Do sex differences in emotionality mediate sex differences in traits of psychosis-proneness?

The aim of the study was to determine if sex differences in emotionality might account for sex differences in distinct traits of proneness to psychosis (or "schizotypy"). Females report higher levels of "positive" schizotypy (e.g., magical thinking) than males, along with a tendency toward greater schizotypal disorganisation, whereas males report higher levels of "negative" schizotypal traits, such as social anxiety (Jackson & Claridge, 1991; Raine, 1992). Given the affect-oriented nature of "negative" schizotypal traits, we tested the hypothesis that higher levels of "negative" schizotypy among males would be accounted for by more general sex differences in emotionality; that is, by less frequent and less intense emotional experiences. A total of 81 student participants were administered the Cognitive-Perceptual Deficits, the Disorganisation, and the Interpersonal Deficits components of Raine's (1991) Schizotypal Personality Questionnaire (SPQ), indexing respectively, "positive" schizotypy, schizotypal disorganisation, and "negative" schizotypy. Frequency of emotional experience was assessed using the Emotionality subscale (Buss & Plomin, 1984) and intensity, the Affect Intensity Measure (Larsen & Diener, 1987). As predicted, males scored significantly higher than females on the SPQ Interpersonal Deficits component but no sex differences emerged for the other two components. Males reported significantly less intense, although not less frequent, experiences than females. A reduced intensity of positive emotions in particular was found to mediate the sex difference in "negative" schizotypy. Our results suggest that a less intense experience of positive affect might contribute to males' propensity to develop negative symptoms should a schizophrenic breakdown occur.     

Effects of increasing cognitive load on sustained attention tasks in schizophrenic disorders and schizotypy

In this study we analyze the attentional performance using different cognitive load attentional tasks: low-load cognition (0-CPT) and high-load cognition (DS-CPT). Participants were a group of schizophrenic patients and two groups of normal population psychometrically classified as low schizotypy and high schizotypy according to the SPQ. Our results show that schizophrenic patients were more sensitive to increments on cognitive load, being their attentional performace worse than the rest of the groups. The lack of significant findings in vigilance on the schizotypal traits group is discussed in terms of conceptual and methodological issues about the utility of psychometric strategies to identify vulnerable populations within the spectrum of the schizophrenic disorders.     

Three-factor model of Schizotypal Personality in a British Christian sample

The three-factor structure of schizotypy, as measured through the Schizotypal Personality Questionnaire (SPQ), was assessed in a non-clinical Christian sample of 161 British adults from a wide range of denominational backgrounds. Participants were recruited through non-random purposive sampling. The trifactor model was unambiguously replicated. Furthermore, the SPQ exhibited excellent internal consistencies (range 0.73 to 0.97), while Confirmatory Factor Analysis and cross-instrument comparisons with Eysenck's Psychoticism scale indicated that elements of its convergence and discriminant validities were highly acceptable. Although this study identified some minor issues that require attention, overall, the SPQ appears to be a rather powerful and highly stable measure of schizotypy that can reliably be used in schizophrenia-related research with Christians.     

Validation of the Multidimensional Schizotypy Scale-Brief in Two Large Samples

This study reports on an initial examination of the construct validity of the Multidimensional Schizotypy Scale-Brief (MSS-B) and the first investigation of its psychometric properties outside of its derivation samples. The MSS-B contains 38 items that assess positive, negative, and disorganized schizotypy and has comparable content coverage and psychometric properties as the original 77-item Multidimensional Schizotypy Scale. Two large samples (n?=?1430 and 1289) completed the MSS-B, as well as measures of schizotypal personality traits and the Five-Factor Model of Personality. MSS-B scores were computed from the full-length scale in sample 1, whereas participants in sample 2 were administered the MSS-B. The psychometric properties and intercorrelations of the MSS-B subscales were consistent with findings from the original derivation samples, with no shrinkage in reliability. In terms of relations with schizotypal traits, the MSS-B positive schizotypy dimension had its strongest association with cognitive-perceptual schizotypal traits, MSS-B negative schizotypy had its strongest association with interpersonal schizotypal traits, and MSS-B disorganized schizotypy had its strongest association with disorganized schizotypal traits. The schizotypy dimensions were characterized by hypothesized patterns of distinct associations with the Five-Factor Model. The present findings are consistent with results from the full-scale MSS.     

Confirmatory factor analysis of the three-factor structure of the schizotypal personality questionnaire and Chapman schizotypy scales

We examined the factor structure of the Schizotypal Personality Questionnaire (SPQ; Raine, 1991), using confirmatory factor analysis in 3 experiments, with an aim to better understand the construct of schizotypy. In Experiment 1 we tested the fit of 2-, 3-, and 4-factor models on SPQ data from a normal sample. The paranoid 4-factor model fit the data best but not adequately. Based on the strong basis for the Raine 3-factor model we attempted to improve the fit of the 3-factor model by making 3 modifications to the Raine model. These modifications produced a well-fitting model. In Experiment 2 the good fit of this modified 2-factor model to SPQ scores was replicated in an independent normal sample. In Experiment 3, the modified 3-factor model was successfully extended to include the 3 Chapman schizotypy scales. Together these 3 experiments indicate that the 3-factor model of the SPQ, albeit with some slight modifications, is a good model for schizotypy structure that is not restricted to 1 measure of schizotypal personality traits.     

Correlations between psychometric schizotypy,scan path length,fixations on the eyes and face recognition

Psychometric schizotypy in the general population correlates negatively with face recognition accuracy, potentially due to deficits in inhibition, social withdrawal, or eye-movement abnormalities. We report an eye-tracking face recognition study in which participants were required to match one of two faces (target and distractor) to a cue face presented immediately before. All faces could be presented with or without paraphernalia (e.g., hats, glasses, facial hair). Results showed that paraphernalia distracted participants, and that the most distracting condition was when the cue and the distractor face had paraphernalia but the target face did not, while there was no correlation between distractibility and participants’ scores on the Schizotypal Personality Questionnaire (SPQ). Schizotypy was negatively correlated with proportion of time fixating on the eyes and positively correlated with not fixating on a feature. It was negatively correlated with scan path length and this variable correlated with face recognition accuracy. These results are interpreted as schizotypal traits being associated with a restricted scan path leading to face recognition deficits.     

A simple method for measuring brain asymmetry in children: Application to autism

A device for measuring signal transfer within and between hemispheres has been developed at the Center for Neuropsychological Research at the University of Trier, Germany. It contains two identical panels allowing both tactile stimulation and motor response with buttons for the fingers of each hand. The buttons have two functions. They can exert a slight tactile stimulation to a finger, and they can be pressed down by the finger to provide a motor response to the tactile stimulation allowing measuring the response time. The device was used for measuring brain asymmetry in tactile processing autistic children. The participants were given a finger tapping test followed by the procedures with unilateral and bilateral processing of tactile stimulation. All participants responded positively to the test procedure and accepted it as a kind of game. The results indicated that brains were more asymmetrical in autistic children than in controls: The right hemisphere functioned quicker than the left hemisphere.     

Individuals with pronounced schizotypal traits are particularly successful in tickling themselves

We assessed self-tickling sensations in a group of participants high in schizotypal traits (n = 27) and group of participants low in schizotypal traits (n = 27). The groups were formed by screening a pool of 397 students for extreme scores in the French version of the Schizotypal Personality Questionnaire. As observed in a previous study involving psychiatric people with auditory hallucinations and/or passivity experiences our results showed that self-applied tactile stimulations are felt to be more ticklish by healthy individuals high in schizotypal traits. In contrast, there were no significant intergroup differences in the mean tickle rating in the externally-produced tickling condition. Furthermore, more successful self-tickling was associated with more frequent self-reports of unusual perceptual experiences (such as supernatural experiences) and passivity experiences in particular (such as a feeling of being under the control of an outside force or power).     

Handedness, emotional problems, and schizotypy

The purpose of this study was to analyse the relationship between emotional or behavioural problems and schizotypy. An assessment of handedness and schizotypal personality traits were also performed by means of the Thinking and Perceptual Style Questionnaire, the Multidimensional Schizotypal Traits Questionnaire, the Edinburgh Handedness Inventory, and the Youth Self-Report. The sample comprised 296 participants with a mean age of 13.8 and a standard deviation of 1.34. Data indicate that adolescents with high scores on psychometric factors of schizotypy displayed higher patterns of problem behaviours as well as a significant difference in all the core factors of the Youth Self-Report, compared to those who scored low on these measures. Discriminant analysis showed that the core factors of the Youth Self-Report correctly classified 84% of the adolescents with high or low scores on psychometric schizotypy. Lastly, no significant association between the factors of schizotypy and left-handedness, right-handedness, or mixed-handedness was found.     

Reaction time slowing during high-load, sustained-attention task performance in relation to psychometrically identified schizotypy

Prior research has demonstrated a reliable deficit in performance accuracy (e.g., d') on sustained-attention tasks in relation to psychometrically identified schizotypy and clinically diagnosed schizotypal psychopathology. The present study sought to expand the understanding of sustained-attention performance in relation to psychometric schizotypy through a study of reaction time (RT) performance. In this study, the author examined performance accuracy and RT on a high-load, sustained-attention task, the Continuous Performance Test-Identical Pairs (CPT-IP) version, in 31 high Perceptual Aberration Scale (PAS) and 26 normal control (control PAS) subjects from a large university population. High PAS (psychometric schizotypy) subjects displayed significantly longer RT performance on the CPT-IP relative to controls. The RT slowing was not explained by mental state or general intellectual ability factors. Contrary to expectation, a difference in performance accuracy (e.g., d') was not observed between the groups; however, power and other considerations cloud the interpretation of this finding. The meaning of the observed RT slowing is examined and its relation to current models of the development of schizophrenia is discussed.     

Lost in the move? Secondary task performance impairs tactile change detection on the body

Change blindness, the surprising inability of people to detect significant changes between consecutively-presented visual displays, has recently been shown to affect tactile perception as well. Visual change blindness has been observed during saccades and eye blinks, conditions under which people’s awareness of visual information is temporarily suppressed. In the present study, we demonstrate change blindness for suprathreshold tactile stimuli resulting from the execution of a secondary task requiring bodily movement. In Experiment 1, the ability of participants to detect changes between two sequentially-presented vibrotactile patterns delivered on their arms and legs was compared while they performed a secondary task consisting of either the execution of a movement with the right arm toward a visual target or the verbal identification of the target side. The results demonstrated that a motor response gave rise to the largest drop in perceptual sensitivity (as measured by changes in d′) in detecting changes to the tactile display. In Experiment 2, we replicated these results under conditions in which the participants had to detect tactile changes while turning a steering wheel instead. These findings are discussed in terms of the role played by bodily movements, sensory suppression, and higher order information processing in modulating people’s awareness of tactile information across the body surface.     

Disrupting somatosensory processing impairs motor execution but not motor imagery

While motor imagery (MI) is thought to be ‘functionally equivalent’ with motor execution (ME), the equivalence of feedforward and feedback mechanisms between the two modalities is unexplored. Here, we tested the equivalence of these mechanisms between MI and ME via two experiments designed to probe the role of somatosensory processing (Exp 1), and cognitive processing (Exp 2). All participants were engaged in a previously established force-matching task adapted for MI. A reference force was applied (on scale of 1–10, with higher numbers indicative of greater force) to one index finger while participants matched the force with their opposite index finger via ME or MI (control conditions). Participants then rated the force on the same scale of 1–10. Exp 1: Participants (N = 27) performed the task with tactile stimulation (ME+TAC, MI+TAC) in addition to control conditions. Exp 2: Participants (N = 26) performed the task in dual-task conditions (ME+COG, MI+COG) in addition to control conditions. Results indicate that (Exp 1) tactile stimulation impaired performance in ME but not MI. Dual-task conditions (Exp 2) were not shown to impair performance in either practice modality. Findings suggest that while somatosensory processing is critical for ME, it is not for MI. Overall we indicate a functional equivalence between feedforward/back mechanisms in MI and ME may not exist.     

Tactile expectations and the perception of self-touch: An investigation using the rubber hand paradigm

The rubber hand paradigm is used to create the illusion of self-touch, by having the participant administer stimulation to a prosthetic hand while the Examiner, with an identical stimulus (index finger, paintbrush or stick), administers stimulation to the participant’s hand. With synchronous stimulation, participants experience the compelling illusion that they are touching their own hand. In the current study, the robustness of this illusion was assessed using incongruent stimuli. The participant used the index finger of the right hand to administer stimulation to a prosthetic hand while the Examiner used a paintbrush to administer stimulation to the participant’s left hand. The results indicate that this violation of tactile expectations does not diminish the illusion of self-touch. Participants experienced the illusion despite the use of incongruent stimuli, both when vision was precluded and when visual feedback provided clear evidence of the tactile mismatch.     

An analysis of tactile letter confusions

A confusion matrix of the whole block capital letters of the alphabet was obtained so as to examine the nature of tactile letter recognition, using a 17 by 17 matrix of tactile stimulators placed against blind subjects’ backs. A hierarchical cluster analysis and a nonmetric multidimensional scaling technique were applied to the matrix. The results of the two analyses were consistent with each other and indicated that at least three independent basic letter features—enclosing shapes, vertical parallel lines, andangle of lines—play important parts in tactile letter recognition. Most confusion may be attributable to displacement of the apparent loci, omission or fusion of loci of stimulation, and failure to detect gaps in the tactile letters.     

Psychometric schizotypy and motor performance

Motor abnormalities have long been a focus in discussions of schizophrenia. The present study used a newly developed line drawing task to examine fine motor performance and psychometrically assessed schizotypy in a large, randomly ascertained sample of young adults (N = 120) with no history of psychosis. Poor motor performance on the line drawing task, indexed by root-mean-square error (RMS), was significantly related to 4 separate psychometric measures of schizotypy in the overall sample. The psychometric schizotypy-RMS association remained significant for 2 of the schizotypy measures even when the effects of intellectual functioning, mental state factors, and sustained attention were statistically controlled in a regression analysis. The status of the line drawing index as a schizophrenia liability measure is discussed.     

The relationship between measures of creativity and schizotypy

The aim of this study was to determine the extent to which a measure of multidimensional schizotypy and intelligence predicted measures of creativity, as assessed by self-rated creativity, a measure of the creative personality (CPS: Gough, 1979) and an inventory of creative behaviours. Additionally an aggregation of the three different measures; total creativity was examined. 140 participants completed the creativity measures, a general intelligence test (Wonderlic Personnel Test: Wonderlic, 1992) in addition to a multidimensional schizotypy inventory (O-LIFE: Mason, Claridge, & Jackson, 1995). The Unusual Experiences and Impulsive Nonconformity dimensions of the O-LIFE were positively and significantly related to creativity. The Cognitive Disorganisation dimension was found to be negatively and significantly related to creativity. The implications of the findings were discussed.     

The ability to self-tickle following Rapid Eye Movement sleep dreaming

Self-produced tactile stimulation usually feels less tickly--is perceptually attenuated--relative to the same stimulation produced externally. This is not true, however, for individuals with schizophrenia. Here, we investigate whether the lack of attenuation to self-produced stimuli seen in schizophrenia also occurs for normal participants following REM dreams. Fourteen participants were stimulated on their left palm with a tactile stimulation device which allowed the same stimulus to be generated by the participant or by the experimenter. The level of self-tickling attenuation did not differ between REM and non-REM sleep awakening conditions, where presence or absence of an accompanying dream was not controlled for. However, for the female participants, when awakening occurred from an REM sleep dream, self-stimulation ratings were higher than for external stimulation, whereas ratings after NREM sleep unaccompanied by a dream were lower for self-stimulation than for external stimulation. These results indicate deficits in self-monitoring and a confusion between self- and externally generated stimulation accompany REM dream formation.     

Does mental rotation ability depend on sensory-specific experience?

No study has investigated the link between vision and touch with respect to spatial abilities using a within-subjects design. With this design, we compared participants’ tactile and visual mental rotation abilities, as measured by the Mental Rotations Test (Vandenberg & Kuse, 1978). Participants in four groups completed two consecutive sessions under no-switch (visual-visual or tactile-tactile) or switch conditions (visual-tactile or tactile-visual) to determine whether mental rotation abilities assessed in Session 2 depend on previous sensory-specific experiences (Session 1). Analysis of response accuracy revealed that all groups improved their performance in Session 2. Analysis of response time showed an improvement in visual and tactile performance during Session 2 for participants who first performed the task with the same modality. No effect of task repetition appeared for participants who performed in two different sensory conditions. These results reveal that mental rotation ability partly depends on sensory-specific conditions and that ability developed in a sensory-specific condition does not necessarily transfer to another sensory condition.     

Lateralisation of language and emotion in schizotypal personality: Evidence from dichotic listening

Striking disturbances have been reported in language and emotional prosody processing by patients diagnosed with schizophrenia. In view of this and of research suggesting that schizotypal personality traits can also be expressed sub-clinically, the present study aimed to discover whether similar disturbances would be reflected in cognitive laterality patterns when symptoms of schizotypy are present yet at a non-clinical level. A dichotic listening task was used to examine the sensitivity and speed with which 132 right-handed participants (85 females and 47 males, mean age = 32.44, SD = 12.29) detected both words and emotional prosody, all of whom also completed the Schizotypal Personality Questionnaire. Findings indicated that both high (n = 64) and low (n = 68) schizotypy groups demonstrated the typical right ear advantage for the detection of words and left ear advantage for the detection of emotional prosody. Individuals with higher schizotypal personality scores also demonstrated poorer sensitivity in detecting emotional prosody. These results reveal that within the healthy population, higher levels of schizotypy are not associated with the atypical lateralisation of language and emotion. Nevertheless, the existence of these symptoms does signal the presence of shared characteristics with the clinical sphere, namely poorer emotion recognition performance.     

Older adults demonstrate greater accuracy in joint position matching using self-guided movements

Greater proprioceptive accuracy has been found with active compared to passive movement. Therapeutic approaches in rehabilitation include varying levels of assistance with arm movements. This assistance may impact proprioceptive acuity. Eighteen older adults participated in a joint repositioning study. The ability to independently reproduce a shoulder flexion angle was investigated when the reference angle was set under the following conditions: (1) the examiner actively assisted participant’s motion to the reference angle chosen by the examiner, (2) the participant moved independently, but the examiner provided tactile cueing to stop at the reference angle chosen by the examiner, and (3) the participant independently moved to a self-selected reference angle. Participants were most accurate in the self-guided condition compared to the active assisted or tactile cueing conditions. Both the self-guided and tactilely cued conditions involved active movement, yet accuracy differed. In contrast, there was no difference in accuracy between the active assisted and tactile cueing conditions despite one involving more active movement. The results demonstrate active movement alone does not determine accuracy. External stimuli, either tactile input and/or a reference angle chosen by the examiner may diminish accuracy. This can be clinically relevant as proprioceptive performance has been linked to improved motor performance.