Is Personality Affected by Brain Activity?

PSY 134 Practical Report

Personality

Affected by

Brain

Activity?

Abstract

122 people were tested under a condition of intermediate stimulation in order to determine whether extraverts showed less alpha activity than introverts. The independent variable was personality, i.e. introvert or extravert, and the dependent variable was alpha activity recorded in the brain.

The participant’s personality was determined by means of an EPI (Eysenck Personality Inventory) – a questionnaire, and alpha activity was measured by an EEG recorder under four different conditions:-

Eyes closed
Eyes open whilst performing mental arithmetic
Eyes closed after hyperventilation
Eyes open

The participants were randomly selected, regardless of age, sex and religion. The only pre- requisite was that they were healthy.

The results were recorded and collected as part of a class experiment and show that the sample was fairly evenly divided between introverts and extroverts. They also show that there is a slight difference between the two means from the groups, but a t-test shows that this difference is of little significance. Hence our hypothesis is rejected.

Introduction

This research project was carried out as part of a follow-up experiment with regards to earlier work conducted by Anthony Gale and Eysenck, both of whom researched personality and its effect on the electrical activity carried out by the brain.

It has been proposed that it is the brain that determines our personality, though it is unclear to which part of the brain is responsible. According to Eysenck there are three predominant personality types- extraversion, neuroticism and psychoticism. Pervin (1993) explained that Eysenck and Long (1986) had considerable evidence found in studies of different cultures, which supported the existence of these three dimensions. The one that we have chosen to focus on and study is that of extraversion. There are two aspects of extraversion, an individual who scores quite low on a scale of extraversion is said to be introverted (quiet) whereas someone who scores quite high is considered an extrovert (loud).

It is unclear as to which particular part of the brain is involved in personality; a lot of research has been carried out in order to narrow it down, so to speak. It has been suggested that because in introverts and extroverts are quite different in their respective demeanours (the former is quiet and the latter is more outgoing) the particular areas of the brain concerning levels of arousal may be involved. According to Ryckman (1992) Eysenck believed in his theory that introverts are highly aroused and so are quiet, whereas extraverts are not they are under-aroused and are so more loud and outgoing. As a result of this theory research has been done to measure the levels of arousal of these two groups, and one way in which this is done is by using an electroencephalograph (EEG) to measure electrical activity originating from the occipital lobe. An EEG is typically used to investigate the brain and how it is functioning, and is a non-evasive procedure. The activity that we were most interested in was that of alpha waves. These are important in order to measure the individual’s level of arousal.

Gale has concluded from his research that there is a significant difference between introverts and extraverts levels of arousal, and therefore their levels of alpha activity, under certain conditions. Eysenck (1967) has put forward that ‘extraverts are lower aroused than introverts’ and it is from this and Gale’s conclusions that we base our hypothesis for our practical experiment. However, it is also important to note that Gale has said under certain conditions and these conditions need to be considered and met if the experiment is to be carried out correctly to obtain accurate results. Gale has suggested the concept of intermediate stimulation, which simply means a middle level of stimulation somewhere between the high level that extraverts would thrive under and the low level that introverts would equally thrive under. Gale suggests that the intermediate stimulation condition should be one in which the participant opens and closes their eyes, or has at least one other individual present in the room with them. Gale’s argument for this condition is that neither an introverted nor an extraverted individual is trying to work against the current level of arousal.

With all this previous research in mind we decided to test Eysenck’s theory under Gale’s intermediate level of stimulation using the following hypothesis: -

Under a condition of intermediate stimulation (participant in a room with other people in a relaxed state with eyes closed) extroverts should show less alpha activity than introverts.

METHOD

(i) Design

This practical was carried out in the form of an ex-post facto study. The variables under investigation were personality and alpha activity. The ...

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With all this previous research in mind we decided to test Eysenck’s theory under Gale’s intermediate level of stimulation using the following hypothesis: -

Under a condition of intermediate stimulation (participant in a room with other people in a relaxed state with eyes closed) extroverts should show less alpha activity than introverts.

METHOD

(i) Design

This practical was carried out in the form of an ex-post facto study. The variables under investigation were personality and alpha activity. The independent variable was personality (extravert or introvert) and the dependent variable was alpha activity. Allocating each participant to one of two groups — introvert or extravert — by means of a personality questionnaire (EPI - Eyscnck Personality Inventory), tested personality. The participant simply answered ‘yes’ or no’ to 24 questions, and their responses indicated to what group they belonged. Both groups were tested in the same way; there was no control group or treatment group.

(ii) Participants

In total there were 122 participants in this study, 62 female (50.8%) and 60 male (49.2%) Of this 63 were introverted and 59 were extraverted. The participants were recruited simply by being asked if they would mind taking part in an experiment on behalf of the first year Psychology class. The nature of the experiment was explained before the participant agreed to anything. If they agreed, then they were recruited. It was not pre-decided how many extraverts and introverts there would be — that was only discovered afterwards. The class was divided into pairs and one participant was recruited for each pair.

It is also important to note that the participants had to be healthy, as the experiment involves breathing deeply and quickly. This was the only requirement age, sex and religion were not a factor.

(iii) Materials

There were a number of materials used in this experiment. Personality was determined by the Eysenck Personality Inventory (EPI, Eysenck & Eysenck, 1964). An EEG recorder was used to measure brain activity, or more specifically alpha activity. The BIOPAC system was used and a full list of necessary equipment needed is included in the BIOPAC manual, which can be found in Appendix 1. Three electrodes and leads were required for each participant, and a headband was used to help keep them in place close to the scalp. Electrode gel was also available to help remove the electrodes from the scalp if needed.

(iv) Procedure

Firstly, the pairs of students carrying out the experiment had to decide between themselves who was going to be the director and who was going to he the recorder. The role of the recorder was to simply record all the data on the computer, whilst the director relayed all the instructions to the participant.

After the participant ad been recruited they were taken to the testing cubicle where the experiment was being carried out. The equipment was all set up ready to begin. Details of how to set up the equipment are included and explained in the BIOPAC manual.

The participant was seated and asked to answer the EPI (a 24-question questionnaire designed to test personality. The questions were designed to find out if the participant was an introvert or an extravert and the ‘yes’ or ‘no’ answers indicated this). After the questionnaire was completed, the 3 electrodes were attached to the scalp. The black electrode lead was attached to the ear lobe; the white was attached just above the ear and the red directly above the white. (The positions are illustrated again in the BIOPAC manual). A headband was then placed over the head in order to help keep the electrodes in place, and also to keep them pressed against the scalp with a constant pressure.

With the computer already set up to start the director asked the participant to relax with their eyes closed, and to keep their eyes closed unless told to open them. There was four different segments to be recorded which were as follows -

Eyes closed
Eyes closed whilst performing simple mental arithmetic
Eyes closed whilst recovering from hyperventilation
Eyes open

Once relaxed the recording began. The recorder recorded for 10 seconds then clicked on ‘suspend’. If the data was correct then they moved onto the next segment. The director then gave the participant a mental math problem, whilst they were still relaxed with their eyes closed. The recorder clicks on resume and records for 20 seconds while the problem is being relayed to the participant. The director has explained to the participant beforehand that they are going to he given a mental math problem which is to be worked out in their head with no talking and their eyes remaining closed at all times.

The problem should be no longer than 20 seconds and after this time the recorder again suspends recording and checks that the data is correct before moving onto segment three. If at any time the data collected was incorrect the director simply clicked on ‘redo’ and the segment was repeated. The director now advises the participant to hyperventilate for two minutes i.e. breath deeply in and out quickly, with their eyes still closed. After the two minutes recording resumes for ten seconds and records the participant recovering from hyperventilation. They should not he hyperventilating during recording. Again, if correct, move onto the next and final stage of recording.

The director now asks the participant to open their eyes and continue to relax. Recording is resumed for another ten seconds. Once completed, and checked that it is correct, the recorder clicks on ‘done’ and saves the data. The electrodes are removed from the participant carefully and both the director and the recorder thank him/her for their time and co-operation. The First year Psychology class carried out this experiment collectively. The class was divided into pairs and each pair tested a participant, and the results pooled for analysis.

RESULTS

This section will include various tables in order to illustrate the results, which were collected and also show whether the hypothesis is correct.

Table 1 Showing Measures of Central Tendency For Age and Extraversion

Table 1 shows the minimum and maximum extraversion scores on the EPI for all the participants put together. The lowest score was 1 and the highest score was 22. It also shows the range of age of the participants, with the youngest being 16 and the oldest being 55. The median of extroversion in Table 1 represents the division between introverts and extraverts; those that score higher than 15 are extraverted and those that scored lower are introverted. Likewise the mean of extraversion represents the average scores that the participants obtained.

Table 2 Showing Frequency Count by Extraversion Frequency

Table 2 shows the scores on the EPI by all the participants. The lowest score was 1.00, showing introversion, and the highest score was 22.00, which indicates a high level of extraversion. If the hypothesis is to be accepted then those who scored above 15 on the EPI should show less alpha activity than those who scored less than 15. Table 3 illustrates these results.

Table 3 Shows Mean Scores by Personality Type

By analyzing Table 3 we can see the mean levels of alpha activity from the first segment of data (resting with eyes closed) between introverts and extraverts. The standard deviation is a measure of how the alpha waves of the participants vary round their mean level.

The two groups, introvert and extravert, were determined by a median split procedure. As indicated in Table 1 the median is 15, and so those who scored 15 or more were put into the extravert group and those who scored less than 15 were classified as introverted. The sample sizes were unequal because quite a few people scored exactly 15, as can he seen from Table 2. There is not much of a difference between the two means, but in order to test this difference to see if it is significant we need to carry out an unrelated t-test. The following table illustrates the results found.

Table 4 Shows Independent Sample t-test

The results from Table 4 indicate that the difference between the two means is not significant. This is shown by the fact that the two-tailed significance level is greater than .05 (p>.O5). This means that there is no significant difference in alpha activity between the two personality groups. Therefore we can reject our hypothesis.

DISCUSSION

As can be seen from the previous section the data that was collected does not support the hypothesis. This section will examine some reasons why the hypothesis was not correct in this case. According to previous research by Eysenck (1967) extraverts are significantly lower aroused than introverts. This information would suggest therefore that on an EEG recording extraverts should show less alpha activity than introverts. However, according to our findings this is not necessarily the case. Our results imply that there is not a significant difference between the two groups.

Some possible reasons to consider before totally rejecting the hypothesis are the conditions in which the experiment was carried out, the age of the participant and whether the participant was able to totally relax, for whatever reason. Gale has said in his work that there are certain conditions that introverts would not like to be tested under, and likewise for extraverts. This correlates with Eysencks theory, Pervin (1993:287) describes that research carried out by Eysenck showed “extraverts more often chose to study in library locations that provided external stimulation than did introverts.” Therefore in researching it is an important implication that different environmental designs best fit the needs of introverts and extroverts. What we need to consider is if the intermediate level of stimulation condition was met when the participants were being tested.

Each participant was tested in the same room with a maximum of three other individuals present - the director, recorder and at least one of the tutors who was in charge of the practical. Gale suggests having someone else in the room is enough for intermediate stimulation, but is more than one person perhaps one too many, especially for those at the extreme ends of the extraversion scale?

Another point to consider is the age of the participants. Age was not important in this study, but from the table of results that illustrates the age of the participants (included in Appendix 1), we can see that the majority of participants were aged 18 or 19. In other words it is more than likely that they were first year university students. However the spread of age was quite wide, ranging from 16 years to 55 years. Perhaps it would have been better to restrict this experiment with age requirements, for example only first year university students. But then the problem of mature students also arises, so it would seem that the problem of a wide range ages is set to stay.

Another point for consideration is how do you know if each participant was totally relaxed? It is possible that the nature of the experiment was not hilly explained to the participant, and they were in some way worried about it. It is also possible that the participant had something on their mind and it was not a good day for them to be tested. This could be another factor affecting the results - the fact that both participant and students knew in advance when the experiment was to be carried out. There was time for the participant to ‘prepare’ for it, but also time for them to work themselves up too.

Another point for consideration is the reliability of the equipment that was used. In the experiment the electrodes had to be changed due to inaccurate results being recorded, after a number of tries. This upset could also have affected the results, in causing upset to the participant, hut also in making one question the reliability of the equipment. However it is unlikely that everyone would have experienced problems with the equipment.

It is also worth noting that we are only concentrating on results from the first segment of data and perhaps this is not enough to reach an accurate conclusion about the difference in alpha activity between introverts and extraverts. It is possible that the difference between the two means for any of the other segments was significant, and this needs to be looked into before disproving past research.

One other final point to consider is the questionnaire that was used to distinguish between extraverts and introverts. The participants may have taken too long deliberating over answers, so their true personality was not coming through, and they were maybe answering what they thought they ‘should’ be answering and not how they really felt about each individual question. Hence they were perhaps not truthful with all their answers. Another point about the questionnaires is that it is an old questionnaire. It was used in this study because it has been used in all past research relating to this study, but maybe it is too out-of-date? A suggestion would be to use a more up-to-date questionnaire, as times are changing so are people so I feel that we need to use a questionnaire that is more recent

The conclusions drawn from past research are no longer concrete in light of our findings, as they do not support each other. If this experiment was repeated, perhaps in a different setting, the outcome could differ, therefore agree with the work of Gale and Eysenck.

The only methodological shortcomings from this practical seem to be the reliability of the equipment (electrodes) and the use of an old questionnaire, all of the reasons, which have already been explained. Another idea which could be examined in further experiments to help improve the reliability of the results, would be to compare all the four stages of testing, and also pre-select the participants and make sure they are well-briefed beforehand on the nature of the experiment.

Some ideas that for further research with regards to personality and brain activity include comparing introverts and extraverts when they are asleep, and compare how their sleeping patterns differ over a set period of time. Another suggestion is to look into the other two main personality types - neuroticism and psychoticism - and compare the electrical activity of the two extremes in each type.

In conclusion, there is no significant difference in alpha activity between extraverts and introverts, hence disproving the hypothesis. However more research needs to he done on this topic to confirm our results.

References

Eysenck, H.J. 1967. The biological basis of personality. Springfield Illinois.
Pervin, L.A. (1993). Personality- theory and research. John Wiley & Sons, Inc. United States.
Ryckman, R.M. (1992). Theories of Personality. Wadsworth, Inc. Belmont, California.