IQ Tests are ubiquitously understood to measure intelligence; they test one’s Intelligence Quotient after all. Contrary to this popular belief, however, Duckworth, Quinn, Lynam, Loeber, and Stouthamer-Loeber (2011) found that IQ tests also measure something else: one’s motivation during the test. It seems intuitive that one’s performance during a test could be benefited or retarded depending on factors secondary to their level of intelligence; for example, consider the IQ result of a high-achieving medical student who has been sleep deprived for 72 hours. Context of an IQ score matters. One factor that needs to be addressed is motivation — the degree of effort and concentration offered in attempt to succeed on an IQ test. Beyond extreme cases such as the one previously referenced, how much variability in IQ score performance can be attributed to differences in motivation, and how should this affect our interpretation of IQ tests.
Duckworth et al. addressed this. Overall, by adding an incentive for success, and hence raising one’s level of motivation, IQ scores increased by an average of 0.64 standard deviations; specifically, an incentive increased scores for below-average individuals by 0.94 SD and above-average achievers by 0.26 SD (2011). Moreover, they found that motivation during the test (measured objectively by an observer) was correlated to the same measures associated with intelligence, namely academic performance, among others (Duckworth et al., 2011). For example, the study concludes that the 40.1% correlation between academic performance and IQ score can be broken down into 31.0% level of intelligence and 9.2% level of motivation (Duckworth et al., 2011).
A consequence of these findings is that in situations where one is not particularly motivated, for example during a research study, a test for purely statistical/census reasons, or perhaps where one doesn’t understand how the test will be used, will likely produce an overall lower IQ than under other conditions. Consider an in-patient of a home for “mentally defective” persons during the Eugenics movement, who may not understand or be warned of the consequences of underperforming. Or an undergrad participating in a study for credit whose performance doesn’t affect his credit. Keep in mind this effect is magnified for lower performers.
In short, if a person isn’t cognizant of the consequences of the test, it may not be valid. Motivation is a variable that ultimately needs to be controlled, and which needs to be considered when assessing the results of an IQ test.
Duckworth, A. L., Quinn, P. D., Lynam, D. R., Loeber, R., & Stouthamer-Loeber, M. (2011, April 25). Role of test motivation in intelligence testing. Proceedings of the National Academy of Sciences of the United States of America, 108(19), 7716–7720.
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