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Quite Interesting IQ test

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Kevin Langdon's 'Omni' IQ test

First published in the April 1979 edition of Omni magazine in an article by Scot Morris.

This page is under development, when finished there will be 56 questions in total on the right hand menu.

Standard IQ tests, such as the famous Stanford-Binet scale, are designed to measure scores clustering around 100, the average in the human population. The test reproduced here was designed in 1979 by San Fransisco systems analyst Kevin Langdon to measure IQs in the range 125 to 180, and was claimed at that time to be the world's most difficult IQ test. It is unsupervised and untimed. The only rule is that you are honour-bound to take it on your own, and without help, but you may spend as long as you want on it - hours, days or months. What matters is not the time taken, nor any special expertise or knowledge you may have, but just your power of attention and ability to find the only logical solution by thinking deeply.

When this test was first published, those brave enough to try it were asked to send their completed answer sheet to Omni for marking, and received an IQ report in return. The correct answers were not revealed. This raises an interesting question as to who decides when an answer is correct.  The designer would presumably aim to design each question so that the correct solution, when properly understood, is self-evidently the only possible solution: simple, elegant and satisfying. Then the quiz-taker can be confident that they have found the right answer.

Way back in 1979, after a month of concentrated deliberation, I sent in my score sheet and received a reply saying my IQ was 169. At the time I wasn't sure of the answers to  about 6 of the 56 questions so I had to make an educated guess, eliminating the obviously wrong suggested answers. Now, looking again after 40 years of subconscious deliberations, ha ha, I have a satisfying answer for all the questions, each with a high probability of being the same as Langdon's secret answer. Interestingly, I feel smarter these days, albeit older and slower, in that I can now easily see the answers to a couple of the questions that vexed me back then.


This test has not been marked by Langdon for many years. Out of respect for the spirit of the original, I do not wish to reveal my set of answers. However, if you want to test yourself for fun (yeah right - fun!), you can always send me an email with all your final answers at once, but only when you are sure you are done!
I will be able to reply with a single number: the number of your answers with which I agree. This will be a close approximation to the correct score. If our number of disagreements was low, say less than 5 out of 56, we could discuss the reasons.

 Langdon provided a norming document with his original marking sheet, and some supplementary information in the May 1980 edition of his Sigma Four magazine. Thanks to Darryl Miyaguchi for those links. Those two docs might prove useful in estimating an IQ from a high Langdon test score, although I have not yet had time to consider this.    smiling face emoji

In the original scoring method, in order to counteract the possibility of guessing (with a 20% chance of being right for each multiple choice question) a 'raw score' was computed equal to the number of correct answers minus one fourth of the wrong answers. Barring statistical flukes, this means a set of all-guessed answers would score zero.


Why have I bothered to reproduce this test?  This test is fascinating to me because there is no time limit. This test is a genuine test of logical problem-solving ability, and not of memory, general knowledge or literary learning, which are great skills but not so useful when faced with a dilemma. In my academic life as a research physicist, I witnessed quite a few 'whizz-kid' types who took pride in being the fastest to offer solutions to any problem in our laboratory brain-storming sessions. I believe that their strategy (perhaps unconscious) involved aiming to be right around 90% of the time, and not to worry about any confounding doubts or alternative theories that slow down thinking. Perfectly legitimate, and desirable in many circumstances. However, to try and be right 99% of the time, those doubts need to be examined, and that takes time. The danger therein is of appearing to be a 'reliable diligent plodder'.

Still - it takes all sorts. What's nice about Langdon's 'Omni' test is that it gives deep thinkers a chance to shine. I hope you have fun with it, to answer my initial question. And a big thank you to Kevin Langdon for producing such a beautiful set of questions.

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