The investigation of 3 research hypothesis regarding the EEG / Alpha wave (8-13 Hz)
and extroversion/introversion as measured by the Eysenck Personality Questionnaire (EPQR-A):
Intro:
An abbreviated version of the Eysenck Personality Questionnaire (EPQR-A) developed from
the 48-item short form EPQR was used across four national contexts consisting of four scales
(Extraversion, Neuroticism, Psychoticism and the Lie Scale) of 6 items. It found that
‘reliability and validity of the 6-item scales of the EPQR-A can be recommended as a
functional equivalent to the short form EPQR, when the research context does not adequately
permit the application of the 48-item EPQR-S or the full loo-item EPQR’. (Francis et al.)
Results also showed that THE EPQR-A and the EPQR-S Extraversion, Neuroticism and Lie
Scale reported impressive psychometric properties.
Another study in uncovering the next step of the EEG studies of extraversion-introversion
examined a possible relationship between electrical activity recorded from the scalp and
personality. Results exhibited that ‘extraverts were at least 3 times more likely to have larger
amplitude activity in this range’, (Tran et al.) Posterior regions of the brain showed no
significant associations.
Hypothesis to be tested: Hypothesis 1 – There will be a difference in overall mean alpha
wave amplitude between the eyes open and eyes closed condition for participants who scored
high on Extraversion. Hypothesis 2 – There will be a difference in the overall mean and
amplitude of the alpha wave between participants who scored high on neuroticism and
participants who scored low on neuroticism. Hypothesis 3 – A difference in mean alpha wave
amplitude while performing a mental arithmetic task will be observed between participants
who scored high and participants who scored low on extroversion.
Method:
Design - The type of design used was mixed, combining a within subjects and between
subjects design. The predictor variable is electrode recording. The criterion variable is the
measurement of EEG / alpha waves (8-13 Hz) and extroversion / introversion - EPQR-A of 7
stages 30 seconds each investigating levels of neuroticism and extraversion.
Materials - Biopac student lab: software; acquisition set; electrode lead set; disposable vinyl
electrodes, lyra swim cap. EPQR-A contains 2 items; neuroticism and extraversion which
contains 6 sub-scales. The scale was Yes = 1, No = 0. Scoring was calculated by the sum of
the item scores.
Procedure – Participants were seated in a chair facing away from a computer screen. The
electrodes were positioned on the occipital lobe / ear lobe after moving hair from the
adhesion area. The electrodes were kept on the right side where pressure was applied after
initial placement. The electrical leads were draped over the head to prevent pulling on the
electrodes and a ‘lycra’ swim cap was placed on the participant’s head to press the electrodes
against the head with a constant pressure. The room was reasonably quiet to help the
participant mentally relax. A few minutes were given before starting to record to allow the
participant to settle. The recording phases (each 30 seconds long) included: eyes closed, eyes
open, eyes closed, eyes open, eyes closed, eyes closed and mental arithmetic task – asked to
count back in 7’s from a specified 3 digit number and eyes closed. At the end of each 30
second phase the recorder suspended the recording while giving the instruction for the state
during the next recording. The code number for each participant, the date and the time should
be recorded on the measurement sheet.
Neuroticism contained the sub-scales: Does your mood often go up and down? Do you often
feel ‘fed up’? Would you call yourself a nervous person? Are you a worrier? Do you suffer
from nerves? Do you often feel lonely?
Extraversion contained the sub-scales: Are you a talkative person? Are you rather lively? Can
you easily get some life into a dull party? Do you tend to keep in the background on social
occasions? Are you mostly quiet when you are with other people? Do other people think of
you as being very lively?
Francis, L.J., Brown, L.B. & Philipchalk, R. (1992). The development of an abbreviated form
of the revised Eysenck Personality Questionnaire (EPQR-A): Its use among students in
England, Canada, the USA and Australia. Personality and Individual Differences, 13, 4, 443449.
Tran, Y., Craig, A. & McIsaac, P. (2001). Extraversion-introversion and 8-13 Hz waves in
frontal cortical regions. Personality and Individual Differences, 30, 205-215.