

The performance of the proxy measures across the different cognitive ability groups was examined next. […]

Above-Average IQ Group

[…] The Ward-7ST estimate was the only proxy to correlate above r = .70 for the high ability group. […]

The most important finding of this article is how poorly the IQ proxy measures performed at the tails of the IQ distribution. The proxy measures consistently overestimated the IQ of lowfunctioning individuals and underestimated the IQs of highfunctioning individuals.

Spinks, Mckirgan, Arndt, Caspers, Yucuis and Pfalzgraf (2009). IQ estimate smackdown: comparing IQ proxy measures to the WAIS-III. Journal of the International Neuropsychological Society. 15. 590-6. doi:10.1017/S1355617709090766.

Added to diary 27 June 2018