What is the science behind AssessFirst?


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“The AssessFirst personality questionnaire wasn’t just designed to assess personality, but also to predict success.”

Simon Baron

Chief Scientist – AssessFirst

The AssessFirst personality questionnaire was developed by a team of human potential assessment experts, comprised of psychologists and psychometricians. This development was carried out according to industry standards, in the strictest compliance with practices recommended by the American Psychological Association.

Why personality?

For dozens of years, research in psychology and management has been uncovering the exceptional impact that personality has on an individual’s adaptation to and success in the workplace. This is because the results that we achieve every day, whether in our personal or working life, are directly linked to the behaviours that we display. Because personality is the best known predictor of behaviour to date, its assessment has quite naturally become crucial in the field of recruitment, orientation, mobility management and the development of individuals within organisations.

The Big Five model as a starting point

The theoretical basis on which the AssessFirst personality questionnaire draws is the Big Five model. This model, which was determined decades ago by Costa and McCrae in particular, provides a description of personality based on five key factors. These five factors are considered by the international scientific community as the fundamental components of personality. The Big Five model is doubly advantageous. 

  • Firstly, it is a cross-cultural model: These five key factors are found in every culture. Therefore, it can be used to predict how any individual in the world functions.
  • Secondly, it is a proven model: Over 40 years of research with convergent results attest to its robustness.

Expanding to 20 personality traits for more accuracy

To create the most accurate description possible of how people naturally function, each of the five factors in this model has been subdivided by AssessFirst into four sub-factors or facets. In total, 20 personality traits have therefore been integrated into the AssessFirst personality questionnaire.

Validation through three key criteria

Before it was launched, the AssessFirst personality questionnaire was validated based on three key criteria.

  • Validity: The validity of a personality questionnaire is down to its ability to effectively measure what it is supposed to measure.

If the questionnaire does not assess what it is supposed to assess (for example, if a scale called extraversion measures something other than extraversion), it becomes difficult to make sense of the results obtained by a person and to make informed decisions based on their profile. It is crucial for all of the questions associated with a trait to correctly assess this trait specifically and to not address other traits.

  • Reliability: Reliability is to do with a questionnaire producing consistent measurements of the phenomena that it assesses.

If a candidate takes the same questionnaire twice at two different times and obtains radically different scores, the questionnaire is not reliable. It is essential for the results to have a certain stability, without which it is impossible to use them to predict how successful individuals will be.

  • Sensitivity: Sensitivity refers to the ability of a personality questionnaire to make subtle distinctions between different people.

If everyone obtains more or less the same score in a questionnaire, it is not sensitive. It is important for the general population to be evenly distributed across all of the score scales (from 1 to 10) and for each of the traits assessed.

Paying special attention to predictive validity

At AssessFirst, we pay very special attention to what is known as the predictive validity of our personality questionnaire. A questionnaire’s predictive validity is its ability to effectively predict an external criterion, such as a person’s suitability for their role or the objective performance level that they are able to deliver. Every year, we carry out dozens of studies for our clients that indicate the strong link between certain characteristics of their populations in terms of personality and various external criteria, such as the revenue generated by sales staff and how long individuals remain in their jobs. For example, for one of our clients we were able to establish that sales staff who have certain characteristics are on average 25% more effective than the average salesperson who does not have these characteristics. This type of study enables our customers to implement predictive success models, which they use as a filter for their candidate prescreening procedures. These predictive models often complement (or even replace) the traditional method of CV-based preselection.


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AssessFirst is one of 65 members affiliated with the International Test Commission (ITC).
The ITC is internationally responsible for psychometric best practice standards. Through the recommendations of their experts and working groups, they promote the development and creation of reliable and ethical tests throughout the world. This affiliation also comes back to our desire to commit ourselves to the international assessment community.
More than 10,000 recruiters worldwide use AssessFirst to assess their candidates’ personality and potential. Join them today.