Psychology 3051 Psychology 305A: Theories of Personality Lecture 9 1.

Psychology 305 1

Psychology 305A: Theories of Personality

Lecture 9

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1. Who was Phineas Gage?

The Biological Perspective

2. What physiological measures are commonly used in contemporary personality research?

3. What does contemporary research suggest about the physiological basis of (a) extraversion, (b) sensitivity to reward and punishment, and (c) sensation seeking?

By the end of today’s class, you should be able to:

1. describe contemporary physiological measures used in personality research.

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2. describe Eysenck’s theory of the physiological basis of extraversion.

3. review evidence to support Eysenck’s theory of the physiological basis of extraversion.

5. discuss the roles of the BAS and the BIS in learning.

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6. describe Zuckerman’s theory of the physiological basis of sensation-seeking.

4. distinguish between the BAS and the BIS.

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Who was Phineas Gage?

• Phineas Gage was a 19th century rail worker involved in construction in Vermont.

• In 1848, an accidental explosion blew an iron rod through his head.

• The rod entered under his left cheek and passed through his frontal lobes, ultimately exiting through the top of his

head.

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The Skull of Phineas Gage, 1823 - 18606

Reconstruction of the Path of the Iron Rod Through Gage’s Skull

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• According to Gage's physician, Gage’s personality radically changed after the accident:

Gage was fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was “no longer Gage.” (Harlow, 1848)

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• Neurologist Antonio Damasio has written extensively on Gage. According to Damasio, Gage's story marks the historical beginnings of the scientific study of the physiological basis of personality.

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What physiological measures are commonly used in contemporary personality research?

• Four physiological measures are of particular interest to contemporary personality psychologists:

1. Measures of Electrodermal Activity (Skin Conductance)

Assess the concentration of water or sweat on the palms.

Provide a direct measure sympathetic nervous system activity (i.e., the fight-or-flight response).

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Typically involves placing 2 electrodes on the palm. A low voltage of electricity is sent through one electrode. The electricity detected at the second electrode

assesses how well the skin is conducting electricity.

E.g., Research suggests that people who are high in neuroticism have chronically activated sympathetic nervous systems.

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2. Measures of Cardiovascular Activity

Include measures of blood pressure and heart rate.

Blood pressure and heart rate provide direct measures of sympathetic nervous system activity.

E.g., Research suggests that people who are characterized by impatience, competitiveness, and hostility (i.e., the “Type A” personality) experience chronic cardiac reactivity, which contributes to heart disease.

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3. Measures of Brain Activity

Include positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).

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PET involves administering a radioactive substance attached to glucose to the participant.

The PET scanner detects the emission of positrons from the radioactive substance, thereby indicating where glucose consumption and physiological activity is greatest.

PET Image of the Brain15

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fMRI uses radio waves and magnetic fields to produce an image of physiological activity.

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fMRI identifies regions in the brain where blood vessels are expanded and extra oxygen is being delivered, thereby indicating where physiological activity is greatest.

fMRI Image of the Brain

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E.g., Research employing fMRI suggests that individuals who are high in neuroticism experience increased frontal brain activation when exposed to negative images, whereas individuals who are high in extraversion experience increased frontal brain activation when exposed to positive images.

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4. Biochemical Measures of Blood and Saliva

Assess hormone levels (e.g., testosterone) and enzyme levels (e.g., monoamine oxidase).

E.g., Research suggests that shy children have relatively high levels of cortisol in their systems. Cortisol is a hormone released under stress.

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What does contemporary research suggest about the physiological basis of extraversion?

• Eysenck (1967) proposed a physiological theory for individual differences in extraversion.

• According to Eysenck’s theory, the ascending reticular activating system (ARAS) plays a critical role in

determining levels of extraversion.

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• The ARAS is in the brainstem and controls cortical arousal.

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High levels of ARAS activity result in high levels of cortical arousal.

Low levels of ARAS activity result in low levels of cortical arousal.

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• Eysenck suggested that introverts have relatively high levels of ARAS activity and, therefore, cortical arousal.

• In order to avoid further arousal, introverts restrain themselves, seek low-stimulation settings, and avoid social interactions.

• That is, introverts engage in activities that regulate their levels of arousal downward.

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• In contrast, Eysenck suggested that extraverts have relatively low levels of ARAS activity and, therefore, cortical arousal.

• In order to enhance their levels of arousal, extraverts seek high-stimulation experiences, settings, and social interactions.

• That is, extraverts engage in activities that regulate their levels of arousal upward.

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• Research has provided support for Eysenck’s theory.

E.g., Brebner & Cooper (1978)

Found that extraverts pushed a button at a higher rate than introverts when pushing the button resulted in a change in the visual environment.

E.g., Campbell & Hawley (1982)

Found that extraverts were more likely to study in noisy reading rooms, whereas introverts were more likely to study in quiet reading rooms.

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E.g., Geen (1984) found:

(b) When extraverts were asked to complete the learning task under the noise level preferred by introverts, their performance deteriorated.

(a) Extraverts preferred to undertake a learning task under noisier conditions than introverts.

(c) When introverts were asked to complete the learning task under the noise level preferred by extraverts, their performance deteriorated.

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• More recent research suggests that extraverts and introverts differ in their arousability rather than their baseline levels of cortical arousal (Bullock & Gilliland, 1993; Gale, 1987; Stemlmack, 1990).

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What does contemporary research suggest about the physiological basis of sensitivity to reward and punishment?

• Gray (1972, 1990, 2000) proposed a physiological theory for individual differences in sensitivity to reward and punishment: Reinforcement Sensitivity Theory.

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• Gray’s theory hypothesizes two systems: The behavioural activation system (BAS) and the behavioural inhibition system (BIS).

• The BAS is based in the left prefrontal cortex. The BIS is based in the right prefrontal cortex (DeYoung & Gray, 2009).

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• The BAS is responsive to rewards or incentives, generates positive emotions (e.g., eagerness, excitement), and regulates “approach” behaviours.

• E.g., In a child, the BAS would recognize music emanating from an ice cream truck as a reward cue,

would generate positive emotions in response to that cue, and would create an urge to run to the truck.

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• The BAS is linked to dopamine levels.

• Gray argues that the BAS contributes to individual differences in extraversion or impulsivity (see Davidson, 2003; Knutson & Bhanji, 2006; Pickering et al., 1999).

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• The BIS is responsive to punishment or frustration, generates negative emotions (e.g., anxiety, fear), and regulates “avoidance” behaviours.

• E.g., In a child who is shouting, the BIS would recognize a mother’s stern glance as a punishment

cue, would generate negative emotions in response to that cue, and would inhibit further shouting.

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• The BIS is linked to serotonin levels.

• Gray argues that the BIS contributes to individual differences in neuroticism or anxiety (see Davidson, 2003; Knutson & Bhanji, 2006; Pickering et al., 1999).

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• Gray integrated his theory with learning theory and generated the following hypotheses.

(a) People with a sensitive BAS are more likely to learn when they are rewarded than when they are punished.

(b) People with a sensitive BIS are more likely to learn when they are punished than when they are rewarded.

• Research has provided support for Gray’s hypotheses:

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E.g., Larsen et al. (2003)

• Had participants engage in a learning task.

• Some participants were rewarded for each correct response, earning $5 over the course of the experiment.

• Other participants were punished for each incorrect response; they were given $10 and lost $5 over the course of the experiment.

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• Found that:

(b) participants who obtained high BIS sensitivity scores performed better when they worked to avoid punishment.

(a) participants who obtained high BAS sensitivity scores performed better when they worked for reward.

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What does contemporary research suggest about the physiological basis of sensation seeking?

• Sensation seeking refers to the tendency to seek out varied, novel activities that are both exciting and risky.

• The term “sensation seeking” (SS) was coined by Marvin Zuckerman (1965, 1985, 2005), who developed the Sensation Seeking Scale:

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Examples of Items from the Sensation Seeking Scale

I sometimes like to do things that are a little frightening.

A sensible person avoids activities that are dangerous. *

I like to have new and exciting experiences and sensations even if they are frightening, unconventional, or illegal.

Almost everything enjoyable is illegal or immoral.

I get bored seeing the same old faces.

I like the comfortable familiarity of everyday friends. *

* Reverse-scored items.

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• Zuckerman (1994, 1996; see also Ruchkin et al., 2005) maintains that SS is physiologically based. He found that individuals who were high in SS had relatively low levels of monoamine oxidase (MAO) in their blood.

• MAO is an enzyme that breaks down neurotransmitters.

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MAO breaks down neurotransmitters.

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• Zuckerman maintains that the low levels of MAO in sensation seekers results in relatively high levels of theneurotransmitter dopamine within the nervous system.

• Thus, MAO act as a “brake,” diminishing or inhibitingneurotransmission.

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The high levels of dopamine, in turn, cause a “disinhibition” of the nervous system, resulting in less control over behaviour, thought, and emotion.

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1. Who was Phineas Gage?

The Biological Perspective

2. What physiological measures are commonly used in contemporary personality research?

3. What does contemporary research suggest about the physiological basis of (a) extraversion, (b) sensitivity to reward and punishment, and (c) sensation seeking?