Are IQ Tests Legal for Employment? Why the Ban Is a Myth

Are IQ tests legal for employment? Yes. IQ and other cognitive ability tests are legal in United States hiring. Title VII of the Civil Rights Act of 1964, as the Supreme Court read it in Griggs v. Duke Power (1971), bars a test that screens out a protected group unless the employer shows it is job related and consistent with business necessity. The EEOC's four-fifths rule flags a problem when one group's pass rate falls below 80% of the top group's. This is general information, not legal advice.

The ban people describe never happened. Below: what Griggs decided, a worked four-fifths example, an employer checklist taken from the federal rules, and what the Civil Rights Act of 1991 changed.

Ask around an HR department whether you can give job applicants an intelligence test and someone will tell you it is illegal in the United States. It is one of the most durable pieces of workplace folklore there is, it is repeated in good faith, and it is wrong. What the law did was attach a condition to the practice. The condition is demanding enough that many employers gave up rather than meet it, and over fifty years the giving-up got remembered as a ban.

This is an explanation of where the rule came from and what it says, not legal advice. Employment law is jurisdiction-specific and fact-specific, and anyone actually designing a selection process needs a lawyer rather than an article.

Why did they ban IQ testing in job applications?

Why did they ban IQ testing in job applications? They did not. The belief traces to one case, Griggs v. Duke Power Co., decided by the Supreme Court on 8 March 1971. It attached a condition to testing, not a ban, and the Chief Justice said so in plain words.

Duke Power required a high school education for most departments. From September 1965 it let employees without one qualify for transfer by passing two tests, the Wonderlic Personnel Test and the Bennett Mechanical Comprehension Test. The Court described the Wonderlic as a test that "purports to measure general intelligence". The cut scores approximated the national median for high school graduates. Neither test was directed or intended to measure the ability to learn a particular job, and both screened out Black applicants at a substantially higher rate.

The Court held that Title VII of the Civil Rights Act of 1964 reaches practices that are neutral on their face and neutral in intent, if they operate to exclude a protected group and cannot be shown to be related to job performance. Good faith is not a defence: what matters is the consequence of the practice, not the motive behind it. That doctrine is what employment lawyers mean by disparate impact.

The opinion was careful about testing specifically. It said in terms that nothing in the Act forbids the use of testing or measuring procedures — what the Act forbids is giving them controlling force when they have not been shown to measure the person for the job rather than the person in the abstract. That sentence is the whole difference between a condition and a ban, and it is the sentence that dropped out of the folklore.

There is a detail worth noting for anyone who follows this section. The two instruments Duke Power used were the Wonderlic Personnel Test and the Bennett Mechanical Comprehension Test. The Wonderlic is not a historical curiosity — it is still administered, and it is still routinely converted into an IQ-style figure by people who should not be converting it. We went through what a Wonderlic score can and cannot be translated into separately. If you are preparing for one, our Wonderlic practice test shows the format and the timing.

Are IQ tests legal for employment?

Are IQ tests legal for employment under the statute? Yes. Section 703(h) of Title VII, now 42 U.S.C. § 2000e-2(h), says it is not an unlawful employment practice to give and act on the results of a professionally developed ability test. The condition is that the test, its administration or the action taken on its results is not designed, intended or used to discriminate on grounds of race, color, religion, sex or national origin. Griggs read that clause to mean that tests must be job related.

The Civil Rights Act of 1991 wrote the burden into the statute. Under 42 U.S.C. § 2000e-2(k), a disparate impact claim succeeds if the employer uses a practice that causes a disparate impact and fails to show it is "job related for the position in question and consistent with business necessity". A claimant can also win by pointing to an alternative practice with less impact that the employer refuses to adopt.

The rules that grew out of it

Four years later, Albemarle Paper Co. v. Moody (1975) pressed on what "shown to be job-related" requires, and found the employer's validation evidence in that case inadequate. In 1978 the federal enforcement agencies issued the Uniform Guidelines on Employee Selection Procedures, codified at 29 CFR Part 1607, which remain the operational reference. The Guidelines set out two things worth knowing even if you never read them:

• A rule of thumb for spotting adverse impact, the four-fifths rule in 29 CFR 1607.4(D). A selection rate for any group that is less than four-fifths (80%) of the rate for the group with the highest rate will generally be regarded by the federal agencies as evidence of adverse impact. The Guidelines add that smaller differences can still count when they are significant in statistical and practical terms, and that larger ones may not count when the numbers are small
• Three recognised ways to show a selection procedure is valid (29 CFR 1607.5): criterion-related validity, evidence that scores predict or correlate with important elements of job performance; content validity, evidence that the test is representative of important aspects of the job; and construct validity, evidence that it measures a trait the job demonstrably needs

Here is the arithmetic. Say 50 of 100 applicants from one group pass a test (a 50% rate) and 30 of 100 from another group pass (30%). The second rate is 30 divided by 50, or 60% of the first. That is below 80%, so the agencies would generally treat it as evidence of adverse impact. If 40 had passed, the ratio would be 40 divided by 50, or exactly 80%, which is not below four-fifths. Our guide to the four-fifths rule works through more cases.

Adverse impact alone does not make a test unlawful. It shifts the burden. Once impact is shown, the employer has to produce evidence that the test is job related and consistent with business necessity, and a challenger can still argue that an equally effective alternative with less impact was available. Each step is evidentiary. It is a serious amount of work, and a small employer can reasonably decide that an off-the-shelf ability test is not worth the paperwork. That is a commercial decision, not a legal prohibition.

Is it illegal to IQ test employees? An employer checklist

Is it illegal to IQ test employees? Not under federal law, if the test is used lawfully. Are IQ tests illegal for employment, then? No, but they are regulated. For current employees as well as applicants, Title VII asks the same two questions: does the test screen out a protected group, and if so, is it job related? State and local rules may add limits, and we have not surveyed them. A checklist drawn from the federal rules:

• Start from the job. A validity study should show that scores are predictive of or significantly correlated with important elements of job performance (29 CFR 1607.5)
• Keep selection data by group for each job. Employers with 100 or fewer employees may keep simpler records of hires, promotions, applicants and procedures used (29 CFR 1607.15)
• Run the four-fifths check on the pass rates: the lowest group's rate divided by the highest group's rate. Below 0.80 is generally treated as evidence of adverse impact (29 CFR 1607.4(D))
• If there is adverse impact, validate the test by a criterion-related, content or construct study (29 CFR 1607.5)
• Look for an equally valid alternative with less adverse impact, and use it (29 CFR 1607.3(B); 42 U.S.C. § 2000e-2(k))
• Never adjust scores, set different cutoffs or otherwise alter test results by race, color, religion, sex or national origin (42 U.S.C. § 2000e-2(l))
• Use the score only for what it was validated for. A Wonderlic result is not an IQ, as our guide to Wonderlic score to IQ conversion explains
• Plan accommodations for candidates with disabilities, especially on timed tests, and document every decision

Why employers kept using them anyway

It would be a tidier story if employers had simply abandoned cognitive testing, and many did. Plenty did not, because general mental ability is among the most heavily studied predictors of job performance. A 2022 reanalysis by Sackett and colleagues in the Journal of Applied Psychology found that older validity estimates had been overstated. Mean validity estimates fell by .10 to .20 points, most procedures kept their rank, and structured interviews came out on top. The authors concluded that selection procedures remain useful, but that the relationships are considerably lower than previously thought.

So a test can add information, but it is no verdict. Prediction that holds on average across thousands of people is compatible with wide variation for any one person, and a process resting on a single number discards what a work sample or a structured interview would add. We set out what the relationship looks like in what a workplace test score predicts. Our study of which employers use aptitude tests shows who still relies on them.

The thing that is genuinely banned

There is one practice around cognitive testing that American law prohibits outright, and it is not the testing. Section 106 of the Civil Rights Act of 1991, now 42 U.S.C. § 2000e-2(l), made it unlawful, in connection with employment-related tests, to adjust scores, use different cutoffs, or otherwise alter results on the basis of race, color, religion, sex or national origin. The practice it was aimed at is usually called race-norming: reporting an applicant's standing within their own demographic group rather than against everybody.

The irony is worth sitting with. The provision most people half-remember as "IQ tests are illegal" is in fact the provision that requires everyone to be scored against the same table. Whatever you think of that as policy, it points in the opposite direction to the myth.

Outside the United States

The American framing does not travel. In the United Kingdom, the Equality Act 2010 handles the same problem through indirect discrimination: a provision applied to everyone that puts people sharing a protected characteristic at a particular disadvantage is unlawful unless the employer can show it is a proportionate means of achieving a legitimate aim. The vocabulary is different; the underlying demand — justify it against the job — is recognisably the same.

Across the European Union the pressure has shifted onto the automation around the test rather than the test itself. The General Data Protection Regulation constrains decisions taken solely by automated processing where they produce legal or similarly significant effects, and the EU AI Act treats systems used in recruitment and selection as high-risk, with obligations that phase in over several years. Our piece on what the AI Act means for hiring assessments follows that timetable. A scored aptitude test that a human then interprets sits in a different place from an automated ranking that nobody reviews, and that distinction is doing most of the work.

What this means if you are the one being tested

• A cognitive test in a hiring process is, in most jurisdictions, lawful. If it screens out a protected group at a materially different rate, the employer needs evidence it is about the job.
• Ask what the test is and what the score is used for. A reputable process can tell you the instrument, whether the score is a cutoff or one input among several, and whether it is combined with anything else.
• A score is not a verdict. Cognitive ability tests predict job performance on average across many people, with wide spread around that average for any individual — we set out what the relationship actually looks like in what a workplace test score predicts.
• Practice effects are real and they are not cheating. Second scores on the same or similar tests run higher for reasons that have nothing to do with ability, which is a measurement problem for the employer rather than a moral one for you.
• If you need an accommodation, ask early. Timed tests are the common flashpoint and the request is routine.

If a number has already been handed to you, the first useful move is arithmetic rather than argument: establish which instrument produced it and what standard deviation that instrument uses, then convert it. Our percentile calculator turns a score into a rank once you supply the scale, and the score converter moves a figure between the common scales so that two results from two employers can be compared at all. For a test that covers several abilities, see our aptitude test. If you want a baseline of your own, our IQ test reports the scale, the percentile and the confidence range together, which is the format an employer-supplied figure should arrive in too.

If you run hiring for a company and want assessments with documented scoring, see our business page.

The useful correction is small. The rule was never "you may not test". It was "you may not use a test you cannot connect to the job", which is a defensible thing to ask of anyone making a hiring decision, and which sounds a great deal less dramatic than a ban. Fifty years of retelling turned a condition into a prohibition, and the prohibition is now quoted more often than the case. That is worth remembering the next time a workplace claim arrives with no citation attached. The McKinsey Solve pages show what a published employer position looks like, and what it leaves out; see McKinsey Solve: is it an IQ test.

Common questions