Hans Eysenck's Two-Dimensional Model Theory and William Sheldon's Theory on Somatotypes ($1) Introduction Hans J. Eysenck (1916-1997) was a European psychologist who was the first to study person ...

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Hans Eysenck's Two-Dimensional Model Theory and William Sheldon's Theory on Somatotypes ($1)
Introduction
Hans J. Eysenck (1916-1997) was a European psychologist who was the first to study personality using a method known as factor analysis. He maintained that one's personality can he understood in terms of only two basic dimensions, these are the Introversion-extroversion and stability-Instability (neurotism) dimensions. Eysenck suggested a biological basis for personality traits as he linked introversion-extroversion and stability-instability to differences in individual's normal pattern of arousal within the brain.
Introversion-extraversion
This refers to the degree to which people are inwardly or outwardly oriented. It also reflects the person's level of arousal. For example, Eysenck believed that extreme introverts are chronically over aroused, their brains are too active and they try to minimize stimulation and reduce arousal to get down to the optimal arousal level. Extreme extroverts are chronically under aroused so they need powerful and frequent stimulation to achieve an optimal arousal level or excitation. That is, extroverts seek social contact and physical arousal, like parties and taking chances. They are assertive and suffer boredom easily.
Stability-instability
This dimension represents the suddenness with which arousal occurs or shifts. According to Eysenck, unstable people have nervous systems that show large and sudden shifts in arousal, whereas stable people show smaller and more