Most of you will at some point have been subjected to the ritual of taking a personality test when seeking a job. Three-quarters of large British companies now use them even though the tests have not been proven to predict winners better than chance.
When the tests were followed up years later to see if they successfully anticipated which candidates would succeed, it turned out you might as well have put the names in a hat: the scientific foundations of personality testing as an aid to job selection are just not there.
As part of his sales pitch, the psychologist flogging his test gets the executive to do it and then says something very general like 'you had difficulty in adjusting to your growing sexuality in childhood but this has become increasingly less of a problem'. How uncannily accurate, the exec thinks.
Their gullibility can be suprising. A mischievous psychologist once set up a table at a business conference with a machine that claimed to measure your personality from your business card. You inserted it at one end and after much flashing of lights, a very general personality profile came out at the other. Some senior executives were so impressed they asked where they could get hold of the machine. A teetotaller was suprised to be told he 'liked a drink or two', but he still believed the results.
The tests estimate personality traits, like extroversion or neuroticism, along a continuum from 'a little' to 'a lot'. Your normality is defined in relation to average scores for different groups, such as women, executives, young people or the university-educated.
Profiles are created for a specific job. For a clerical worker you might stipulate that the candidate should be above average for the Active category and not below it for Emotional Stability. 'Danger-zone' applicants are excluded.
Although the companies that supply the tests claim they should only be used as a guide and not interpreted without having met the person who has done the test, this is often not what happens in practice. You can simply send the completed test to some companies and their computer will carry out the whole analysis.
There is no sure scientific method for predicting performance from such measures. While people's track records and tests of intelligence and specific abilities are useful guides to how well they will execute the actual tasks, it is impossible to predict who will start signing cheques 'Pingu the Penguin' or claiming they are a poached egg, and who will not.
Worse still, it is impossible to spot a stinker. Some screwed-up people are immensely charming. Lacking identity, they look to you for self-definition. They are brilliant at working out who you want them to be, and acting it - very hard to spot in an interview.
Executives are supposed to have a good nose for these things. For most jobs, a personality test is an expensive waste of time.