Intelligence tests are designed to measure mental capacity, function and intellectual skills such as reasoning and understanding. For years, intelligence test results have been used in diagnoses, to make decisions about educational placement and to quantify how "smart" someone is. However, even when valid and reliable cognitive tests are administered by clinically trained professionals, there are drawbacks to testing intelligence in this way.

Limited Measurement

Intelligence tests measure specific thinking skills, such as reasoning and comprehension. However, intelligence consists of multiple skills and ways of thinking that are affected by genetics, environment, opportunities and experiences. Misconceptions that intelligence tests determine whether or not someone is "smart" lead to too much emphasis on one score that does not include every aspect of intelligence. Different elements of intelligence depend on the test taker's situation, and one test cannot cover every possible situation. Even tests with verified reliability and validity only measure a limited number of thinking skills.

Measure of Experience, Not Biology

Intelligence tests feature questions about concepts and objects based on context. Just because someone might not give the "correct" answer because the question is about something unfamiliar does not mean she isn't intelligent. For example, if an inner city student and a rural student both take the same test, and it has a question about a farm animal, missing the question because it is about something unfamiliar does not make the inner city student any less intelligent.

Intelligence tests measure how students respond to their environments; it doesn't measure their genetic predispositions. While genes will play some part in how students respond to what goes on around them, intelligence tests cannot measure their biological makeup or their true potential for being "smart." Therefore, they are inaccurate measures of true ability.

Biased Norms

Intelligence tests are normed on students with relatively privileged backgrounds and experiences, and this creates a bias in scoring. These norms put students from higher income families at an advantage over students from lower income families, because the advantaged students have more access to resources and enriching experiences.

Scores on IQ tests are affected by date of birth and how early students begin attending school. Students who begin school when they're older -- because they were born later in the year and are held back by age restrictions -- will be at a disadvantage. These variables are not accounted for in test norms.

Inaccurate Placement

While students are no longer diagnosed with learning disorders based on discrepancies between achievement and IQ scores, students are still often labeled and placed in classes based on intelligence assessments. Because a student's score does not truly reflect his abilities, however, placing him in a less challenging educational environment can prevent him from getting the knowledge or skills that would raise that score. For example, a low-income student with limited experiences may have a low IQ score because he is not familiar with some of the concepts presented in the questions. This can become a vicious cycle: Students who have more resources have more access to opportunities, while students who lack resources miss out on these opportunities. Students with better opportunities score higher and thus have access to more resources.