The Eysenck IQ test, read from its own pages: what the 1962 book and online quiz each document

0 The short answer

The Eysenck IQ test is not one instrument but a name shared by a family of Penguin books by Hans Eysenck that began with Know Your Own IQ in 1962 and by separate online quizzes that say they are based on his work, and none of the pages we could open publishes a norm group, a reliability figure or a validity study for the score. The book's own conversion tables were not available to us, so this page does not state them. The online quiz we read, which has 50 items and a 30 minute timer, says its result "summarizes your performance on this particular set of items." Read either as a self check on that set of items, and not as an IQ that can be compared with a score from a battery whose norms are documented.

1 What does "Eysenck IQ test" mean, and which version are you looking at?

Three different things answer to the name, and the first job of any honest answer is to say which one is meant: the original book, its later siblings, or an online quiz. The original is Know Your Own IQ, a Pelican paperback that Penguin's own catalogue says was first published in 1962. The siblings are the later titles under Hans Eysenck's name that library catalogues list, from Check Your Own IQ onward. The third is an online quiz, published by a website and not by Eysenck, that describes itself as based on his work. A search for "Eysenck IQ test" mixes the three, and so does most of what is written about them.

The distinction matters for a practical reason. A score is only as meaningful as the evidence for the specific test that produced it, and the three products share a name without sharing authors, items, dates or documentation. A reader who took the 1962 book, a reader who took the sequel and a reader who took the online quiz this week have taken three different instruments. Hans Eysenck, according to Penguin's page, lived from 1916 to 1997, so he cannot have written a quiz published by a website that says it was established in 2009, and the quiz does not claim he did. What it claims is that it is "based on the work of the seminal psychologist and IQ researcher Hans Jürgen Eysenck."

The question this page answers is narrower than "is the Eysenck IQ test good." It is what each version documents about itself, which of those documents bears on the number a reader receives, and what a reader can fairly say about a score from either. Hans Eysenck's wider research, including his work on personality, is outside the scope, except where it bears on how these tests should be read. The page on what IQ actually measures covers the construct, and the page on the history of IQ testing places a mid century popular test book in its period.

2 What is Know Your Own IQ, and what do the publisher and the catalogues say about it?

Know Your Own IQ is a self scoring paperback of timed intelligence tests for general readers, first published by Penguin in 1962, and the public record of it is thin on the one thing a score depends on, which is the norm. Penguin's catalogue page, read on October 20, 2026, lists the title as a Penguin Books paperback with ISBN 9781405932301, 192 pages, dated April 20, 2017, and priced at 9.99 pounds on the day read. It names Hans Eysenck (1916 to 1997) as the author.

The publisher's description makes four statements. The book was first published in 1962. It "was the first that permitted readers to determine their own I.Q." It opens with an introduction by Eysenck that explains what an IQ is and how it can be applied. And it then offers a range of "easy to difficult" challenges, with the answers and a personal IQ rating at the back. The Internet Archive's record of the 2017 edition carries the same description and the note "Originally published: 1962."

An older witness agrees on the date. The Wellcome Collection's catalogue entry for the Pelican edition gives Penguin Books, Harmondsworth, Middlesex, dated [1962] in square brackets, 190 pages with illustrations, in the Pelican Books series, under the subject heading Intelligence Tests. The date is given in square brackets, and the publisher's own statement supports it.

How widely it was read is recorded in a 1990 review. Raymond Fancher's review of Eysenck's autobiography in the London Review of Books says his lighter titles, including Know Your Own IQ, sold in the millions. That is a statement about circulation, not quality, and it is the best evidence on record that many people formed an idea of their own IQ from this book.

What the publisher's page does not say is as informative. It does not give the number of tests or items, the time limits, the age range the tables cover, the size or composition of any group the tests were tried on, the date of that trial, or how a raw score turns into the "personal I.Q. rating." The existence of a rating at the back implies a conversion table of some kind, but the page does not describe it, and we did not read it. The absence of a description in a sales page is not proof that the book contains no description, since an introduction that explains "what an IQ is" may well discuss standardization. It does mean that no reader can check the claim from the public record alone, and that anyone who quotes "the Eysenck norms" without holding the physical edition is quoting from memory or from a website.

A reader holding the book can settle the question in minutes by looking in the introduction and the back matter for a statement of who the tests were tried on, when, how many people, and what average and spread the scale uses. The checklist in a later section turns that into six questions.

3 Which other Eysenck IQ books exist, and which one does a search mean?

Library catalogues list many Eysenck records on IQ testing, in several languages and under several publishers, so "the Eysenck IQ test" can mean any of several books with different dates. Open Library's catalogue search for the author and the word IQ, run on October 20, 2026, returned 17 records. They include Know Your Own I.Q. under several publishers and years, Check Your Own I.Q. under several imprints, Test Your IQ (1994), Know Your Child's IQ, a Dutch De Eysenck IQ-test, a German children's IQ test book from Ullstein and an omnibus volume that combines the first two titles. They also include The IQ Argument: Race, Intelligence, and Education (1971), a different kind of book, which is a discussion of group differences and not a set of tests to take.

The sequel is the one most readers meet next. Check Your Own I.Q. is held by the Internet Archive as a Pelican Book (series number A656) published at Harmondsworth by Penguin, dated 1966 and marked as a reprint. The Open Library listing is less tidy: it carries one Check Your Own I.Q. record dated 1962 and another dated 1966, and the ISBN printed on the 1962 record matches the Pelican record the archive dates to 1966. Catalogues are compiled by cataloguers and merged by software, so first publication years on aggregators should be treated as leads, not facts. We use 1966 for the sequel because the archive's record of the physical Pelican copy carries it, and we do not claim more than that.

The later titles show how the product evolved. The Internet Archive lists Test Your IQ (Thorsons, London and San Francisco, 1994, 213 pages) and Test Your Child's Abilities: IQ Tests for Children Aged 10 to 15 (Thorsons, 1996, 233 pages), and the Open Library listing adds Know Your Child's IQ (Penguin, 1998 on the archive's record). The children's titles are outside this page, which is written for readers aged 16 and over, and any score in them would be read against a different age group.

Edition matters for a reason the Standards for Educational and Psychological Testing state directly. Standard 5.11 says that if a publisher provides norms, it is the publisher's responsibility, as long as the test stays in print, to renorm the test "with sufficient frequency" to permit continued accurate score interpretations. A paperback reissued in 2017 as a "classic" that "was first published in 1962" is in print. Whether the 2017 text was renormed, or reprints the 1962 tables, is not stated on the pages we could open, and it changes what any score in it means. The practical rule is to record which edition you hold, with its ISBN and the date on the copyright page, before attaching any meaning to a rating.

4 What does the online Eysenck IQ test say about itself?

The online quiz that carries Eysenck's name is a free, timed, 50 item test whose own page says it is based on his work and that it cannot replace a professional assessment, and the page we read reports no norm group, reliability or validity figures. We read the test page at idrlabs.com/eysenck-iq/test.php on October 20, 2026. The site that publishes it, IDRlabs, says on that page that it was established in 2009. This is the quiz that the older address, celebritytypes.com/eysenck-iq/test.php, redirected to when we opened it, so the two addresses lead to one test.

The page's own statements are specific enough to list. The test shows items one at a time, with a counter that reads "Question 1 of 50." It is in "timed mode," and the page says the reader has 30 minutes to finish after pressing start. Each item is displayed as an image, with numbered answer options and next and back buttons. The page says the test "is delivered to you free of charge." Its description of its origin is that it is "based on the work of the seminal psychologist and IQ researcher Hans Jürgen Eysenck." It then summarizes his research on the heritability of IQ, on whether IQ is stable across a lifetime, and on fluid and crystallized intelligence, and it adds that some of his theories and methods have faced criticism.

On accuracy the page is more guarded than a reader skimming a search result might expect. Its frequently asked questions say the result "summarizes your performance on this particular set of items," that an online score cannot replace a standardized, professionally administered assessment, and that one test cannot capture every aspect of intelligence. The disclaimer says free online quizzes like it "do not provide professional assessments or recommendations of any kind." Elsewhere the page says that statistical analysis is conducted "to ensure maximum accuracy and validity," and that it was made with input from people who work professionally in psychology.

Three things are absent from the text we read. The page does not give a norm group: no sample size, ages, country, year or method of recruitment. It does not report a reliability coefficient or any validity study. And it does not say how the items relate to Eysenck's published tests, whether they are drawn from them, modeled on them or merely inspired by his theories. Because we read the page and did not complete the test, we cannot say what the result screen shows, how the 50 responses become a number, or whether anything is offered for sale afterward. A reader who takes the quiz should look for those answers in the result itself, and the questions in the sections below are the ones to ask.

The honest summary is that the quiz is a free, timed set of 50 items with a clear disclaimer, offered under a famous name. That is a reasonable thing for a website to publish. What the evidence on its page does not support is a reading of the result as "an Eysenck IQ" in any sense that would let a person compare it with a school report, a clinician's assessment or a high IQ society's requirement. The page on free versus validated IQ tests sets out the general criteria, and the page on whether online IQ tests are accurate applies them to the category.

5 What is a norm, and what would a 1962 book have needed to document?

An IQ number is a position within a reference group, so a test that prints no description of its reference group has told you the number but not what it is a position in. A raw score, the count of items solved, means nothing by itself. It becomes an IQ only when it is converted through a table built from a sample of people who took the same test, and the conversion places a person at a point in that sample's distribution. On the modern convention the average is set at 100 and the standard deviation at 15, as the pages on the standard deviation of 15 and on how IQ scores are normed explain. Change the sample and the same raw score earns a different number.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014), published jointly by the American Educational Research Association, the American Psychological Association and the National Council on Measurement in Education, spell out what documentation a norm needs. We read the 2014 edition in the open access file on testingstandards.net. Standard 5.8 says norms, if used, should refer to clearly described populations that include the people with whom users will ordinarily want to compare their examinees. Standard 5.9 says reports of norming studies should specify the population sampled, the sampling procedures and participation rates, any weighting, and the dates of testing. Standard 5.2 adds that when a publisher supplies scales or norms, the technical documentation should describe the rationale and let users judge the quality and precision of the resulting scores.

Held against that list, a mid century popular book had a hard task. A trial with a few hundred readers or students is possible, a nationally representative sample of adults was expensive, and a book sold to the public for self scoring has no examiner to guarantee that the conditions of the trial were repeated by the buyer. We do not know which of these applies to Know Your Own IQ, because the publisher's page is silent and we did not read the physical book. It would be wrong to assume the worst, and equally wrong to assume a rigorous standardization from the author's reputation. A reputation is not a norm table.

For the online quiz the same standards apply with one difference: it is a modern product that could document its norms in a paragraph, and the page we read does not. The sentence "Statistical analysis of the test is conducted to ensure maximum accuracy and validity of the test scores" tells the reader that analysis occurs, but not what sample it used, what was found, or what value any coefficient took. By the criteria in Standard 5.9, that is a claim of validation without the report that would let a user judge it.

A reader holding either product can run a five line check, built from those standards. Who was in the sample, and how were they recruited? When was the sample tested? How many people, of what ages and in which country? What average and spread does the published scale assume? And what is the margin of error around a single result? If the answers are not printed, the number is best read as a private ranking of your own performance on that set of items, and it cannot be placed on the scale that a school, a clinician or a society uses. The page on reliability and validity explains the last two ideas in plain terms.

6 Why can a score tied to 1962 norms not be read as a score today?

Average performance on IQ tests has risen over the twentieth century, so a scale pegged to people tested in 1962 would place a modern test taker higher than a scale pegged to people tested recently, and the size of the shift is large enough to matter. This is the Flynn effect, named for the researcher whose 1984 paper in Psychological Bulletin, The mean IQ of Americans: Massive gains 1932 to 1978, put it on the record. The page on the Flynn effect covers the research; here we need only the size of the drift.

Two meta-analyses give figures. Pietschnig and Voracek's One Century of Global IQ Gains (Perspectives on Psychological Science, 2015) pooled 271 independent samples, almost 4 million participants and 31 countries from 1909 to 2013. They estimate gains of 0.41, 0.30, 0.28 and 0.21 IQ points a year for fluid, spatial, full scale and crystallized test performance respectively, with gains stronger for adults than children and decreasing in more recent decades. Trahan, Stuebing, Fletcher and Hiscock's meta-analysis (Psychological Bulletin, 2014) pooled 285 studies with 14,031 participants and found a mean of 2.31 standard score points per decade, and 2.93 points per decade for modern Stanford-Binet and Wechsler tests, which they describe as comparable to earlier estimates of about 3 points per decade. Their abstract describes the rise as resulting in norms obsolescence.

The table below applies those rates to the 64 years between 1962 and 2026. The last column is our arithmetic on published figures, shown only to give an order of magnitude. It is not a correction anyone can subtract from a score.

Three cautions keep that table honest. The rates are averages across many tests, countries and periods, and Pietschnig and Voracek report that gains decreased in recent decades, so a straight multiplication overstates the drift for the most recent years and understates it for earlier ones. The effect differs by ability, as the first three rows show. And the table applies only if a given score was calculated from a 1962 table. Whether any edition of the book was renormed, we cannot say. The only conclusion the numbers support is that an unrevised 1962 scale and a revised modern one would not agree, and the gap could be a decade of IQ points or more.

The Standards reach the same point from another side. The comment to Standard 5.3 warns that a score point originally defined as the mean of a reference population should no longer be read as average performance if the scale is held constant over time and the examinee population changes. Standard 5.11, quoted above, puts the duty to renorm on the publisher and the duty to avoid out of date norms on the user. The comparison has a familiar modern form: the page on why scores drop from the WAIS-IV to the WAIS-5 shows a revision with fresh norms producing lower numbers for the same people.

The consequence for a reader is concrete. If a person took a 1962 style test with its original conversion table today and received 130, the number would not mean that they sit at the 98th percentile of 2026 adults. It would mean they did well relative to people tested in the early 1960s, whose average on the same items was lower. The page on IQ percentiles shows what a given score means on a current scale, and the page on how rare a given IQ is turns it into one in a number.

7 What changes when you take the test at home, with an answer key or a timer?

Taking a test book or a browser quiz alone removes the conditions under which norms are collected, and the Standards treat the loss of those conditions as something a score report should disclose. A normed test is administered under standard conditions: a quiet room, fixed instructions, an exact time limit and someone who ensures that the person works alone. The Standards say, in their discussion of test administration, that testing conditions should in general be equivalent to those that prevailed when norms were obtained, and that for unmonitored settings such as the Internet the conditions of standardization should still be met or the report on the scores should note that standardized conditions were not guaranteed. We read both passages in Chapter 6 of the 2014 edition.

For the book, the publisher's description gives the structure: challenges from easy to difficult, with the answers and the rating "at the back of the book." That is a self scoring design, and it makes three problems unavoidable. The reader can see the answers before or during the test, however well meaning. The reader sets the clock, and a timed test run with a kitchen timer is a different test from one run by an examiner. And a book with many tests invites repeated attempts. The Standards also address integrity: Standard 6.6 asks for reasonable efforts to eliminate opportunities to obtain scores by fraudulent or deceptive means, which a printed answer key cannot do. This is not an accusation of readers. It is a description of what the format cannot control.

Practice is the most measurable of the three. Hausknecht, Halpert, Di Paolo and Moriarty Gerrard's meta-analysis of retesting (Journal of Applied Psychology, 2007) summarized 50 studies of practice effects on cognitive ability tests, with 107 samples and 134,436 participants. The adjusted overall effect size was .26, larger when practice came with coaching and larger when identical forms were used. If that effect size is read, as it usually is, as a standardized difference, it is roughly a quarter of a standard deviation, which on a scale with a standard deviation of 15 is about four points. That conversion is our arithmetic and not the authors' statement. The page on how to prepare for an IQ test covers what helps and what does not.

For the online quiz, the clock is software, not a person, and the page says "timed mode" with 30 minutes. A timer matters because speed is part of what the score measures. The Standards' glossary defines speededness as the extent to which scores depend on the rate at which work is performed as well as on the correctness of responses. A test with a short limit therefore rewards fast responding as well as reasoning, and an unsupervised browser cannot tell whether the limit was kept, whether a second device was open, or whether the person had seen the items. The page on why IQ tests are timed explains what the clock measures.

None of this proves a particular book or quiz is wrong. It shows that a result from either was produced under conditions that the norms, if any exist, were probably not produced under, and that the Standards would require a report on such a result to say so. The online quiz does say so, in its own way: its FAQ states that an online score cannot replace a standardized, professionally administered assessment. That sentence is the most accurate one on the page.

8 Which score can each version of the Eysenck IQ test support?

A fair reading ranks the four things a reader might hold by the documentation each publishes, and on the pages we could open none of the Eysenck versions reaches the level that would let its number stand in for a normed IQ. The table lists what the public pages document and what we could not find, with the date the pages were read. The right hand column states the sentence a reader could honestly say about a result.

Two points follow from the table. First, the question "which Eysenck test is most accurate" has no answer on the public record, because accuracy depends on documents the public record lacks. A reader who sees a website rank the book against the quiz on accuracy is looking at an opinion. Second, the statements in the right hand column are not insults. They are the ordinary scope of a self check: you did well or less well on a set of puzzles, relative to nobody in particular, and you can compare your own results across attempts if you control for practice.

The line to avoid is the jump from "I scored 135 on an Eysenck test" to "my IQ is 135." The second sentence uses the word IQ in the sense of a normed score, with a reference group and an error band. The first does not earn it unless the specific edition of the specific test prints those. The page on what a score means describes what the second sentence requires.

9 How do Eysenck's reputation and the later controversies bear on these tests?

Eysenck's fame explains why the name sells books and quizzes, but neither his reputation nor the later disputes about his research settles what any one test documents, and the evidence we found does not link the two. Hans Eysenck was a widely read public psychologist. The 1990 London Review of Books review quoted above says his popular books, among them Know Your Own IQ, sold in the millions, and its discussion of his intelligence work concerns his hereditarian views. The online quiz's page also says he argued that intelligence has a strong genetic component, supported by twin and family studies, and that some of his theories and methods have faced criticism. The page on heritability and what it actually means explains the concept at issue, and the page on whether IQ tests are biased covers a separate question about measurement.

A different matter is King's College London's statement on Hans Eysenck, read on October 20, 2026. It says King's conducted an enquiry in May 2019 into publications by Eysenck and Ronald Grossarth-Maticek, covering articles in peer reviewed journals where they appeared together and that analyzed data on personality and physical health outcomes. The published results of studies analyzing intervention or observational data were found to be unsafe. In an update dated October 6, 2025, King's said that, after concerns raised by Professor Anthony Pelosi about sole authored publications, any publication relying on data from the co-authored papers it had deemed unsafe should also be considered unsafe, that this applies only to the body of research covered by the 2019 enquiry, and that it considers its investigations concluded.

For a reader of this page the important sentence is what the statement does not say. It concerns personality and physical health data. It does not mention intelligence tests, and we did not find any source that extends its finding to Know Your Own IQ or to any online quiz. This page does not do so either. Equally, the finding gives no reason to treat his tests as validated. The test books stand or fall on their own documentation, which is the thing this page has been reading. A person's name is a good reason to look closely and a poor substitute for a norm table, whether the name is admired or disputed.

One practical consequence is how to read a claim such as "based on Eysenck's research." That phrase on the quiz's page describes inspiration, and it is compatible with items written recently by someone else. It tells the reader nothing about whether the items behave as his did, whether anyone has checked, or what the scale means. The same caution applies to any test that borrows a researcher's name. Ask for the manual, not the biography.

10 What would an adult need to see before trusting a score from a test like this?

Six items of documentation turn a quiz result into something that can be interpreted, and the Eysenck versions we read supply at most one or two of them publicly. The list below is built from the Standards sections quoted earlier and from the APA ethics provisions in the final section, and it works as a checklist for any test, book or app.

1. A described reference group, with ages, country, sampling method and participation (Standards 5.8 and 5.9).
2. The dates of norming, and evidence that the norms are still appropriate if the test is old (Standard 5.11).
3. A statement of how raw scores become the reported scale, so that users can judge its quality and precision (Standard 5.2).
4. Reliability and error: how much a score would move on retesting, shown as an interval and not only a point.
5. Validity evidence for the use you intend, which for an IQ number means evidence that the score reflects cognitive ability and not merely familiarity with the item format.
6. The administration conditions the norms assumed, and a note on what an unsupervised administration changes (Chapter 6 of the Standards).

A short test of any kind has a further limit that the list does not capture: breadth. Modern batteries are organized by the Cattell-Horn-Carroll model into broad abilities such as comprehension-knowledge (Gc), fluid reasoning (Gf), quantitative reasoning (Gq), visual processing (Gv), working memory (Gwm) and processing speed (Gs), and a Full Scale IQ summarizes several of them. The page on the CHC model lays this out. We have not read the items in any Eysenck book or in the online quiz, and we do not assign them to CHC abilities. The publisher says the book's challenges run from easy to difficult, and the quiz says only that one test cannot capture every aspect of intelligence. Both statements are modest and probably correct.

For contrast, the page on the WASI-II covers a short form of a Wechsler test. A short form is short by design, so what separates a documented short instrument from a quiz is the documentation behind the score, and not the number of items. The page on how IQ tests are made describes the development work that sits behind a normed instrument.

11 What should you do if you want a number you can use?

The right path depends on who will read the number, so start by asking that person which instrument and which qualifications they accept, and spend money only after the answer. A school, a clinician, a court, an employer or a high IQ society sets its own accepted instruments and conditions, so a free quiz or a self scored book cannot be assumed to count. The page on who can administer an IQ test sets out the qualification levels, and the page on official IQ tests lists the routes that count.

If the goal is private curiosity about your own profile, the reasonable options are of three kinds. A psychologist can give an individually administered battery and explain the result, which is the route described on professional IQ testing, and prices vary by clinic, as the page on how much an IQ test costs sets out. A society that runs its own supervised session, such as the one described on the page on the Mensa IQ test, decides whether a person qualifies under its own rules, and the page on high IQ society requirements compares them. And an online test with a published norm and a technical manual can give a documented score with the limits of unsupervised testing, which is where ACIS sits and is described in the next section.

The book and the free quiz have a role too. They are enjoyable ways to meet the format of reasoning problems and to see how you handle a clock, and the page on IQ test questions by type describes formats without reproducing items. What to avoid is carrying their output into a setting that asks for an IQ. A result that reads "130" on a self scored page can mislead a reader into skipping a proper assessment they actually need, or into quoting it to someone who will ask where it came from.

Three habits protect a reader whichever route is chosen. Keep the edition and date of whatever you took. Take one test at a time and avoid averaging scores from different instruments. And treat a single score as a point inside an interval, not as a fixed trait.

12 Where ACIS sits, and what a buyer should do

We sell ACIS, a separate online assessment, and it is not an Eysenck test, a substitute for the Eysenck books or a source of Eysenck scores; the right choice depends on what the score is for. ACIS has 20 subtests in six CHC domains, verbal comprehension, fluid reasoning, quantitative reasoning, visual spatial, working memory and processing speed, and reports a Full Scale IQ and six primary indices on a scale with a mean of 100 and a standard deviation of 15, with percentiles and a 95 percent confidence interval and adult norms for ages 16 to 90. Read on October 20, 2026, its one time forms were Quick at 15 dollars (6 subtests in 3 domains, about 45 minutes), Optimized at 30 dollars (13 subtests in 5 domains, about 110 minutes) and Full Scale at 50 dollars (all 20 subtests, about 175 minutes), with a free trial that needs no card, a 5 day quality guarantee and 30 days to complete. Prices can change, so check the current forms.

The limits are as important as the features. ACIS is taken online and unsupervised, in English only, so it shares the administration caveat of this page: nobody can confirm who sat the test or under what conditions. It is not a clinical or diagnostic instrument, and it is not for hiring, school accommodations or admission to high IQ societies. Its documentation is in the technical manual, and this page quotes nothing from it. Being documented is not the same as being equivalent to a Wechsler battery, and a reader should not treat an ACIS score as interchangeable with a clinician's report.

A buyer can reason in four steps. If someone else needs the number, ask them first. If the aim is to see a profile for yourself, choose an instrument that publishes its norm basis, reports an interval and states its own limits, and read those documents before paying. If you meet a quiz or book under a famous name, ask the six questions in the previous section. And keep the result inside the setting it was made for.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) is the framework this page uses to read every score: the norms must refer to a clearly described population, norming reports must state the sample and its dates, publishers must renorm often enough for interpretations to stay accurate, and the report on scores obtained without supervision should say that standardized conditions were not guaranteed. The American Psychological Association's Ethical Principles of Psychologists and Code of Conduct, effective January 1, 2017, adds guidance for psychologists. Standard 9.02(b) says they use assessment instruments whose validity and reliability have been established for use with members of the population tested, and that where this has not been established they describe the strengths and limitations of results and interpretation. Standard 9.06 asks them to take into account the purpose of the assessment and the characteristics of the person assessed, and to indicate significant limitations of their interpretations. Standard 9.07 says they do not promote the use of psychological assessment techniques by unqualified persons, except for supervised training. The code binds psychologists and not quiz publishers or readers, but its logic applies to a score of any origin: a number is only as good as the match between instrument, person and use.

13 Sources Behind This Page

Every fact about the Eysenck books and the online quiz comes from a publisher or library catalogue page, a 1990 review, King's College London's statement or the quiz's own page, every norm and testing principle comes from the 2014 Standards and the APA ethics code, and every figure on score drift or practice comes from a peer reviewed meta-analysis. Web pages were read on October 20, 2026 and can change. We did not have the book in hand, so nothing here is taken from inside it. The arithmetic in the table on score drift and the conversion of the practice effect to points are ours, and are labeled as such where they appear.

• Penguin Books. Know Your Own IQ by Hans Eysenck, catalogue page, ISBN 9781405932301, Penguin, paperback dated April 20, 2017, read October 20, 2026.
• Wellcome Collection. Know your own I. Q. by H. J. Eysenck, library catalogue entry, Penguin Books, Harmondsworth, Pelican Books, [1962], read October 20, 2026.
• Internet Archive. Catalogue records for Know your own I.Q. (2017), Check your own I.Q (Pelican A656, 1966), Test your IQ (Thorsons, 1994) and Test your child's abilities (Thorsons, 1996), read October 20, 2026.
• Open Library. Search results for Hans Eysenck titles on IQ, 17 records, read October 20, 2026.
• Fancher R. Look at me. London Review of Books, 1990, volume 12, issue 12, June 28. A review of Eysenck's autobiography Rebel with a Cause.
• King's College London. Statement on Hans Eysenck, including the update of October 6, 2025, read October 20, 2026.
• IDRlabs. Eysenck IQ Test, the online quiz's own page, read October 20, 2026.
• American Educational Research Association, American Psychological Association and National Council on Measurement in Education. Standards for Educational and Psychological Testing, 2014, chapters 5 and 6 and glossary, read in the open access PDF.
• American Psychological Association. Ethical Principles of Psychologists and Code of Conduct, effective January 1, 2017, Standards 9.02, 9.06 and 9.07.
• Flynn J R. The mean IQ of Americans: Massive gains 1932 to 1978. Psychological Bulletin, 1984, volume 95, issue 1, pages 29 to 51.
• Pietschnig J and Voracek M. One Century of Global IQ Gains. Perspectives on Psychological Science, 2015, volume 10, issue 3, pages 282 to 306.
• Trahan L, Stuebing K, Fletcher J and Hiscock M. The Flynn effect: A meta-analysis. Psychological Bulletin, 2014, volume 140, issue 5, pages 1332 to 1360.
• Hausknecht J, Halpert J, Di Paolo N and Moriarty Gerrard M. Retesting in selection: A meta-analysis of coaching and practice effects for tests of cognitive ability. Journal of Applied Psychology, 2007, volume 92, issue 2, pages 373 to 385.

14 Frequently Asked Questions