I was recently reviewing some psychological lectures for my real job. One of these was on personality tests. The speaker mentioned the Myers-Briggs test, explaining that, while well known (I personally know it from a Dilbert cartoon) the Myers-Briggs test isn't recognised as being scientifically valid so is largely ignored by the field of psychology. I tweeted this fact, thinking it would be of passing interest to a few people. I was unprepared for the intensity of the replies I got. I learned several things that day.

1. The Myers-Briggs Type Indicator (MBTI) is used by countless organisations and industries, although one of the few areas that doesn't use it is psychology, which says a lot.

2. Many people who have encountered the MBTI in the workplace really don't have a lot of positive things to say about it.

3. For some organisations, use of the MBTI seemingly crosses the line into full-blown ideology.

So how did something that apparently lacks scientific credibility become such a popular and accepted tool?