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Biomedical subjects

P H Venables

Publications and source records attributed to P H Venables.

At least 19 recordsLinked to original sources
PubMed2000

The content and structure of schizotypy: a study using confirmatory factor analysis.

This study examined the content of subscales within a multidimensional scale of self-reported schizotypy and their subsequent interrelationship by means of confirmatory factor analysis (CFA). Neither single-factor nor four-factor models provided good fits to the data; two-factor and three-factor models showed very good fits. On closer look, the three-factor solution was, overall, marginally the best fit and gave credence to a model with positive schizotypy, negative schizotypy, and social impairment as the factors. This model was in contrast to those that have disorganization as the third factor. In the present study, the subscale of disorganization loaded on the factor of positive schizotypy. The three-factor solution proposed here may be seen as giving support to the structures advocated by Meehl (1962), Strauss et al. (1974), and Lenzenweger et al. (1991).

Adult↗
PubMed2000

Three-factor model of schizotypal personality: invariance across culture, gender, religious affiliation, family adversity, and psychopathology.

Whilst the syndrome approach to schizotypy has recently demonstrated differential correlates of a three-factor model of schizotypal personality, variations in the nature of these factors question a basic assumption of this approach. This study tested competing models of the factor structure of schizotypal personality using the Schizotypal Personality Questionnaire (SPQ) in a sample of 1,201 Mauritians. Factor invariance across gender, ethnicity, family adversity, and religion and across a psychopathologically select group was also assessed. Results suggest that a three-factor model, Cognitive-Perceptual Deficits, Interpersonal Deficits, and Disorganization, underlies individual differences across widely varying groups. Other competing three-factor schizotypal personality models did not fit the data better. It is argued that the three-factor Disorganized model is a well-replicated model of DSM schizotypal personality in community samples but possibly not in some clinical samples.

Adult↗
PubMed1999

Skin-conductance orienting deficits and increased alcoholism in schizotypal criminals.

This study tested the interaction hypothesis that a subgroup of criminals with schizotypal personality would show skin-conductance orienting deficits and increased alcoholism. In a prospective, longitudinal study of alcoholism in 134 males, schizotypy was assessed during adolescence, skin-conductance orienting was assessed at ages 18-20 years, and criminal offending and alcohol abuse were assessed at ages 30-33 years. A significant interaction between schizotypy and criminality indicated that schizotypal criminals were characterized by autonomic orienting deficits. Furthermore, the rate of alcoholism in schizotypal criminals (54.8%) was significantly higher than in criminals (23.8%), schizotypal noncriminals (13.9%), and comparisons (21.7%). It is argued that schizotypal criminals are a relatively distinct group and that prefrontal dysfunction may underlie both orienting deficits and alcoholism in this group.

Acoustic Stimulation↗
PubMed1998

Fearlessness, stimulation-seeking, and large body size at age 3 years as early predispositions to childhood aggression at age 11 years.

BACKGROUND: Previous cross-sectional research in Western societies has linked adolescent stimulation-seeking, fearlessness, and body size to antisocial behavior. However, it is unclear how early in life these factors exert their influence, and nothing is known about their specificity to aggressive behavior per se. This study tests the hypotheses that stimulation-seeking, fearlessness, and increased body size at age 3 years predict aggression at age 11 years. METHODS: Behavioral measures of stimulation-seeking and fearlessness, together with height and weight, were measured at age 3 years and related to ratings of aggression at age 11 years in 1130 male and female Indian and Creole children from the island of Mauritius. RESULTS: Aggressive children at age 11 years were characterized by increased measures of stimulation-seeking, fearlessness, height, and weight at age 3 years. Stimulation-seeking and height were independently related to aggression, whereas the fearlessness-aggression relationship was mediated by height. Large body size at age 3 years but not 11 years was related to increased aggression at age 11 years, indicating a critical period in development for the influence of body size on aggression. CONCLUSIONS: Results (1) implicate large body size, stimulation-seeking, and fearlessness in the development of childhood aggression; (2) suggest that there may be a critical period in development in which biological processes influence later aggression; and (3) highlight the importance of early processes in the etiology of aggression.

Age Factors↗
PubMed1998

Maternal exposure to influenza in pregnancy and electrodermal activity in offspring: a further study from Mauritius.

This study examined the effect of mothers' exposure to the 1957 A2/Singapore influenza virus in the first, second, and third trimesters of pregnancy on the electrodermal activity of their 15-year-old offspring. The epidemic occurred during cold months of the year. The results show that maternal viral (and cold) exposure during all trimesters of pregnancy produced a lower frequency of nonspecific electrodermal responses and diminished responsivity to 75-db and 90-db tones as compared with the offspring of mothers who were not exposed. However, there was a critical effect of second trimester exposure as indicated by an increase in frequency of nonresponses to orienting tones. The findings are compared with those from an earlier study from Mauritius involving 3-year-old children in which the effects of exposure to the 1968 A2/Hong Kong virus were examined and in which the effect of could exposure could be examined separately because viral exposure occurred during the hot months.

Adolescent↗
PubMed1997

Heart rate and skin conductance in behaviorally inhibited Mauritian children.

This study tested predictions that inhibited versus uninhibited children exhibit higher heart rate (HR) and skin conductance (SC) arousal. Mauritian children (N = 1,795) were tested at age 3 and classified as inhibited, middle, or uninhibited on the basis of social behavior. HR level and several SC measures were obtained immediately before or during a tone task. Inhibited children displayed significantly higher HR and SC levels and longer SC latency relative to uninhibited children. Results remained regardless of ethnicity, gender, height, weight, respiratory complaints, or crying behavior. Findings suggest that HR and SC levels may be early indicators of inhibited or uninhibited behavior at age 3 and support the notion of heightened sympathetic reactivity due to limbic arousal in inhibited children.

Arousal↗
PubMed1997

Low resting heart rate at age 3 years predisposes to aggression at age 11 years: evidence from the Mauritius Child Health Project.

OBJECTIVE: Previous studies indicate that low resting heart rate is probably the best-replicated biological correlate of childhood antisocial and aggressive behavior. Nevertheless, there have been few longitudinal tests of this relationship, little control over potential confounds and mediators, and no test of its cross-cultural generalizability. This study tests the hypothesis that low resting heart rate at age 3 years predicts aggression at age 11 years. METHOD: Resting heart rate at age 3 years was assessed in 1,795 male and female children from Mauritius. Aggressive and nonaggressive forms of antisocial behavior were assessed at age 11 years using the Child Behavior Checklist. RESULTS: Aggressive children had lower heart rates than nonaggressive children (p < .001). Conversely, those with low heart rates were more aggressive than those with high heart rates (p < .003). There were no interactions with gender or ethnicity. Evidence was found for specificity of low heart rate to aggressive forms of antisocial behavior. Group differences in heart rate were not attributable to 11 biological, psychological, and psychiatric mediators and confounds. CONCLUSIONS: It is concluded that low resting heart rate, a partly heritable trait reflecting fearlessness and stimulation-seeking, is an important, diagnostically specific, well-replicated, early biological marker for later aggressive behavior.

Aggression↗
PubMed1997

Maternal exposure to influenza and cold in pregnancy and electrodermal activity in offspring: the Mauritius Study.

Data are in conflict concerning whether a mother's exposure to influenza in pregnancy gives rise to an increased probability that her offspring will develop schizophrenia. In Northern Hemisphere studies, exposure to influenza and cold tend to be confounded. The present study, carried out in Mauritius, examines the effect of maternal exposure to the virus and separately to cold on aspects of electrodermal activity that have been shown in other studies to be related to schizophrenia. The findings are that maternal exposure to influenza in the second and third trimesters gives rise to children who at the age of 3 years show electrodermal hyperresponsivity, whereas exposure to cold in the same periods gives rise to children who tend to be hyporesponsive. In both instances, exposure tends to produce lower levels of tonic activity than in those not exposed to the virus or to cold.

Child, Preschool↗
PubMed1996

The effects of age, sex and time of testing on skin conductance activity.

An investigation of the electrodermal activity of 640 subjects was carried out in Mauritius. Results of a balanced factorial design with 5 age groups, sex, season (hot versus cold), time of day of testing (a.m./p.m.), as factors, suggested the need to take account of age and sex in studies using measures of electrodermal activity. However, season and time of day of testing are seen as important mainly in interaction with sex and give rise to the suggestion that females may be more responsive to environmental conditions than men. The results also provide data which show that a rate of electrodermal non-responsivity of about 25% appears to be constant over the age groups of 5-25 years used in the study.

Adolescent↗
PubMed1996

Schizotypy and maternal exposure to influenza and to cold temperature: the Mauritius study.

A topic of current controversy is that maternal exposure to influenza in the 2nd trimester of pregnancy may place the offspring at increased risk for schizophrenia. However, exposure to cold and to influenza may be confounded in existing studies, and case finding and identification may introduce error. Use of measures of schizotypy that are dimensional may be used to overcome some of the difficulties of case identification. Data are derived from the longitudinal study in Mauritius, an island in the southern hemisphere, where, in the case of the 1968-1972 Hong Kong/A2 influenza virus epidemic, influenza and low temperature were not confounded. The results suggest that women's exposure to influenza in pregnancy is associated with an elevation of positive schizotypy scores, whereas exposure to low environmental temperatures is associated with an elevation of anhedonia scores in their offspring.

Adolescent↗
PubMed1995

The stability of inhibited/uninhibited temperament from ages 3 to 11 years in Mauritian children.

Stability of inhibited/uninhibited temperament was assessed using 1,795 Mauritian children tested at ages 3, 8, and 11 years. Children were divided into uninhibited, middle, and inhibited groups at each age based on social behavior. Results indicated that, relative to uninhibited children (1) those inhibited at age 3 obtained larger inhibition scores at age 8 (p < .0001), (2) those inhibited at age 8 obtained larger inhibition scores at age 11 (p < .002), and (3) those remaining inhibited from ages 3 to 8 obtained larger inhibition scores at age 11 (p < .002). Relative to children who changed classification from ages 3 to 8, those remaining inhibited obtained larger inhibition scores (p < .05) and those remaining uninhibited obtained smaller inhibition scores (p < .015) at age 11. Inhibition scores tended to be higher in females by age 11. Results remained regardless of ethnicity. The results provide some support that inhibited/uninhibited temperament remains stable from ages 3 to 8 and may continue to age 11. The results suggest cross-cultural generalizability of these findings with implications regarding the development of anxiety disorders in the Mauritian population.

Anxiety Disorders↗
PubMed1995

High autonomic arousal and electrodermal orienting at age 15 years as protective factors against criminal behavior at age 29 years.

OBJECTIVE: Nothing is known about biological factors that protect a predisposed individual from becoming criminal. This 14-year prospective study tested the hypothesis that antisocial adolescents who desist from crime by age 29 have greater physiological arousal and orienting than antisocial adolescents who become adult criminals. METHOD: Physiological arousal and orienting were measured in 101 unselected 15-year-old male schoolchildren. Of these, 17 antisocial adolescents who desisted from adult crime (desistors) were matched on adolescent antisocial behavior and demographic variables with 17 antisocial adolescents who became criminal by age 29 (criminals), and 17 nonantisocial, noncriminal normal subjects. RESULTS: Desistors had significantly higher electrodermal and cardiovascular arousal and higher electrodermal orienting than the criminal group. CONCLUSIONS: This is the first study to report biological factors that protect against the development of criminal behavior. The findings suggest that individuals predisposed to adult crime by virtue of showing antisocial behavior in adolescence may be protected from committing crime by high levels of autonomic arousal and orienting.

Adolescent↗
PubMed1994

The relationship of sweat gland count to electrodermal activity.

This study assessed whether greater skin conductance activity at the distal versus medial site (Scerbo, Freedman, Raine, Dawson, & Venables, 1992) is attributable to a greater number of active (open) sweat glands at the distal site. The number of sweat glands was measured using the Palmar Sweat Index (PSI). Twenty-four subjects were exposed to 10 auditory stimuli. Electrodes were placed on the fore and middle fingers of each hand, using distal sites on one hand and medial sites on the other. The PSI was measured at the medial and distal phalanges adjacent to the electrode placement sites. The distal site contained more open and total sweat glands. Open gland count had the strongest correlations with skin conductance. Multivariate analyses of covariance revealed that site effects for nonspecific and orienting response frequency and trials to habituation were associated with site differences in open glands. Skin conductance measures and the PSI reveal greater electrodermal activity at the distal site. In addition, the number of open glands may be a useful measure related to electrodermal response frequency when polygraph measurement is unavailable.

Acoustic Stimulation↗
PubMed1994

The structure of schizotypy, its relation to subdiagnoses of schizophrenia and to sex and age.

A growing amount of evidence suggests that the generally accepted division of schizophrenic symptomatology into positive and negative aspects should be extended to include a third major aspect, namely 'disorganization/social impairment'. As schizotypy can be seen as the non-pathological counterpart of schizophrenia, possibly brought about by the same 'schizotaxic' predisposition(s), it might be expected that the multidimensionality of schizotypy would reflect the tripartite structure seen in schizophrenia. Although the data from studies using scales to measure schizotypy do not clearly support this view, this is mainly because of the relative lack of comparability among the scales used in different studies. Results from the present study, which involve the factor analysis of items rather than scales derived from the testing of a large and diverse population of normal subjects, does, however, support the view that measures of schizotypy may be grouped in a parallel way to symptoms shown by populations of schizophrenic subjects. The suggestion may thus be made that the symptom groupings shown by schizophrenics may be seen as primary and not the secondary result of reactions to earlier phases of the illness. The role of sex and age in the determination of scores on schizotypic dimensions is also examined and show that the sex and age differences found in subdiagnostic categories in schizophrenia are reflected in dimensions of schizotypy.

Adolescent↗
PubMed1992

Disorder of attention in individuals with schizotypal personality.

This study was designed to examine disorder of switching attention in normal individuals with schizotypal personality. High scorers on the physical anhedonia (PA) and schizophrenism (SZ) scales of a questionnaire constructed to measure schizotypy were compared with a group of control subjects. A reaction time test was used that required switching attention across or between auditory and visual modalities. It was found that the high PA scores and the high SZ scorers showed a deficit of shifting attention across modalities compared with the control subjects.

Adult↗
PubMed1992

A major effect of recording site on measurement of electrodermal activity.

Although the medial phalanx has been recommended as the preferred site for recording skin conductance activity, a review of articles published in Psychophysiology indicates that a large minority (34%) of studies employ the distal phalanx. Informal observations also suggest that the distal site may be more reactive than the medial site. This study formally tests this observation by recording skin conductance from both medial and distal phalanges. Twenty-four right-handed subjects (12 male, 12 female) were exposed to a series of 10 orienting and defensive stimuli. Electrodes were placed on the fore and middle fingers of each hand, with distal sites used on one hand and medial sites on the other for each subject. Skin conductance amplitudes were 3.5 times larger at distal than medial sites (p less than .002), while skin conductance levels were 2.08 times larger at distal sites (p less than .0005). A significant Site X Stimulus interaction (p less than .025) indicated that the distal site was more sensitive to habituation over trials and to increases in skin conductance amplitudes with increasing stimulus intensity than the medial site. On the basis of these findings it is recommended that distal sites be used in preference to medial sites in the recording of skin conductance activity.

Adult↗
PubMed1991

Autonomic activity.

A review such as this can do no more than provide an indication of the issues involved in using autonomic activity as a means of providing a "window on the brain." Several points arise. One of the most important is that of careful and appropriate use of techniques available. One well-known textbook of experimental psychology published some time ago advocated the use of two dimes applied to the palm of the hand for the measurement of electrodermal activity. It was this sort of recommendation that led to the use of psychophysiological measurement falling into disrepute. As indicated in the second section, it is important to understand fully the peripheral mechanisms involved before measurement of electrodermal activity can be usefully carried out. Appropriate use of silver/silver chloride electrodes and physiologically appropriate levels of saline in the electrolyte medium can lead to accurate and repeatable measurement where artefact is not carelessly introduced. Equally important is the context in which studies are carried out. The psychological invasiveness of the technique is important to recognize, and it is here that measurement of autonomic activity probably scores over other methods that are available insofar as very little restriction of the subject is required and the number of transducers that must be applied is minimal. The measurement of autonomic activity within the totality of the experimental context is all important. As an example Dawson and Schell investigated the SCR to words which had previously been associated with shock. When these words were presented to the ear to which attention was not directed in a dichotic listening paradigm, an SCR could be elicited although the subject was unaware of the presentation of the stimulus. The importance of the Dawson and Schell study was the care that they took to make sure that the subject really was unaware of the critical stimulus and had not momentarily switched attention from the attended ear. More important, their experiment, in contrast to some which had gone before, used a balanced design in which the critical stimuli were presented on different occasions to each ear. As a result of this it was found that critical stimuli, which were presented to the left ear, right hemisphere, gave rise to SCRs, even when the subject was not aware of their presentation, whereas stimuli presented to the right ear, left hemisphere elicited no response.(ABSTRACT TRUNCATED AT 400 WORDS)

Autonomic Nervous System↗