Psychometrics

Psychometrics

Psychometrics is the science of measuring what cannot be observed directly. Nobody can see conscientiousness or anxiety. What can be observed is behavior: how someone answers questions, the choices they make, how they act over time. Psychometrics supplies the methods for inferring the hidden quantity from that visible evidence, and for checking whether the inference can be trusted.

Core ideas

• Latent construct — the hidden quantity being measured: a trait, an ability, an attitude. It is never observed itself; it is defined by its pattern of effects on behavior.
• Instrument — the tool used to gather evidence, most often a questionnaire of rated items (“strongly disagree” to “strongly agree”). Each item is a noisy signal; many items combined give a stable score.
• Reliability — does the instrument give consistent results? Items meant to measure the same trait should agree with one another, and the same person should score similarly when retested.
• Validity — does it measure what it claims to? A valid measure predicts the real-world behavior associated with the trait, and can be told apart from measures of other traits.
• Factor analysis — the statistical technique used to find which observed behaviors cluster together, and so how many underlying dimensions are needed to explain them.

From measurement to models of personality

Modern personality models are products of psychometrics. Researchers began from the lexical hypothesis — the idea that the personality differences people care about most become encoded as words in everyday language. They gathered thousands of descriptive adjectives, had people rate themselves and others on them, and used factor analysis to uncover the structure underneath.

That line of work runs from Cattell’s 16PF in the 1940s, through the Big Five, to the six-factor HEXACO model, whose lexical studies across many languages kept producing six factors rather than five. See Psychological Foundations: Modeling Personality.

How NeoThymos uses it

NeoThymos runs psychometrics in the opposite direction. A psychometric instrument starts with behavior and infers trait scores. NeoThymos starts with trait scores — the 25 facet values of a persona’s Core Personality, using five bands for each facet — and synthesizes the character and behavior those scores imply.

That is what psychometrically grounded means here:

• A persona’s personality is specified in the coordinates of a model that decades of measurement research have shown to be reliable, valid and predictive of real behavior — not in an ad-hoc list of adjectives.
• The personality can be reasoned about using what that research says about how traits relate to one another, including the trait patterns that predict problematic conduct (see The Dark Spectrum of Personality).

For the facets themselves, see Core Personality & The HEXACO Personality Model.