The Validity of IQ Tests in the Presence of Practice and Coaching

Imagine you are preparing for an IQ test as an adult. You may have noticed that your preparation can significantly affect your score. But does this mean that practice and coaching automatically invalidate an IQ test?

Contextualizing Practice and Coaching

Let's consider a scenario where you hardly ever read and thus miss questions on an IQ test that require understanding words like “vicissitudes”. After reading a couple of definitional books, you take the test again and achieve a better score. This begs the question: which score more accurately reflects your true intelligence?

Suppose you are asked to draw a realistic picture of a horse. If you practice drawing horses for two weeks, it is clear that your performance will improve significantly. Would this practice prove that your superior performance reflects true intellect or the ability to improve with practice and coaching? This raises a critical point: would practice or coaching disqualify an IQ test as a measure of intelligence?

IQ Tests and the Measurement of Intelligence

IQ tests aim to measure multiple aspects of intelligence, including the general factor Spearman’s g, non-g group factors, uniqueness, and specific factors.

The General Factor (g)

Spearman’s g is often considered the essence of intelligence. It represents the general cognitive ability that can be measured by IQ tests. However, non-g group factors can also be present, reflecting broad ability residuals after g is factored out.

Specific Factors and Random Error

Specific factors and random error contribute to the variance of test scores. When you study and learn specific test items, the specificity of your knowledge increases, which can lower the g loading of those items. This means that the test's validity is reduced since the sum of the variances must always equal 100.

The Impact of Practice and Coaching on Test Validity

When you study for an IQ test, the extent to which you can improve your score often depends on the number of items you can master and the gain in correctly responding to those items. Any such training or study-related gains are indeed relevant, but they do not necessarily reflect an increase in actual intelligence.

The Conservation of G

Everyday life requires us to adapt and learn tasks, which can lead to the conservation of g. This means that as we learn, we rely less on our general intelligence (g) to perform tasks. However, this does not mean that our overall intelligence decreases; rather, we have become more specialized in certain areas.

Quantifying the Impact of Practice

The impact of practice on an IQ test's validity is similar to the difference in test validity between two tests with different g loadings. While the test's merits may be somewhat diminished, they are not entirely nullified.

Conclusion

In conclusion, practice and coaching do affect the score of an IQ test but do not necessarily invalidate it as a measure of true intelligence. The degree of impact depends on the extent of learning and the number of test items mastered. Understanding the nature of IQ tests and the role of Spearman’s g and specific factors helps in interpreting the results accurately.