Do Physiological Indices of Arousal Correlate with Personality Type - Research Paper Example

Investigation to establish if physiological indices of arousal correlate with personality type Name of Student: Course: University: Investigation to establish if physiological indices of arousal correlate with personality type Abstract The study made an examination of the possible existing relationship between personality and the electrical activity recordings from scalps of people in a sample consisting of fifty three participants. Consequently, the EEG activity in the electrodes was recorded while the participants closed and opened their eyes upon specific instructions. These participants then proceeded to complete the Cattell’s 16 Personality Factor Questionnaire. From the results obtained, personality traits (regarded as second-order traits) were calculated. The traits calculated include subduedness-independence, low anxiety-high anxiety and tough poise-tender mindedness. There was an association established between personality (introversion and extraversion) and the activity in the frontal regions within the 8-13 Hz frequency range. The results revealed that extraverts were thrice likely to possess higher amplitude activity within this range. There were no distinct relationships observed in the brain’s posterior region. Introduction Skin conductance level (SCL) has continued to provide the benchmark for the measurement of tonic modulation of sympathetic activity and also in the indexing of arousal [Mic03]. There was an examination of the effects of methylphenidate stimulant medication on Central Nervous System (CNS), Autonomic Nervous System (ANS) and behavioral measures in children with AD/HD.The discovery made was that SCL happened to be lower in AD/HD children than in the controls, with this difference being ameliorated after stimulant medication. These were factual details used to support the AD/HD hypo arousal model. In another study, with normal children, we found that high and low arousal groups, defined by their resting SCLs, differed in relative alpha level and mean alpha frequency in their concurrent eyes-closed EEG (Barry et al., 2004)[Rob03]. SCL was inversely related to alpha power and directly related to alpha frequency. Compatible data were recently shown in an adult population [Rob05]. These data are compatible with traditional EEG arousal concepts[Rob03], and support the use of SCL as a simple measure of CNS arousal. An inverse relationship between arousal (SCL) and alpha power appears to be a robust finding. Arousal is most often examined over a single group. Individual differences often are not considered. For this lab report one individual difference will be considered – extraversion score, derived from the International Personality Item Pool. Eysenck made a suggestion that biological significance could be the reason to attribute to his unique personality dimensions of neuroticism, psychotism and extraversion since they were based in the first instance on clinical criterion groups. In order to develop markers For the three dimensions, he embarked on the comparison of the neurotics with the rest of the population[Rob03]. Eysenck then then utilized factor analysis in the identification of relevant items for a questionnaire to be used to assess neuroticism and also for the subsequent maximization of the independence of extraversion, psychoticism, and neuroticism. Eysenck, in the year 1967, made advancements on the biological account on neurotic and extraversion he had presented earlier on. The differences in neuroticism were casually linked to the limbic system or visceral brain while those in extraversion were linked to the Ascending Reticular Arousal System (ARAS). Introverts, as opposed to the findings on extroverts, were perceived to possess high ARAS sensitivity and were chronically more cortically aroused[And05]. As opposed to individuals displaying emotional stability, neurotic individuals were perceived to possess rather high limbic system activity that explained their greater autonomic activation. Based on this theory, large volumes of experimental research were generated, all of which had their focus directed towards the significant differences between dysthymics and hysterics. These clinical groups were perceived to have equal highness on neuroticism, but occurred at opposite poles as viewed from the extraversion dimension[Rob08]. The hysterics were more of extraverted and neurotic while dysthymics were seen to be neurotic and introverted. With the focus of the research being shifted to the rest of the population, there was more emphasis on the study of extraversion and relatively lower studies on neuroticism. In the year 1994, Eysenck made an observation that tests on any given biological theories on personality are found at a psychological level. There is little evidence however to support the extraversion-related differences in tonic arousal[Rob03]. Robinson embarked on a mission to build on Eysenck’s work and he was able to come up with the personality theory. Robinson was able to propose two neurological dimensions which account for the existing differences on the extraversion and neuroticism dimensions. The first dimension, which is relative to the thalamocortical excitatory and inhibitory neurons’ effectiveness, was perceived to be the determinant of immediate reactivity to specific stimuli[YTr99]. This dimension provides a basis for a sociability personality dimension that runs between the introverted neurotic (displaying high reactivity) and extraverted stable (displaying lower reactivity). The second dimension that Robinson identified was overall arousability, that was contended to be a function of immediate reactivity and also the extent to which activity occurring in thalamocortical circuits persists after stimulus input is ceased[YTr99]. Hypotheses 1. Over groups, an inverse relationship will be shown between arousal (SCL) and global alpha power. According to the PEN model introverts are characterized by higher levels of activity than extraverts and so are chronically more cortically aroused than extraverts. 2. The Low E group (introverts) will show higher levels of arousal than the High E group (extroverts). 3. An inverse relationship will be shown between arousal and alpha power for the low E group. (High arousal/low alpha) 4. An inverse relationship will be shown between arousal and alpha power for the high E group. (Low arousal/high alpha) Method Participant Fifty three subjects, 44 female (M: 24 years, range 20-59) participated in this research as a means of partially fulfilling course requirements for an undergraduate university subject. Procedure Participants were asked to first complete a demographic and screening questionnaire and the General Health Questionnaire, the Connors adult ADHD rating Scale, the International Personality Item Pool, and the Centre for Epidemiological Studies Depression scale. Only the Extraversion (E) scale from the International Personality Item Pool will be examined for the current study. Subjects participated in several simple auditory tasks. Stimuli consisted of 1000 Hz tones with a duration of 50 ms (15 ms rise/fall times) at 60 or 80 dB intensity presented via headphones. A two minute eyes-closed baseline period was recorded before and after the tasks. Alpha power and SCL from the first two minute eyes-closed baseline period was examined for the current study. Data Extraction SCL was recorded from Ag/AgCl disk electrodes taped on the ventral surfaces of the medial phalanges of digits II and III of the non-dominant hand. An electrolyte of 0.05 M NaCl in an inert ointment base was used, and a constant voltage of 0.5 V was applied across the electrode pair. EEG was continuously recorded from 17 sites (Fz, F3, F4, F7, F8, Cz, C3, C4, T3, T4, T5, T6, Pz, P3, P4, O1 and O2) of the 10-20 system using an electrode cap. All scalp electrodes were referenced to linked ears and a site between Fpz and Fz was used as ground. The vertical electro-oculogram (EOG) was recorded using two tin cup electrodes placed 1 cm above and below the left eye, and horizontal EOG from electrodes placed 1 cm beyond the outer canthus of each eye. All electrode impedances were below 5 KOhm. Signals were amplified (EEG x 20,000, EOG x 5,000) with a band-pass of 0-30 Hz and sampled by a 16 bit A/D converter with a sampling rate of 512 Hz. The EEG data were divided into 2 s epochs. Epochs containing artefacts were rejected, as were the first 5 epochs (to avoid evoked responses to the eyes-close signal). Subjects contributed an average of 45.5 artefact-free epochs (SD = 10.5, minimum = 15). For each subject in each condition, average power spectra were calculated using FFTs with a 10 % Welch window. At each electrode, absolute power in the delta (1.5–3.5 Hz), theta (4-7.5 Hz), alpha (8-13 Hz) and beta (13.5-25 Hz) bands were calculated, as was the weighted mean alpha frequency. Mean SCL was calculated for each participant for the same 2 min period as the EEG. Data Analysis Extraversion scores ranged from 17 to 45 (mean 33). 36 participants were selected for the subsequent analysis, based on whether they scored high E (18 participants: range 38 – 45) or low E (18 participants: range 17-26) on the extraversion scale. SCL and alpha power for each participant is given in the attached excel worksheet. For the first analysis, correlations were obtained for resting SCL and alpha power over all participants in the sample. For the second analysis a between groups ANOVA was conducted, between the high E and the low E groups for arousal level (SCL). For the third analysis multiple correlations were obtained between arousal (SCL) and alpha power for the high E and low E groups. Results 1. An inverse relationship was shown between arousal and alpha power over groups (Pearson correlation, r = -0.40, p < 0.01). The R2 value was 0.16 2. Arousal was higher for the Low E (mean 8.2 mS) than the High E (mean 2.9 mS) group (F (1, 34) = 37.29, p < 0.001). 3. An inverse relationship was shown between arousal and alpha power for the Low E group (Pearson correlation, r = -0.61, p < 0.01). The R2 value was 0.38 4. No significant relationship was shown between arousal and alpha power for the High E group (Pearson correlation, r = 0.25, p > 0.05). The R2 value was 0.06. Charts from the Study Discussion This study was geared towards the further exploration of the existing relationship between personality traits and the EEG activity. The results obtained showed very distinct differences between extraversion and introversion groups with regards to the frontal 8-13 Hz amplitude reactivity. The extraverted people included in this sample were thrice likely to display a higher amplitude within the 8-13 Hz spectrum. On the same note, the introverted people in the sample were expected to display smaller wave levels in this 8-13Hz spectrum. The low arousal levels are hypothetically associated with the higher amplitudes within the 8-13Hz spectrum. The higher arousal levels and EEG waves are conversely associated with the low amplitudes falling in this spectrum. This shows the support for the theory on extraversion, formulated by Eysenck (1967)[Rob05]. The theory makes the proposition that the notable differences between extraverts and introverts are easily distinguishable based on the difference in the cortical arousal levels. This difference in the levels of cortical arousal as seen in extraverts and introverts is perceived as that originating from the difference in the activity level by the Ascending Reticular Activating System (ARAS)[And05]. With the introversion case for instance, the ARAS has its activity serving in the stimulation of their cerebral cortex thus resulting in the higher cortical arousal levels. A proposition by Gray( 1970) states that the introversion’s physiological basis includes a negative feedback loop which involves the frontal cortex, the hippocampus and the medial septal area[Rob05]. The association between personality and the 8-13Hz frequency spectrum in this study was exclusively found in the frontal sites. This is a reiteration of how important the frontal sites in the brain are in personality development. Damage on the frontal lobes can result in the disintegration of one’s personality according to neurological studies [Rob05].In addition to this, damaging the frontal cortex leads to the impairment of cortical arousal. This actually works to support Gray’s proposal on the involvement of frontal lobes as a basis of the different arousal levels for extraverts and the introverts. This study also shows a trend with greater alpha activity levels in extraverts as compared to introverts which are displayed in the posterior regions. This leads to the proposition that there are higher alpha activity level in the scalp of extraverted persons[YTr99]. However, the alpha activity levels are found to be significantly greater in the extraverted persons’ frontal regions. Previous studies have established that there is a relationship between high frequency alpha waves proneness to anxiety [YTr99]. However, this study is not supportive to this relationship as outstanding differences were found in the scalp from the anxiety levels in the 8-13 Hz frequency. Stenberg was able to establish the fact that frontal asymmetry in EEG is distinctly different in low-anxious and high-anxious participants. This however occurred in theta frequency bands. This study established that there is meagre relationship between the levels of anxiety exhibited in introverted and extraverted persons despite the proposal by Gray that introverts are more likely to have higher anxiety levels. Extraversion, which is a secondary trait is a composition of several primary traits. [Mic03]Extraversion is in the 16 PF calculated using 11 primary factors, all of which have different weighting. Factors that have stronger weighting are Self-sufficiency, boldness, dominance and impulsivity[Mic03]. These factors exhibited outstanding differences with the different frontal 8-13 Hz activity levels. On the overall, boldness, impulsivity and higher dominance scores exhibited higher 8-13 Hz activity levels. On the other hand the self-sufficiency levels were opposite, since those with the higher scores exhibiting lower frontal activity in the 8-13n Hz frequency[Rob05]. Discuss limitations associated with this study 1) There was difficulty in the identification of components of the psychophysiological activity. These are the activities that relate to the ARAS’ tonic influence and the thalamocortical systems’ phasic influence. 2) The identification of personality characteristics that are determined by the above components is also difficult. Recommendations for Future Research This study did not support the hypothesis regarding extraverted neurotic persons having lower frequencies of SCL. It is thus a recommendation that results from SCL should be accommodated in the Robinson’s theory, if we are to have this measure conceptualized as a reactivity index. References Mic03: , (Luciano, 2003), Rob03: , (Robert Barry, 2003), Rob05: , (Robert J. Barry, 2005), And05: , (Andre Beauducel, 2005), Rob08: , (Buckingham, 2008), YTr99: , (Y. Tran, 1999), Rob05: , (Robert J. Barry, 2005), YTr99: , (Y. Tran, 1999), Mic03: , (Luciano, 2003), Read More

Eysenck then then utilized factor analysis in the identification of relevant items for a questionnaire to be used to assess neuroticism and also for the subsequent maximization of the independence of extraversion, psychoticism, and neuroticism. Eysenck, in the year 1967, made advancements on the biological account on neurotic and extraversion he had presented earlier on. The differences in neuroticism were casually linked to the limbic system or visceral brain while those in extraversion were linked to the Ascending Reticular Arousal System (ARAS).

Introverts, as opposed to the findings on extroverts, were perceived to possess high ARAS sensitivity and were chronically more cortically aroused[And05]. As opposed to individuals displaying emotional stability, neurotic individuals were perceived to possess rather high limbic system activity that explained their greater autonomic activation. Based on this theory, large volumes of experimental research were generated, all of which had their focus directed towards the significant differences between dysthymics and hysterics.

These clinical groups were perceived to have equal highness on neuroticism, but occurred at opposite poles as viewed from the extraversion dimension[Rob08]. The hysterics were more of extraverted and neurotic while dysthymics were seen to be neurotic and introverted. With the focus of the research being shifted to the rest of the population, there was more emphasis on the study of extraversion and relatively lower studies on neuroticism. In the year 1994, Eysenck made an observation that tests on any given biological theories on personality are found at a psychological level.

There is little evidence however to support the extraversion-related differences in tonic arousal[Rob03]. Robinson embarked on a mission to build on Eysenck’s work and he was able to come up with the personality theory. Robinson was able to propose two neurological dimensions which account for the existing differences on the extraversion and neuroticism dimensions. The first dimension, which is relative to the thalamocortical excitatory and inhibitory neurons’ effectiveness, was perceived to be the determinant of immediate reactivity to specific stimuli[YTr99].

This dimension provides a basis for a sociability personality dimension that runs between the introverted neurotic (displaying high reactivity) and extraverted stable (displaying lower reactivity). The second dimension that Robinson identified was overall arousability, that was contended to be a function of immediate reactivity and also the extent to which activity occurring in thalamocortical circuits persists after stimulus input is ceased[YTr99]. Hypotheses 1. Over groups, an inverse relationship will be shown between arousal (SCL) and global alpha power.

According to the PEN model introverts are characterized by higher levels of activity than extraverts and so are chronically more cortically aroused than extraverts. 2. The Low E group (introverts) will show higher levels of arousal than the High E group (extroverts). 3. An inverse relationship will be shown between arousal and alpha power for the low E group. (High arousal/low alpha) 4. An inverse relationship will be shown between arousal and alpha power for the high E group. (Low arousal/high alpha) Method Participant Fifty three subjects, 44 female (M: 24 years, range 20-59) participated in this research as a means of partially fulfilling course requirements for an undergraduate university subject.

Procedure Participants were asked to first complete a demographic and screening questionnaire and the General Health Questionnaire, the Connors adult ADHD rating Scale, the International Personality Item Pool, and the Centre for Epidemiological Studies Depression scale. Only the Extraversion (E) scale from the International Personality Item Pool will be examined for the current study. Subjects participated in several simple auditory tasks. Stimuli consisted of 1000 Hz tones with a duration of 50 ms (15 ms rise/fall times) at 60 or 80 dB intensity presented via headphones.

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