The Eysenckian approach of broad personality dimensions initially influenced the personality-based measures of schizotypy with both the original and revised
2 The measures included in this section refer to those designed to directly assess
schizotypy. For example, there are a plethora of paranoid ideation scales that measure components of schizotypy (e.g., the Paranoid Thoughts Scale measures the schizotypal feature of Ideas of Reference; Green et al., 2008), but these are not included here as they do not directly measure schizotypy as a construct itself.
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Psychoticism Scales (see Table 1; Eysenck & Eysenck, 1975; Eysenck, Eysenck, & Barrett, 1985). The original scale had content directly relevant to psychosis, but suffered from poor internal consistencies and low endorsement rates – the very antithesis of the intention of normally distributed personality traits (Claridge, 1997; Mason, 2015). Eysenck et al.’s (1985) revision aimed to amend the weaknesses of the original scale, but instead moved the focus of the scale towards items addressing antisocial, impulsive, and nonconformist traits. This shift of focus led researchers to label the scale as more of a measure of psychopathy as opposed to psychosis proneness (Zuckerman, 1993). Irrespective of the label, the Psychoticism Scales have been criticised on the grounds of their specificity and criterion validity (Claridge, 1983), as well as issues with predictive validity (Chapman, Chapman, & Kwapil, 1994). For example, in factor analytic studies, instead of loading on to psychotic-like factors, scores on the Psychoticism Scales have tended to load on to factors reflecting impulsive non-conformity. This has brought into question the scale’s relevance for use in psychosis research (Bentall et al., 1989; Claridge et al., 1996; Raine & Allbutt, 1989). However, from this, successive authors have sought to construct improvements to broaden the trait content and issues with validity (Claridge, 1997).
Nielsen and Petersen (1976) developed a scale of ‘schizophrenism’, a
subschizophrenic trait characterised by withdrawal and cognitive abnormalities. The authors reported inter-scale correlations that were troublesome (rs = .53-.78), as they were indicative of potential multicollinearity. Rust (1988) later developed the Rust Inventory of Schizotypal Cognitions (RISC), a scale designed to tap different aspects of ‘psychoticism’ compared to the Psychoticism Scale. The RISC measures mild
schizotypal cognitions from the positive spectrum of traits and focuses on avoidance of clear pathological items present in other scales (e.g., the Chapman scales; see Section 1.3.2).
Table 1. Personality-Based Measures of Schizotypy Measure Formulation Internal
Consistency
Content
Psychoticism Scales
Original scale
Eysenck and Eysenck (1975)
Single scale; 25 items
.68-.74 Description of features including aggressiveness, egocentrism, impulsivity, creative, lack of empathy, and impulsiveness.
Revised scale
Eysenck et al. (1985)
Single scale; 32 items
.76-.78 Similar content to original scale but with greater focus on antisocial, impulsive, and nonconformist traits.
Schizophrenism Scale
Nielsen and Petersen (1976)
Single scale; 14 items
Not Reported
Description of features associated with attentional difficulties and social anxiety Rust Inventory of Schizotypal Cognitions Rust (1988) 2 subscales; 26 items
.67-.77 Cognitive schemata of suspicion, magical ideation, ritual, subjectivity, thought isolation, and self-delusion, which are not uncommon in the normal population.
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Oxford-Liverpool
Inventory of Feelings and Experiences (O-LIFE)
O-LIFE
Mason et al. (1995)
4 subscales; 104 items
.77-.89 Unusual experiences relating to magical thinking and hallucinations; cognitive disorganisation such as social anxiety, poor attention, and moodiness; introvertive anhedonia characteristics including social and physical anhedonia, and avoidance of intimacy. Impulsive non-
conformity traits relating to eccentric behaviour and self-control.
O-LIFE Short Mason et al. (2005)
4 subscales; 43 items
.62-.80 Similar content to original scale with reduced item set.
Community Assessment of Psychic Experiences
Stefanis et al. (2002)
3 subscales; 40 items
.62-.64 Positive psychotic-like experiences; negative symptoms including emotional deficits, lack of motivation, and social disinterest; and cognitive symptoms of depression.
Indeed, Miller, Lawrie, Byrne, Cosway, and Johnstone (2002) suggested that high scores on the RISC represent the existence of psychotic symptoms. However, Chapman, Chapman, and Kwapil (1995) suggested that the main reason for
investigating schizotypal cognitions was to diagnose SPD and suggested that there was little evidence of the RISC detecting SPD in a non-psychotic population.
One of the most widely-used personality measurements of schizotypy is the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE; Mason et al., 1995), which was developed from the Combined Schizotypal Traits Questionnaire (CSTQ; Bentall et al., 1989), a combination of 15 scales that measures different aspects of schizotypy. Although comprehensive, the CSTQ is not especially practical for use in experimental research, as administration of its 410 items is time-consuming and highly repetitive. The O-LIFE consists of four scales derived from four factors through factor analysis of the scales in the CSTQ (Claridge et al., 1996): Unusual Experiences,
Cognitive Disorganisation, Introvertive Anhedonia, Impulsive Non-conformity, with
three other scales of Eysenck’s Extraversion Scale, a lie scale, and Claridge’s Schizotypal Traits Questionnaire (STA; based on diagnostic criteria for schizotypal personality disorder; see Section 1.3.2). The latter three scales were included as a foundation of known validity and reliability (Burch, Steel, & Hemsley, 1998). The four new scales set out to measure different aspects of the schizotype, with Cognitive
Disorganisation and Unusual Experiences reflecting positive symptomatology, Introvertive Anhedonia reflecting negative symptoms, and Impulsive Nonconformity
having high positive loading with Eysenck’s Psychoticism Scale (Claridge et al., 1996). Rather than serving quasi-clinical aims, the primary use of the O-LIFE has been to explore relationships with a range of preferences, behaviours, and task performances including creativity, laterality, mentalising, and neurocognition (Mason, 2015).
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The Community Assessment of Psychic Experiences (CAPE; Stefanis et al., 2002) was developed to measure the lifetime prevalence of psychotic-like experiences in the general population (Konings, Bak, Hanssen, van Os, & Krabbendam, 2006; Stefanis et al., 2002), and findings with this scale indicated self-reported psychotic-like experiences to be stable, reliable, and valid (Konings et al., 2006). The CAPE is based in part on the more clinical Peters Delusional Inventory (Peters et al., 1991), with two additional hallucination items and 14 negative items. The CAPE reflects positive and negative psychotic symptoms, yet is limited as an overall measure of schizotypy because of the lack of a disorganised factor.