The psychometric industry in the UK is worth many millions of pounds and it continues to grow. It is big business. The majority of FTSE 250 companies and over 80% of the public sector regularly use personality assessments for recruitment, selection and development purposes.

Personality assessments typically fall into two sorts - Type and Trait measures. Type measures consider that personality can be grouped into discrete categories (e.g. extrovert or introvert). These include MBTI, Insights Discovery and DISC. Trait measures consider that these characteristics can be placed on a continuum (e.g. in a middling position on the introvert/extrovert continuum). These include 'Big Five' tools such as NEO PI, Hogan and OPQ. Type measures allow for a limited number of personality characteristic combinations. In contrast, Trait measures allow for a potentially infinite number of trait variations on the continuum basis. They are fundamentally different.

​Tools which categorise personality into types are considered the least valid way of measuring personality and produce inaccurate and misleading assessments. As a consequence they are not very effective in achieving the two primary purposes of using them:
​1. Raising self-awareness (for development purposes)
2. Predicting future behaviour (for recruitment and selection purposes)​

​Trait measures on the other hand have a considerable weight of evidence to support them. There is plenty of evidence that personality is structured around traits and not types. For a particular trait we may 'sit' somewhere on a continuum between very low and very high but we would all score somewhere on that trait. Person A might be a bit more extrovert than Person B but that doesn't mean they have a different personality type, or that they might not flex that extroversion up or down a little in different situations or moods. Type labels essentially box people into a tight space which allows little room for that flexing.​

Why does this matter?

Because tools which are invalid and inaccurate will not only to fail to achieve their purpose but in the process will mislead, waste money and may cause harm. Surely, that's unethical?

Yet while Trait-based assessments are gaining significant ground in the psychometric market, Type-based assessments are still prominent and widely used.

Why do they endure?

We think there are many reasons for this, not least because accreditation training is expensive and knowledge about different tools is patchy. These are also some of the common reasons psychologists, academics and evidenced-based coaches put forward to explain this. But we think there is also another reason and this view is based on our anecdotal experience. It concerns the reports.

People love their Insights Discovery (and similar) reports. They are energised by the findings, will proactively send us (as coaches) their prior reports, and report finding them very useful. With high face validity, these reports also look great, they are simple and quick to understand and they lend themselves to immediate action. In contrast many of the trait-based assessment reports do few of these things. They're accurate and comprehensive but also lengthy and complicated at first sight and there is more reading to do.

Most people we work with have no idea of the relative merits of these tools but will take them on trust and at face value. In a busy schedule who wouldn't prefer the report which looks right and is easy to use? So, our message to the developers of those preferred Trait assessments, please look again at your reports - further enhancement would make our work promoting accurate information much easier!

We'd love to know your views and experiences on personality assessment, Please do share any comments below. If you'd like to discuss the use of psychometrics in your team or organisation do get in touch.