Christopher Cooper

The effect of a low rate of regular signals upon the reaction times of introverts and extraverts

Abstract In an RT (reaction time) task involving responding to infrequent, regular signals, extraverts produced higher proportions of missed signals and lengthened RTs than introverts did. This result was only obtained after some time on task and is evidence that inhibitory states are formed more rapidly in extraverted subjects under low stimulation conditions. In a more extended version of the task, mean RT was found to be longer in extraverted than introverted subjects in the second half of the experiment though there was no significant difference between the groups in the first half. These findings are complementary to data from previous studies showing that extraverts generate stronger inhibitory potential in continuous responding tasks, or that their characteristic arousal level may be lower than that of introverted subjects. The need to distinguish between the different explanatory constructs is discussed and a simple model amalgamating the major theoretical positions is outlined.

Stimulus- or response-induced excitation. A comparison of the behavior of introverts and extraverts

Abstract The tendency to inspect visual material (slides) rather than to respond by pressing a key in an attempt to move on to the next slide, was compared among introverts and extraverts. As predicted from Brebner and Cooper (1974) : (1) extraverts inspected the stimuli for a shorter time before making their first response, (2) extraverts made more responses at a faster rate than introverts did, and (3) extraverts produced a significantly higher proportion of runs of accelerating responses.

Evoked brain potentials, string length and intelligence

Past studies relating electrical brain activity to measures of intelligence have shown widely disparate results. More recently, Blinkhorn & Hendrickson (Nature, 295, 596–597, 1982) and Hendrickson (Parts I and II. In Eysenck, H.J. (Ed.), A model for intelligence. New York, Springer, 1982) have reported high correlations between their AEP measure, termed ‘string length’, and psychometric IQ but few studies have satisfactorily replicated these results. The present study examined the relationship between string length and IQ among 20 first year psychology students and found moderate to high correlations (up to 0.86). It also found that the magnitude of these correlations was sensitive to temporal events occurring within the AEP waveform and an analysis of components within the first 250 msec after stimulus onset demonstrated that the AEP waveforms of subjects with high verbal IQ (VIQ) contained significantly more ‘early’ components than those of low VIQ subjects.

Inspection time correlates with general speed of processing but not with fluid ability

Inspection time (IT) has been shown to correlate reliably with putative tests of general intelligence such as Ravens matrices and more strongly with performance IQ than with verbal IQ from the Wechsler scales. A common interpretation of this pattern has been that PIQ and matrices tests are measures of fluid ability (Gf) and therefore that IT provides an index of a biological substrate underpinning individual differences in IQ. Marker tests for five of the constructs described in Gf–Gc theory of cognitive abilities were administered to a sample of 64 adults who also completed IT estimation. IT correlated −0.43 (p<0.001) with a test of general processing speed (Gs) but did not significantly correlate with a test of Gf. Results of partial correlation analysis and factor analysis were not consistent with the proposition that general intelligence depends exclusively or substantially on speed of processing. A sub-sample of 37 subjects completed a second marker test for both Gf and Gs. The correlations with IT were consistent with those obtained for the larger sample. The results are interpreted within a hierarchical model of cognitive ability that incorporates speed of processing at the same level as fluid ability and crystallized ability.

Hemispheric differences in the rates of information processing for simple non-verbal stimuli

An inspection time task, used to gauge differences in speed of information processing between the hemispheres, was administered to 22 normal subjects. It was found that the left visual field-right hemisphere (LVF-RH) exhibited an inferior performance relative to the right visual field-left hemisphere (RVF-LH). These results were consistent with other studies which have found an RVF-LH advantage for the processing of temporal/serial information. The possible ramifications of these results for models of asymmetry which do and do not attribute the left hemispheres preferential capacity for language to these fundamental processes are then discussed.

Event-related potential correlates of some human cognitive ability constructs

Abstract Event-related brain potentials arguably provide evidence for a relationship between intelligence and low-level brain processes based, at least partially, on physiological speed. Hierarchical models of cognitive abilities (e.g., Gf–Gc theory) describe constructs at different levels of complexity of information processing. Such hierarchies place tests of speed of processing at a low level of the information processing hierarchy [although, in factor analytic terms, general processing speed (Gs) is located at the same level as other general abilities]. The question arises: can a differential pattern of relationships between ERP latencies and cognitive abilities be discerned? Tests from the Woodcock–Johnson Psycho-Educational Battery Revised (an operationalisation of Gf–Gc theory) were administered to 64 adults. ERPs were recorded to pattern reversal stimuli and during inspection time (IT) estimation. ERP deflections with latencies from about 70 ms up to about 240 ms were negatively correlated with tests of cognitive abilities. The highest correlations were with a measure of fluid ability, but no differential pattern of correlations was found. The results are consistent with previous research in this area. That is, ERP latencies and tests of cognitive abilities share 10–25% of variance.

Personality factors and inspection time

The measure ‘inspection time’ (IT) has been used in a variety of correlational studies which show that IT and IQ tend to correlate positively (see Brand and Deary, 1982). As Longstreth, Walsh, Alcorn, Szeszulski and Manis (1986, this issue, pp. 643-651) put it, “‘inspection time’, is the latest entry in the sweepstakes contest of predicting intelligence from simple psychophysical or chronometric measurements”. If it is a contest, IT is a late entry compared with more traditional measures like reaction time (RT). In 1895, in the Psychological Review, R. Meade Bathe published the results of an RT study comparing the speed of responding to auditory, visual and tactile stimuli of White Americans, Black Americans and Indian Americans. He did not use any intelligence test, instead he argued that, “in proportion to intellectual advancement there should be, through the law of compensation, a waning in the efficiency of the automatism of the individual”. From this assertion he argued that if White Americans were intellectually superior to Black or Indian Americans this would be reflected in White Americans having longer RTs than the other two groups. This reverses the more usual contention which equates speed with higher intelligence but. as Table 1 shows, he obtained results in line with his contention although the tactile condition does not, in fact, yield a significant F-ratio.

The Rusalov Structure of Temperament Questionnaire (STQ): results from an Australian sample

Abstract Recently, a new temperament inventory [the Rusalov Structure of Temperament Questionnaire (STQ)] has been developed to account for advances in theoretical models of basic central nervous system processes. Rusalov has hypothesized that temperament consists of 8 dimensions; 4 object and 4 subject related interactions. Australian data is presented, suggesting good agreement between the STQ results in the Australian and Russian samples. Generally, internal reliability was adequate for questionnaire responses.

The string measure of the ERP: What does it measure?

The event-related brain potential (ERP) has been investigated extensively inan effort to understand the neurophysiological bases of intelligence. Measures derived from the ERP have been used as indices of intelligence, particularly the string measure of the complexity of the ERP. However, the string measure has been criticised for being non-specific and for being dependent on ERP amplitude. These criticisms were tested by investigating relationships between ERP string measure, ERP amplitude measures, and the ERP power spectrum. It was found that the string measure was non-specific in that it indexes both low and high frequency event-related activity; the string measure is also dependent on ERP amplitude. The string measure is therefore not a valid measure of the ERP. It was concluded that the string measure should be abandoned; human intelligence cannot map in a simple way onto gross measures of scalp-recorded electrocortical activity.

Event related potential correlates of intelligence

Abstract EEG was recorded at Fz, Cz and Pz while 35 participants either listened passively totones or completed an oddball task. Significant positive and negative correlations were foundbetween the ERP string length measure and WAIS-R Performance IQ and Verbal IQ. The mostimportant factors influencing the sign and magnitude of string length by IQ correlations were theexperimental task and the region of the ERP trace used for calculating string length. Othercontributing factors were the electrode site and whether or not the ERP trace was scaled beforecalculating string length. The formula used to calculate string length had little effect. Significantnegative correlations were found between the ERP variance measure and WAIS-R Verbal IQ andFull Scale IQ.