Extraversion Introversion

Among the people you know , someone probably fits the following description: i talkative and outgoing, likes meeting new people and going new places, is active, is sometimes impulsive and venturesome, gets bored easily , and hates routine and monotony. Such a person would score as an extravert on an extraversion-introversion questionnaire. See T able 7.1 for items from a popular extraversion-introversion questionnaire—the Eysenck Personality Inventory .

You probably also know someone who is just the opposite, someone who is quiet and withdrawn, who prefers being alone or with a few friends to being in lar ge crowds, who prefers routines and schedules, and who prefers the familiar to the unexpected. Such a person would score in the introverted direction on an extraversion-introversion questionnaire. If you are wondering why introverts and extraverts are so different from

Table 7.1 Items from the Eysenck Personality Questionnaire Extraversion Scale

Extraversión Items_

For every question, circle just one response.

YES

NO

Are you a talkative person?

YES

NO

Are you rather lively?

YES

NO

Can you usually let yourself go and enjoy yourself at a lively party?

YES

NO

Do you enjoy meeting new people?

YES

NO

Do you tend to keep in the background on social occasions? (reversed)

YES

NO

Do you like going out a lot?

YES

NO

Do you prefer reading to meeting people? (reversed)

YES

NO

Do you have many friends?

YES

NO

Would you call yourself happy-go-lucky?

YES

NO

Do you usually take the initiative in making new friends?

YES

NO

Are you mostly quiet when you are with other people? (reversed)

YES

NO

Can you easily get some life into a rather dull party?

YES

NO

Do you like telling jokes and funny stories to your friends?

YES

NO

Do you like mixing with people?

YES

NO

Do you nearly always have a "ready answer" when people talk to you?

YES

NO

Do you like doing things in which you have to act quickly?

YES

NO

Can you get a party going?

YES

NO

Do you like plenty of bustle and excitement around you?

YES

NO

Do other people think of you as very lively?

Scoring directions: reverse your answers to the items marked "reversed"; then count how many questions you endorsed with a "yes." The average college student scores about 11 on this questionnaire.

Source: Eysenck, S. B. G., Eysenck, H. J., & Barrett, P. (1985). A revised version of the Psychoticism scale. Personality & Individual Differences, 6, 21-29.

Scoring directions: reverse your answers to the items marked "reversed"; then count how many questions you endorsed with a "yes." The average college student scores about 11 on this questionnaire.

Source: Eysenck, S. B. G., Eysenck, H. J., & Barrett, P. (1985). A revised version of the Psychoticism scale. Personality & Individual Differences, 6, 21-29.

Are you a talkative person? Do you like mixing with people? Do you like plenty of bustle and excitement around you? Answering "No" to such questions suggests an introverted personality.

Do you like telling jokes and funny stories to your friends? Do you like mixing with people? Can you get a party going? Answering "Yes" to such questions suggests an extravertedpersonality. Interestingly, Eysenck's extraversion-introversion theory is based not on a need to be with people, but rather on a need for arousal and stimulation.

Are you a talkative person? Do you like mixing with people? Do you like plenty of bustle and excitement around you? Answering "No" to such questions suggests an introverted personality.

Do you like telling jokes and funny stories to your friends? Do you like mixing with people? Can you get a party going? Answering "Yes" to such questions suggests an extravertedpersonality. Interestingly, Eysenck's extraversion-introversion theory is based not on a need to be with people, but rather on a need for arousal and stimulation.

each other , physiologically minded personality psychologists have an intriguing explanation: Eysenck's theory.

A classic example of a physiologically based theory of personality was put forward by H. J. Eysenck (1967) in his book The Biological Basis of Personality . Eysenck proposed that introverts are characterized by higher levels of activity in the brain's ascending reticular activating system (ARAS) than are extraverts. The ARAS is a structure in the brainstem thought to control overall cortical arousal. In the 1960s, the ARAS was thought of as a gateway through which nervous stimulation entered the cortex. If the gate was somewhat closed, then the resting arousal level of the cortex would be lower , and if the gate was more open, then the resting arousal level would be higher . Introverts, according to this theory , have higher resting levels of cortical arousal because their ARAS lets in too much stimulation. Introverts engage in introverted behaviors (are quiet and seek low-stimulation settings, such as libraries) because they need to keep their already heightened level of arousal in check. Conversely , extraverts engage in extraverted behaviors because they need to increase their level of arousal (Claridge et al., 1981).

Eysenck also incorporated Hebb' s (1955) notion of "optimal level of arousal" into his theory. By optimal level of arousal, Hebb meant a level that is just right for any given task. For example, imagine going into a final exam in an underaroused stat (e.g., sleepy, tired). Being sleepy and underaroused would be just as bad for your performance as going into the exam in an overaroused state (e.g., extremely anxious and agitated). There is an optimal level of arousal for taking an exam, one in which you are focused, alert, and attentive, but not aroused to the point of anxiety . Figure 7.2 presents a graph of the optimal arousal curve, also known as the Yerkes-Dodson law.

If introverts have a higher baseline level of arousal than extraverts (i.e., level of arousal while at rest), then introverts are above their optimal level of arousal more often than extraverts. According to the theory, the generally overaroused condition of introverts leads them to be more restrained and inhibited. They avoid active social interactions that might aggravate their already overstimulated condition. Extraverts, on the other hand, need to get their arousal level higher and, so, seek out stimulating

Good

Figure 7.2

Optimal arousal curve.

Figure 7.2

Optimal arousal curve.

activities and engage in more unrestrained behaviors. The qualities that typically characterize introverts (e.g., quiet, withdrawn) and extraverts (e.g., outgoing, engaging) are understood to be attempts to regulate arousal downward (in the case of introverts) or upward (in the case of extraverts) to maintain an optimal level of arousal.

In the decades following the publication of Eysenck' s theory, many studies were conducted to test it (see reviews by Eysenck, 1991; Matthews & Gilliland, 1999; and Stelmack, 1990). If it is true that introverts are more cortically aroused than extraverts, then introverts should display enhanced responsiveness on measures of cortical activity , such as the electroencephalogram (EEG), as well as on measures of autonomic nervous system activity, such as electrodermal response. Studies designed to test this hypothesis typically have taken the form of comparing introverts with extraverts on physiological measures gathered under conditions of various degrees of stimulation (Gale, 1986). In conditions where participants were presented with either no stimulation or very mild stimulation, differences between introverts and extraverts turned out to be small or nonexistent. However, in studies that looked at nervous system responsiveness to moderate levels of stimulation, introverts showed larger or faster responses than extraverts, as predicted by Eysenck's theory (Bullock & Gilliland, 1993; Gale, 1983).

The fact that introverts and extraverts are not dif ferent at resting levels, but are different under moderate levels of stimulation, led Eysenck to a revise his arousal theory (Eysenck & Eysenck, 1985). When he first stated his theory in 1967, Eysenck di not distinguish between resting, or baseline, levels of arousal and arousal responses to stimulation. A good deal of evidence now suggests that the real difference between introverts and extraverts lies in their arousability, or arousal response, not in their baseline arousal level. Extraverts and introverts do not dif fer in their level of brain activity while sleeping, for example, or while lying quietly in a darkened room with their eyes shut (Stelmack, 1990). However, when presented with moderate levels of stimulation, introverts show enhanced physiological reactivity , compared with extraverts (Gale, 1987).

Imagine that an introvert and an extravert have to do a monotonous task, such as monitoring a computer display of the operating status of a nuclear power plant. The display does not change much, so the stimulation level is very low , and the situation is rather monotonous and boring. Eysenck's theory would predict that the introvert would remain more alert and perform better in this situation and that the extravert would be relatively underaroused and most likely bored to sleep. However , now imagine an emer gency at the nuclear power plant, with sirens blasting, lights flashing, and people running an shouting. In such a high arousal situation, it is likely that the extravert would perform better, due to the introvert' s tendency toward overarousal in response to stimulation.

Exercise

The Lemon Juice Demonstration: This demonstration is designed to illustrate that introverts are more reactive to stimulation than extraverts. While some teachers have tried this in the classroom, it can be a bit messy and so might best be done as a thought experiment to illustrate the point in individual differences in reactivity. Here is how it would go: Take a double-tipped cotton swab and tie a thread exactly in its center so that it hangs perfectly in balance (i.e., is horizontal). Swallow three times and put one end on your tongue for exactly 20 seconds. After removing the swab, place 4 drops of lemon juice under your tongue. Place the other end of the cotton swab on your tongue for 20 seconds. Remove the swab and let it hang by the thread. If you are an extravert it is likely that the swab will remain horizontal, indicating that you did not react strongly to the lemon juice by producing more saliva. If you are an introvert, it is likely that the swab will no longer balance horizontally and will instead be heavier on the end placed on the tongue following the lemon juice. This would indicate that you produced more saliva in response to the lemon juice. Eysenck conducted a similar experiment (Eysenck & Eysenck, 1967) as did Corcoran, 1964.

An important corollary of the theory is that, when given a choice, extraverts should prefer higher levels of stimulation than do introverts. Indirect evidence supports this prediction. For example, laboratory studies have shown that extraverts will press a button at a higher rate than introverts when the button pressing produces changes in the visual environment (such as change the channel on a TV, change the slide on a projector) (e.g., Brebner & Cooper , 1978). In a more naturalistic study , done in a university library, persons studying in a noisy reading room scored as more extraverted than did students studying in the quieter rooms (Campbell & Hawley , 1982). Findings such as these suggest that, when given a choice, extraverts tend to seek greater levels of stimulation than introverts.

A clever study designed by psychologist Russell Geen (1984) tested the hypothesis that, although introverts should choose lower levels of stimulation than extraverts, these two groups should nevertheless be equivalent in physiological arousal when performing under their chosen levels of stimulation. However , when extraverts are given the level of stimulation chosen by introverts, they should be underaroused and bored and should perform poorly on the task. When introverts are given the level of stimulation chosen by extraverts, they should be overaroused and distressed and perform poorly on the task. The predictions are complex—take a look at this study on pages 218-219, A Closer Look.

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Anxiety and Depression 101

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