Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
Introversion-extraversion refers to a personality trait that describes the extent to which individuals are outgoing and sociable (extraverted) or reserved and introspective (introverted). It is believed to be rooted in differences in arousal levels.
Arousal levels refer to the amount of physiological activation or energy present in an individual's body and mind. Higher arousal levels are associated with extraversion, while lower arousal levels are linked to introversion.
Eysenck’s Theory: Eysenck’s theory proposes that introversion-extraversion is influenced by biological factors such as cortical arousal levels. He suggests that introverts have higher baseline cortical arousal and therefore seek out quieter environments to avoid overstimulation.
Behavioral Activation System (BAS): The BAS is a brain system responsible for regulating an individual's response to rewards. Eysenck's theory suggests that extraverts have a more active BAS, leading them to seek out stimulating experiences and social interactions.