stylistic:tone
Measurement

Like other personality traits, neuroticism is typically viewed as a continuous dimension rather than a discrete state.

The extent of neuroticism is generally assessed using self-report measures, although peer-reports and third-party observation can also be used. Self-report measures are either lexical or based on statements. Deciding which measure of either type to use in research is determined by an assessment of psychometric properties and the time and space constraints of the study being undertaken.

Lexical measures use individual adjectives that reflect neurotic traits, such as anxiety, envy, jealousy, and moodiness, and are very space and time efficient for research purposes. Lewis Goldberg (1992) developed a 20-word measure as part of his 100-word Big Five markers. Saucier (1994) developed a briefer 8-word measure as part of his 40-word mini-markers. Thompson (2008) systematically revised these measures to develop the International English Mini-Markers which has superior validity and reliability in populations both within and outside North America. Internal consistency reliability of the International English Mini-Markers for the Neuroticism (emotional stability) measure for native English-speakers is reported as 0.84, and that for non-native English-speakers is 0.77.

Statement measures tend to comprise more words, and hence consume more research instrument space, than lexical measures. Respondents are asked the extent to which they, for example, "Remain calm under pressure", or "Have frequent mood swings". While some statement-based measures of neuroticism have similarly acceptable psychometric properties in North American populations to lexical measures, their generally emic development makes them less suited to use in other populations. For instance, statements in colloquial North American English like "feeling blue" or "being down in the dumps" are sometimes hard for non-native English-speakers to understand.

Neuroticism has also been studied from the perspective of Gray's biopsychological theory of personality, using a scale that measures personality along two dimensions: the behavioural inhibition system (BIS) and the behavioural activation system (BAS). The BIS is thought to be related to sensitivity to punishment as well as avoidance motivation, while the BAS is thought to be related to sensitivity to reward as well as approach motivation. Neuroticism has been found to be positively correlated with the BIS scale, and negatively correlated with the BAS scale.

Neuroticism has been included as one of the four dimensions that comprise core self-evaluations, one's fundamental appraisal of oneself, along with locus of control, self-efficacy, and self-esteem. The concept of core self-evaluations was first examined by Judge, Locke, and Durham (1997), and since then evidence has been found to suggest these have the ability to predict several work outcomes, specifically, job satisfaction and job performance.

There is a risk of selection bias in surveys of neuroticism; a 2012 review of N-scores said that "many studies used samples drawn from privileged and educated populations".

Neuroticism is highly correlated with the startle reflex in response to fearful conditions and inversely correlated with it in response to disgusting or repulsive stimuli. This suggests that Neuroticism may increase vigilance where evasive action is possible but promote emotional blunting when escape is not an option. A measure of the startle reflex can be used to predict the trait neuroticism with good accuracy; a fact that is thought by some to underlie the neurological basis of the trait. The startle reflex is a reflex in response to a loud noise that one typically has no control over, though anticipation can reduce the effect. The strength of the reflex as well as the time until the reflex ceases can be used to predict both neuroticism and extraversion.