Chapter 7 provides an introduction to physiological approaches to personality, including discussions of measurement issues, and historical and recent theory and research.

The authors begin with an overview of Sheldon's research and theory on body type as a cause of individual differences. Although much of this work has not been replicated, it is important because it is one of the first research programs to integrate physiology (body type) with personality.

Next, the authors discuss the most common physiological measures used in personality research today, including electrodermal activity, cardiovascular activity, brain electrical activity, and chemical analyses of blood and saliva. Following this review of physiological measures, the authors discuss key physiologically based personality dimensions. They begin with a discussion of Eysenck's theory and research on Extraversion-Introversion, and then present Gray's competing theory and associated research. Next, the authors review theory and work on sensation seeking, introduced by Zuckerman, who relied in part on Hebb's theory of optimal level of arousal.

The authors then briefly review work on the relationships between three neurotransmitters (dopamine, serotonin, and norepinepherine), and follow with a discussion of theory and research on Cloninger's Tridimensional Personality Model, which highlights neurotransmitter-personality relationships. The authors then present theory and research on morningness-eveningness, including work suggesting that individual differences in this trait are attributable to variation in circadian rhythms. Finally, the authors review recent work suggesting that brain asymmetry may predict differences in affective style.