Investigating the Correlation Between Extraversion and Introversion in Males and Females
This study's aim is to find out if there is any correlation between
extraversion and introversion in males and females, using an Eysenck
personality questionnaire. There were seventy-two participants who
took part in the completion of the questionnaire
. The participants
then completed an EEG experiment to find the measurements of each of
the standard deviation
and frequency levels in the alpha
recording segment. What we expect from our findings is that extroverts
are predicted to have higher amplitude, lower frequency wave than
Although there was seventy-two participants took part in this study, 3
of which were excluded as their gender and age were not recorded.
Another 10 were also excluded as no matching 'alpha-wave' measurements
were found; this left a total sample of 59. We used the Cronbach's
alpha coefficiency reliability scale of .87, whereas the sample number
was 59, the items were 6 and the alpha equalled .8672.
We discovered from the information recorded that the mean score for
extraversion was 3.7 and from this we were able to categorise them
between low and high, with low being <3.7 and the high being â‰¥ 3.7.
We further investigated the study by using a t-test for a statistical
analysis. We wanted to find if the means for SD1, SD2 and SD3 as well
as Freq1, Freq2 and Freq3 vary between those categorized as high and
low on the extraversion. As the findings in Sd2 were
t= -2.084, df = 57, P<.05. Therefore this tells us that there is a
significant difference with this item and the null hypothesis was
rejected as a result.
The investigation we will be carrying out will be focused on the EEG
alpha wave (8-18Hz) in conjunction with extraversion/ introversion and
this is measured by the Eysenck Personality Questionnaire - revised
and abbreviated version (EPQR-A). this study was carried out on a
class of seventy-two psychology students based at the University of
Ulster's Magee campus.
The EEG (8-13Hz) measures the electrical activity of the brain as
transducers and electrodes are placed on the scalp and this records
the electrical signals. The activities of the brainwaves are then
transferred onto the MP30 acquisition of the Biopac student package
through a cable.
The brainwave is exemplified with 20-200uV amplitude and the 8-13Hz
frequency. The maximum amplitude is recorded in the areas of the
occipital and parietal of the cerebral cortex. Readings collected can
differ from each individual. Amplitude and frequency of alpha rhythm
concerning both genders differ slightly, whereas men usually have a
slightly lower reading.
The alpha rhythm changes when participants both open and close their
eyes, when the eyes are opened the participants are aware of stimuli
around them, and this causes the waves to be reduced. However,
amplitudes are greater when the participant has their eyes closed.
Higher amplitudes would be attributed to the more extraverted
personality trait. Through much research a high association between
EEG alpha activity and extraversion may be prevalent. However, a
number of studies have revealed improved activity in introverts.
Eysenck (1970) used factor analysis to construct his theory of
personality in which he recognized extraversion and introversion.
Extraversion refers to an
outgoing trait which have a high level of activity, whereas
introversion refers to the withdrawn and reserved trait. Eysenck
identifies personalities from a biological nature (1991). He argues
that levels of arousal of cerebral cortex are produced by functions of
the neural system which is situated in the brain stem. Extraversion
call for additional external stimulation to maintain the optimum
arousal compared to introversion.
Gale (1981) suggested that conclusions that are compatible could be
due to a range of differences in the population of the study and also
the different techniques used. He also stated that when the extravert
and introvert are learning to become familiarized to their
environments they use many approaches for resolving the inconsistency
among innate levels of arousal and optimum arousal level. The
extravert finds stimulation from external sources by means of
integration and pursues experiences that are greatly stimulating.
Whereas the introvert avoids integration and stimulation which
maintains their low level of arousal at an optimum state.
We will be performing this experiment based on the Eysenck personality
theory to predict if in optimum environmental conditions, extraverts
do have more alpha activity that is higher amplitude, lower frequency
wave than introverts.
The sample we employed to conduct this experiment consisted of
seventy-two University of Ulsterstudents. All of which were of
different race and gender, and all students that participated were of
various age groups.
The investigation that was carried out involved many instruments.
Firstly an Eysenck personality questionnaire was completed by the
seventy-two participants. A Biopac student lab was made use of,
software, acquisition unit; electrode lead set, disposable vinyl
electrodes and a Lycra swim cap were all introduced to provide
readings of brain activity. The results of such activity were then
recorded onto a computer.
We conducted the study using a class of seventy-two psychology
students at Magee campus were they were asked to participate in the
completion of the Eysenck personality questionnaire. The aim of this
was to measure levels of introversion and extraversion between the
participants. They were then asked to take-part in an EEG experiment
and were instructed to place electrodes on the occipital lobe,
parietal lobe and the earlobe and to apply pressure to these.
Electrical leads were then put in place and the Lycra swim cap was
placed on the participants
head to keep a constant pressure on the electrodes. This was to ensure
good contact as it is essential to minimise the noise and to increase
The study contained three segments and involved three participants in
each group. Each individual took it in turn to act as director,
recorder and participant. Segment 1 of the study is were the
participant was asked to close their eyes and relax for 20 seconds, in
segment 2 he was asked to open his eyes without blinking for a further
20 seconds, he was then instructed to close his eyes again for the
final segment. All the data was then recorded. Although there were 3
wavelengths on the screen while recording, we concentrated on the
measurements of standard deviation and frequency in the alpha-wave
The data that was collected during the study was that of nominal and
independent measures, this was then analysed using a descriptive
statistics table to predict the mean score of extraversion which was
calculated to 3.7. These were then categorized into 'Low',
score, and 'high', â‰¥ mean score. We then further investigated with
t-test tables to statistically analyse the means for the SD1, SD2, and
SD3 and Freq1, Freq2 and Freq3, to see if there was any difference on
both categories. The findings concluded that there was a significant
difference so we then rejected the null hypothesis and the hypothesis
was accepted as the results showed in the t-test that item SD2 was
T= -2.084, df = 57 P<.05
As we have seen throughout our experiment our findings revealed that
there was a significant difference on the item SD2, whereas
SD2, t= - 2.084, df= 57 P<.05. So from this prediction we were able
to accept the hypothesis and reject the null hypothesis. Whilst the
hypothesis of the study was to predict that extraverts have more alpha
activity, higher amplitude, lower frequency wave than introverts, we
have found this to be the case in this study.
The outcome of this study could have been proved different for many
reasons, as we have seen that only a small sample was used, as there
were only seventy-two participants. Also the participant may have been
going through some kind of stress or anxiety during the time of the
readings which would result on a contrasting outcome. The timing could
have also been an attribute as different times of the day can affect
people in different ways. The lab that was used to carry out the study
was very small and the participants were in close proximity with each
other and this again may have resulted to the outcome.
There could have been improvements made towards the experiment if a
larger sample of participants were used to complete the study and a
bigger, much quieter lab were the participants were not so much in
close proximity. Also the time of the day could have an effect on the
result as the EEG experiment took place between the hours of 1.30pm
-4.30pm and amplitudes then tend to higher in outgoing and extroverted
Eysenck, H. J., & Eysenck, S. B. G. (1975). Manual of the Eysenck
Personality Questionnaire. (San Diego, CA: EdITS)
Eysenck, Hans Jurgen (1985) Personality and Individual Differences : A
Natural Science Approach. (New York: Plenum Press).
Eysenck, S. B. G., Eysenck, H. J., & Barrett, P. (1985). A revised
version of the psychoticism scale. Personality and Individual
Differences, 6, pp. 21â€‘29.
Eysenck, H. J. (1990). Biological dimensions of personality. In: L.
Pervin (Ed.) Handbook of personality: Theory and research (New York:
The Guilford Press)
Francis, L.J., Brown, L.B. & Philipchalk, R (1992). The development of
an abbreviated form of the revised Eysenck Personality Questionnaire
(EPQA-4): Its use among students in England, Canada, the USA and
Australia. Personality and Individual Differences, 13, 4, 443-449.
Gale, A. (1980) EEG studies of the extraversion-introversion: What's
the next step? In R. Lynn (Ed.) Dimensions of Personality: Papers in
honour of H.J. Eysenck. London: pergamon. (OFFPRINT)
Tran, Y,. Craig, A. & McIssac, P. (2001). Extraversion-introversion
and 8-13 Hz waves in frontal cortical regions. Personality and
Individual Differences, 30, 205-215.