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The relationship between intelligence, personality and inspection time.

There are two main aims of the present study: first, to examine the relationship between psychometric intelligence (IQ) and personality and to evaluate the Robinson (1989) hypothesis linking different levels of extraversion (derived from the Eysenck Personality Questionnaire (EPQ)) to IQ test performance. Second, to address the Howe (1990) hypothesis that IT and IQ are related because of personality and temperament variables. Each topic will be introduced in turn.

Personality and IQ

Although several authors have discussed this relationship, there appears still to be little consensus. In one of the largest studies to date, Eysenck (1971) has reported that in 398 male nurses extraversion, neuroticism and psychoticism did not significantly correlate with either the Raven's Progressive Matrices (RPM) or the Mill Hill Vocabulary Test. However, it should be noted that one of the problems in searching for correlations between personality and intelligence measures is the fact that, even within intelligence testing, many tests may only share 30-40 per cent common variance when correlated. For example, the correlation between the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the Raven's Advance Progressive Matrices (APM) is usually only around the .5 mark, so that even if a personality dimension does not correlate with one particular test of intelligence it may still correlate significantly with another test (Brebner & Stough, 1994). Obviously the best approach is to correlate a range of tests where practicable; both the WAIS-R and APM have been used for this reason in the present study.

In earlier work Eysenck & Cookson (1969) proposed that a positive association exists for extraversion and intelligence in primary schoolchildren. This association, however, reverses during development so that at secondary school a negative correlation exists. Presumably in adulthood this relationship has disappeared. As recently discussed by Zneider (1994), there are several alternative explanations for this finding. For instance, it may be the case that with increasing education more intelligent students become more introverted while less intelligent students become more extraverted with time. Anthony (1973) has provided some confirmation for this view. Other suggestions by Anthony have suggested that introverts and extraverts develop at different rates around a peak of about 14 years of age.

Saklofske (1985) has provided support for Eysenck's position of no association between personality and IQ. Employing the Kaufman Assessment Battery for Children, the Woodcock-Johnson Brief Scale and the Junior version of the Eysenck Personality Questionnaire (JEPQ) in 105 eight- to 10-year-olds, he reported no significant differences between any of the JEPQ dimensions and performance on the IQ tests. Against these findings are studies by Lynn, Hampson & Magee (1982) and by Crookes, Pearson, Francis & Carter (1981). In the first study, Lynn et al. (1982) correlated extraversion and IQ among 711 adolescents in Northern Ireland. Correlations ranged from .19 for girls and .21 for boys, accounting for small but significant parts of the variance. Crookes et al. (1981) also reported a positive correlation between IQ and extraversion in 15-16-year-old boys and girls.

In the other main theoretical position, Robinson (1982a, b, 1983, 1985, 1986) has discussed extraversion-introversion (E-I) differences in relation to performance on intelligence tests and has proposed that introverts may perform better on tasks requiring verbal intelligence, whereas extraverts may perform better on tasks requiring performance intelligence. In this model it is hypothesized that introverts inherit a nervous system which facilitates the formation of learned connections between stimulus and response. For introverts, any stimulus is associated with greater numbers of learned connections. In addition, Robinson proposes that, in introverts, these learned connections are more quickly accessed, which leads to the development of greater verbal skills than in extraverts. This advantage, however, comes at some cost as the introvert nervous system, because of its greater degree of tonic arousal, forms stronger inhibition of the brain stem system. The brain stem system is hypothesized to be involved in motor sequence processes so that across time introverts will also develop decrements in motor performance skills relative to extraverts. Thus, Robinson has proposed that extraverts will be superior to introverts on intelligence tests measuring performance ability and inferior to introverts on intelligence tests measuring verbal ability. Robinson (1985), in partial support of this theory, has provided evidence that extraversion differences are associated with different intellectual styles but not to absolute levels on intelligence tests, so that differences were not observed in overall IQ but instead in terms of test profile. Saklofske & Kostura (1990) have tested Robinson's predictions in a sample of 84 children who were divided into three groups: extraversion, ambiversion and introversion. All children completed the JEPQ and the WISC-R. Analysis of variance revealed no significant differences on any measure of WISC-R IQ (including verbal and personality IQ) for the three groups, a finding which Saklofske & Kostura interpreted as supporting Eysenck's position that personality and intelligence are unrelated.

More recently Robinson (1989) has proposed a novel model of the neurophysiological basis of intelligence in which previous linear models are replaced with a curvilinear model, linking electroencephalographic parameters to intelligence at different levels of arousal. Linking behavioural data on the relationship between performance on cognitive tests and different levels of arousal (e.g. Corcoran, 1972), he has suggested that the neurophysiological processes underlying the development of intelligence are best when operating at a moderate level of arousal. Robinson equates arousal level directly with Eysenck's conception of extraversion; extraverts are less aroused than introverts at resting level. He has concluded that an intermediate level of arousal is optimal for neural transmission of information. Correlations between measures of mental speed (specifically IT and reaction time (RT)) and intelligence do not reflect a simple serial information-processing-IQ relationship, but instead a trade off between the time taken to access internally stored information and the time taken to extract information from the stimulus that is not previously stored. At this stage, however, this hypothesis is basically untested. Robinson's theory offers a clear hypothesis to test; ambiverts (intermediate resting arousal levels) will record significantly better IQs.

Recently Zneider (1994) has reviewed the relationship between several personality traits and intelligence and has concluded that only modest relationships exist between a wide variety of personality traits and intelligence test performance. As Zneider (1994, pp. 27-28) states: 'The body of research in this area is largely descriptive/correlational, often inconsistent and contradictory, and not easily interpreted or integrated...'. Zneider does acknowledge, though, that with a more refined conceptualization and methodology this conclusion may need to be withdrawn in the future. In order to examine the relationship between personality and temperament dimensions and IQ test performance, WAIS-R, APM, EPQ and the Strelau Temperament Inventory (STI) were administered in the present study.

Personality, IT and IQ

Over the last decade, evidence has been accumulating for a significant relationship between performance on elementary information-processing tasks (IT and RT) and performance on intelligence tests (Brand & Deary, 1982; Jensen, 1982, 1987; Nettelbeck, 1987; Vernon, 1990). At first glance the relationship is a curious one because the chronometric and psychometric measures appear to be measuring different types of performance. Information-processing tasks are non-verbal and involve little knowledge content and attempt to measure an individual's capacity to make threshold-level discriminations, or deal quickly with information in tasks involving choice. IQ tests usually involve the manipulation of symbols, and the perception of relationships, and may demand significant amounts of knowledge. The correlation between these two measures has led some researchers (e.g. Vernon, 1990) to postulate that the development of intelligence may be best understood in terms of elementary indices of nervous system functioning thought to underlie performance on the elementary information-processing tasks. The implications of correlations between these elementary cognitive tasks and IQ are significant for both a theory of intelligence and for the practical assessment of intelligence. For instance, Lehrl & Fischer (1990) have suggested that intelligence may be reconstructed as a scientific theory by employing IT and RT, and Matarazzo (1992) has proposed that by the end of the 20th century intelligence testing will be both psychometric and biological, both authors referring to these elementary information-processing measures.

However, although speed of information-processing measures may correlate with IQ, correlation does not imply causation and there may be other variables that mediate speed-IQ correlations. Along this line, Howe (1990, p. 492) has recently raised an alternative explanation for correlations between speed of information processing and intelligence:

There will be additional reasons for a person's scores at different tasks being correlated whenever, as often happens, a person exhibits attributes of personality or temperament that similarly affect that individual's performance on each of a number of different tasks .... As a result, a person's scores at the different tasks will tend to be correlated, a fact which may be mistakenly taken to be evidence of the presence of general ability or intelligence.

The possibility raised by Howe, that speed of information-processing measures correlate with IQ because of personality or temperament dimensions, is important. The link between intelligence and the performance measures may reflect the efficiency of biological processes or be mediated via cognitive strategies, either of which may relate to personality or temperament. The possibility that an individual's score on speed and IQ measures are correlated because of personality or temperament variables is empirically examined in this study. The speed measure employed in this study is IT, which refers to the minimum amount of time required to make near error-free decisions about a simple sensory stimulus. IT is the shortest duration of presentation at which a person can reliably detect a difference between two stimuli or two features of one stimulus at a selected criterion level (Vickers, Nettelbeck & Willson, 1972). The choice of personality and temperament variables is difficult because Howe (1990) did not define personality or temperament in order for a testable hypothesis relating to personality, temperament, intelligence and IT to be formulated. Therefore, we have employed two major tests of personality and temperament: EPQ and STI. This study represents the first systematic attempt to measure the effects of personality and temperament dimensions on the IT-IQ relationship.

Method

Participants

Sixty-eight first-year psychology students (50 females and 18 males) were tested. Mean age was 18.1 years (SD = 2.0) with a range of ages from 17 to 28 years. Subjects' participation in this experiment formed part of a three-year research project in which several variables were collected to assess the relationship between IQ, personality, temperament, EEG parameters and speed of information-processing variables. One aspect of this work has been reported by Stough, Nettelbeck & Cooper (1992).

Procedure

Psychometric. Subjects participated on a voluntary basis, attending one IT session, one or two sessions for the administration of the WAIS-R and one session for the administration of the personality tests (EPQ and STI). Sixty-four of the total number of students had previously participated in a group testing session in which APM had been administered. The order of the IT, IQ and personality sessions was balanced.

IT. The IT procedure is summarized in Fig. 1. Instructions for the IT task emphasized that the procedure involved accurate, and not rapid, responding. Subjects were told that the task involved simple visual discriminations in which they were required to judge which one of two lines was the shortest. They were instructed that if during the task they became fired they should take a break and then resume. A cue was presented for 500 ms prior to stimulus onset. Subjects were given 10 practice trials at both 200 and 100 ms duration. Subjects were also tested for visual acuity with the Schnellan eye chart and those with poor visual acuity omitted from further participation in the research project. Seven subjects were omitted for this reason. Following the presentation of the cue, the stimulus was presented for a variable duration, ranging from 1 ms to 200 ms and then followed by a mask. The inter-stimulus interval was two seconds. A PEST procedure (Taylor & Creelman, 1967) was used to vary stimulus duration across trials and subsequently to determine each subject's IT score at the 90 per cent level of accuracy. The initial stimulus duration was 100 ms for all subjects and eight reversals were required before an IT estimate could be made. The stimuli and mask were presented via a four-field Gerbrands tachistoscope driven by an IBM compatible computer (AT) which also registered responses made by pressing one of two buttons for either left or right, under the index finger of both hands.

Description of personality and temperament measures

The EPQ (Eysenck & Eysenck, 1975) measures three personality dimensions, Extraversion-introversion (E), Neuroticism (N) and Psychoticism (P). The STI (Strelau, 1987) contains four dimensions, Strength of Excitation (Ex), Strength of Inhibition (In), Balance (B) and Mobility (M), which are all aimed at identifying temperament dimensions based on Pavlovian principles. Strength of Excitation refers to the level of excitation created by stimuli of a given intensity, with greater excitatory strength indicating the nervous system's greater capacity to withstand strong and/or prolonged excitation (Strelau, 1987). Strength of Inhibition describes the processes involved in the ability to maintain a state of conditioned inhibition of which extinction and delay are examples. Balance refers to the ratio between strength of excitation and strength of inhibition, representing the ability of the nervous system to adapt to changes in the environment. Mobility is the capacity to switch between excitatory and inhibitory states (Strelau, 1987).

Results and discussion

Personality and IQ

Table 1 presents means and standard deviations of the personality and temperament variables. All scores fall within the normal range of scores for these tests.

Table 2 displays Pearson correlations between VIQ, PIQ and Full Scale IQ (FSIQ) from the WAIS-R, APM raw scores and the STI and EPQ personality dimensions. There were three main sets of correlations between variables in Table 2. First, VIQ and APM raw scores were significantly correlated to social desirability (L scores) from the EPQ, indicating that subjects with lower VIQ and APM scores are more likely to fake EPQ responses. This finding is consistent with previous research and has been discussed previously (e.g. Eysenck & Eysenck, 1991). Second, strength of excitation from the STI was significantly correlated with IQ (positively) and IT negatively, indicating a role for a Pavlovian theory of arousability in both IQ test and IT performance. Although a small effect, this is an important finding because it suggests that a more specific analysis of the relationship between different levels of arousal and IQ test performance should be undertaken; this analysis is discussed later. Third, there was a small positive correlation between mobility from the STI and the IQ measures. As Brebner & Stough (1994) have explained, Mobility scores are positively related to IQ tasks which are timed and this supports Strelau's (1977) view that temperament traits may be expressed in the dynamics of intellectual processes, referring to the importance of speed of mental processes, and the dynamics of mental activation. In his model, both the efficiency and quality of thought processes are influenced by intellectual abilities. Along these lines, Kozcielak (1979) has compared inventors and non-inventors on tests of intellectual ability and creativity and STI dimensions and has shown that the inventor group scored significantly higher than the non-inventor group on both inhibition and mobility dimensions from the STI, and on the intellectual ability and flexibility tests. Results from Table 2 provide some support for this finding, linking intellectual ability and quickness of mental activation. Apart from these correlations, it appears then that there is little relationship between different measures of IQ, IT and the personality and temperament dimensions.
Table 1. Scores for personality and temperament dimensions

               Mean    SD       Range

Personality

Extraversion   14.4    4.9      2-21
Neuroticism    12.1    5.1      1-23
Psychoticism    4.1    3.2      0-16
Lie             6.9    3.9      1-19

Temperament

Excitation     53.8   10.3     26-78
Inhibition     60.5   11.3     32-82
Mobility       56.8    9.7     29-82
Balance          .94    .27   .52-1.8




[TABULAR DATA FOR TABLE 2 OMITTED]

(Correlations between IQ subtests, IT and personality dimensions)
Table 3. Scores on IQ tests for introverts, ambiverts and
extraverts

IQ test   Introverts    Ambiverts   Extraverts

VIQ            110          117         111
PIQ            108          119         113
FSIQ           109          120         112
APM             25           27          25


Robinson's hypothesis

Robinson has hypothesized that an inverted U function exists between IQ and extraversion so that an IQ advantage exists for ambiverts compared to either introverts or extraverts. In order to examine whether such a function exists, subjects were divided into three groups on the basis of extraversion; extraverts with scores ranging from 17-21 (N = 27); ambiverts with scores ranging from 12-16 (N = 20); and introvert with scores ranging from 2-11 (N = 20). 'Planned comparisons revealed significant IQ score advantage for ambiverts compared to the extravert and introvert groups: VIQ (t = 1.8, p [less than] .05); PIQ (t = 1.9, p [less than] .05); FSIQ (t = 2.3, p [less than] .01); APM (t = 1.7, p [less than] .05). IT scores were not significantly different across the three groups (t = .3, n.s.). Mean scores are reported in Table 3 which suggest that ambiverts may demonstrate modest IQ score superiority over both extraverts and introverts. According to Robinson (1989), this superiority is due to differences in arousal across the three groups, with ambiverts possessing an optimal level of arousal for performance on intellectual tasks. The present results indicate that, at least for performance on IQ tests, ambiverts demonstrate significantly better performance than both extraverts and introverts. Assuming that this difference is related to central nervous system (CNS) arousal level, then the educational significance of this finding is important. If replicated, this finding suggests that there may be an optimal level of CNS arousal for learning and performance in tasks requiring intelligence and that this optimal level may be measured by the extraversion dimension. Intellectual performance may be enhanced in subjects if arousal levels are manipulated to some optimal level. The finding that ambiverts demonstrated an advantage relative to extraverts and introverts for IQ test performance but not for IT performance is surprising, given the correlation between IT and IQ in this sample. This result may be explained in terms of Gale's (1983) position that one should measure arousal levels in the context of the arousing conditions of the task and has suggested that both extraverts and introverts will attempt to increase and decrease their arousal levels to a level in which performance is optimal. According to the theory, it might be hypothesized that for the IT task extraverts and introverts are able to modulate their arousal level so that all subjects perform at a moderate arousal level. Thus no differences in performance are detected. Whether this is true or not will await the results of an experiment that measures arousal level across tasks differing in complexity for introverts, extraverts and ambiverts.

Howe (1989), IT and IQ

Table 4 reports the distribution of VIQ, PIQ, FSIQ, APM and IT scores. Scores on the WAIS-R were approximately one standard deviation above the population average and were also moderately restricted in range, with VIQ recording the greatest restriction in range.
Table 4. Means, SDs and range of VIQ, PIQ, FSIQ, APM and IT scores

Mean               SD    Range

VIQ                113   10.8    88-137
PIQ                114   13.5    86-133
FSIQ               115   11.6    87-138
APM (raw scores)    26    3.7    11-33
IT (ms)             61   25.7    21-136

Note. No adequate norms are available for the APM test.
Table 5. Correlations between IT, VIQ, PIQ, FSIQ and APM scores
(lower figures denote correlations corrected for restriction in
range of WAIS-R scores)

         VIQ          PIQ        FSIQ        APM

IT     -.17       -.40(***)   -.33(**)    -.24(*)
       -.34(**)   -.44(***)   -.48(***)     N/A

VIQ                .45(***)    .87(***)    .41(***)
                   .57(***)    .92(***)    .56(***)

PIQ                            .80(***)    .38(**)
                               .83(***)    .42(***)

FSIQ                                       .47(***)
                                           .57(***)

* p [less than] .05; ** p [less than] .01; *** p [less than] .001.


Table 5 displays Pearson correlations between the IT scores and VIQ, PIQ, FSIQ and APM scores.

When corrected for restriction in range the correlations between IT and PIQ account for about 25 per cent of the IT-PIQ variance, which is the figure proposed by Nettelbeck (1987) as the 'bench-mark' estimate of the IT-IQ correlation and confirmed by a subsequent meta-analysis (Kranzler & Jensen, 1989). Howe (1989) has criticized this conclusion, suggesting that if those studies with sample sizes of less than 40 are omitted from calculation, then the mean correlation between IT and IQ drops to a minuscule -.15 for adults and -.14 for children. Similarly, Mackintosh (1986) has suggested that past IT and IQ correlations are also highly inflated because of the inclusion of subjects with gross intellectual impairments and which therefore attenuate the 'true' correlation. The results of this experiment, in a sample with no subjects with intellectual impairment and with a sample size exceeding 40, do not support either the Howe (1989) or the Macintosh (1986) view. The magnitude of the correlation suggests that IT may be an important measure for the construct of intelligence if it can be established that other parameters do not influence this correlation (e.g. personality and temperament).

VIQ-IT vs. PIQ-IT correlations

Deary (1993) has recently addressed the problem of whether IT is a correlate of performance or verbal processes. Employing confirmatory factor analyses, he demonstrated moderate loadings for IT on a performance factor, and near zero loadings on both a general factor (principal component) and on a varimax rotated verbal factor. Prior to Deary, no rigorous scientific attempt at addressing the issue of whether IT is more related to PIQ than VIQ measures had been reported and, thus, it has been a difficult issue to resolve. The majority of IT studies prior to Deary have not had adequate power to examine this hypothesis post hoc. In order to test the significance of the difference between correlation coefficients, the formula described by Hotelling (1940) was used. Testing the difference between PIQ-IT and VIQ-IT corrected and uncorrected correlations revealed significant differences: t(64) = 3.8, p [less than] .01 and t(64) = 2.2, p [less than] .05 respectively. The present results therefore confirm the Deary analyses and indicate that there is a significant difference between IT-PIQ and IT-VIQ correlations.

Personality and IT

Personality and IT were generally unrelated, although a small but significant association at the .05 level was observed between strength of excitation and IT suggesting that greater arousability to a stimulus leads to enhanced information processing (shorter ITs) and supports the significant positive relationship between strength of excitation and IQ.

Howe (1990), Personality, IT and IQ

Although there was very little relationship between scores on the personality dimensions and IT, the possibility exists, however, for personality and temperament variables to mediate the relationship reported in Table 5 between IT and IQ. In order to explore this possibility, we calculated partial correlations between IT and IQ from which the effects of personality and temperament components had been removed (Table 6). The results indicate that the IT-IQ correlation reported in Table 5 is not [TABULAR DATA FOR TABLE 6 OMITTED] in any sensible way different after the effects of personality and temperament have been removed. Table 6 clearly establishes that, at least for the EPQ and STI dimensions, personality and temperament do not relate to the association between IT and IQ.

A further check of this relationship was performed in the form of hierarchical multiple linear regression analyses. These analyses were performed in two blocks. In the first block all the personality and temperament variables were entered into the regression equation and, in the second block, IT was entered. The first block examined whether the personality and temperament variables were significant predictors of the dependent variables (VIQ, PIQ, FSIQ and APM raw scores) and the second block examined whether IT predicted performance on the IQ measures independent of all the personality and temperament variables. Both extraversion (T = 3.0, p [less than] .01) and social desirability (T = 3.6, p [less than] .01) were significant predictors of VIQ scores. IT did not significantly predict VIQ. in the PIQ regression, IT (T = -3.1, p [less than] .01) and mobility (T = 1.9, p [less than] .05) were significant and independent predictors. In the FSIQ regression, IT (T = -2.6, p [less than] .01), mobility (T = 2.6, p [less than] .01), extraversion (T = 2.6, p [less than] .01) and social desirability (T = 2.8, p [less than] .01) were significant predictors. Social desirability (T = 2.2, p [less than] .05) and IT (T = 2.0, p [less than! .05) were significant predictors of APM raw scores. The pattern of results suggest that for PIQ, FSIQ and APM, IT was a significant predictor variable independent of the effects of the personality and temperament variables. Subjects who tended to fake responses recorded lower VIQs, FSIQs and APM raw scores than those who did not. Mobility from the STI was a significant predictor of both PIQ and FSIQ scores linking Strelau's concepts of mental dynamics with performance on these two scales of the WAIS-R, presumably due to processes involved in spatial intelligence. The results are suggestive of independent effects of personality and temperament variables on IQ test performance. Although many of the correlations between the personality and temperament variables were small, the fact that social desirability, extraversion and mobility were all significant predictors of FSIQ performance is an important step in constructing models of IQ test performance and elucidating biological mechanisms which are central to both the personality (e.g. arousal) and IQ test performance.

As personality and temperament variables were not responsible for the correlation between IT and IQ reported in Table 5, we reject Howe's (1990) hypothesis. Although some authors may wish to conjecture that IT performance may be related to unspecified strategy use or other mediating variables (e.g. Ceci, 1990; Howe, 1990; Mackintosh, 1981, 1986; Sternberg, 1984) and that correlation does not infer causation (Howe, 1990; Macintosh, 1981, 1986), we believe that this approach will not lead to the generation of testable hypotheses. Further advancement in our understanding of the relationship between IT and IQ will clearly not proceed until hypotheses are formulated and tested.

GENERAL DISCUSSION

The present study has addressed a number of issues relating to the relationship between personality, intelligence test performance and IT. The results raise doubts over the validity of the currently held Zeitgeist that considers personality and intelligence to be unrelated. IQ and social desirability, strength of excitation and mobility were all significantly correlated in the present study indicating that future research should address in a more specific manner the relationship between these variables. Whether these correlations indicate the importance of cognitive style and/or biological processes underlying performance on IQ and personality and temperament tests is still to be clearly established. More research is required to define clearly both the cognitive and biological processes underlying social desirability, strength of excitation and mobility. One possible explanation for the significant negative correlations between social desirability and IQ is the selection of the subject sample. University subjects who believe that they performed poorly on the IQ tests and who normally compete for positions in courses may attempt to fake their EPQ responses. The most striking result was the significant IQ advantage demonstrated by ambiverts over extraverts and introverts. The biological mechanism is not known for this relationship although extraversion differences are commonly held to be determined by CNS arousal levels. Thus, within this theoretical framework, ambiverts possess an optimal level of arousal at rest relative to introverts and extraverts which, via unknown processes, results in an IQ advantage. As the biological mechanism for this relationship is far from clearly understood future research should more clearly define the relationship between CNS arousal and performance on cognitive tasks. One possible explanation for this relationship may emerge from psychopharmacological studies. Recent research has demonstrated significant nicotine-related enhancements in elementary cognitive correlates of IQ test performance: RT (Bates, Pellett, Stough & Mangan, 1994), IT (Stough, Mangan, Bates, Frank, Kerkin & Pellett, 1995), and the string-length measure of AEP waveform complexity (Stough, Bates, Mangan & Pellett, in press) and IQ test performance (Stough, Bates, Mangan & Pellett, 1995). The mechanism for this relationship has been postulated to involve the modulation of CNS arousal through cholinergic system activity (Warburton, 1981). If replicated, the practical implications of such a relationship for education are considerable. Tasks may be modified or new tasks invented which optimally arouse students for learning. IQ tests may need to be modified to take into account differences in the arousal levels of introverts, ambiverts and extraverts.

The present study also indicated that IT is a significantly better correlate of PIQ than VIQ, and accounts for about 25 per cent of the PIQ variance. This correlation was not mediated by any personality or temperament variables from either the Eysenck or Strelau personality/temperament tests/inventories. Thus the Howe (1990) hypothesis that IT and IQ are correlated because of personality and temperament variables cannot be supported. Future research should now focus on elucidating the biological processes which contribute to performance on the IT task. As Chaiken & Young (1993) have recently stated, it would appear that IT may be an important and useful measure to assess cognitive performance in a variety of situations in which IQ tests may be inappropriate. Further research may wish to validate IT as a measure of intelligence, using the same procedure that has been used with IQ: correlating performance with measures thought to represent intelligence (e.g. scholastic and occupational success etc.) and which predict performance in a variety of intellectual settings.

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Author:Stough, C.; Brebner, J.; Nettelbeck, T.; Cooper, C.J.; Bates, T.; Mangan, G.L.
Publication:British Journal of Psychology
Date:May 1, 1996
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