Introduction to Psychophysiology of Human Personality

The analysis of historical data has shown that there have been numerous attempts in exploring and understanding individual differences in human personality. Many of them have been using the arousal construct seemed as the most dominant one. Since then, personality psychology has revealed many personality theories and measurement methods as a theoretical and methodological frame in understanding human personality. Besides that, the same researchers and many others have tried to explain human personality and its various psychological concepts using different psychophysiological methods. Therefore, contemporary psychophysiology of personality includes all research on the biological basis of personality underlying trait-like differences in psychological functioning. This section will provide a detailed overview of the psychophysiology of human personality along with the most intriguing research questions.

Electrophysiology of Human Personality

In this section an overview on evoked brain potentials will be introduced, same as the bases of electrophysiology of the brain. The main research findings on evoked potentials and other psychological variables such as cognition, emotion, motivation and personality will be presented. The emphasis will be given to the relationship between evoked brain potentials and personality operationalized by previously presented two personality theories: Eysenck's and Strelau's theory. Even though it is possible to expect, based on arousal theory, that introverts who had higher sensory reactivity on physical stimuli of moderate intensity and higher levels of cortical arousal than extraverts, would also show higher P300-amplitudes in both modalities, audio and visual, due to other significant variables (i.e. task type, other psychological and physiological characteristics of subjects, etc.) some other results could be expected. Therefore, all complexity about the relationship between evoked brain potentials and human personality and relevant research methodology will be presented here.

Conclusions and Future Research Guidelines

The main aim of this book is to present contemporary research findings in the field of brain activity and human personality. Certain psychological and electrophysiological attributes of human personality and their relationship were presented. The contribution of this research and the whole book is described here. Also, the focus has been given to the novelty of research findings. In addition, like many other studies, this study has given some answers but at the same time has revealed many more questions. Therefore, various guidelines for future research, and some innovative measurement/methodology proposals have been presented in this last section.

Empirical Research on the Relationship Between Personality and Evoked Brain Potentials

In this section, research aim, problems and hypothesis with the methods and determined research results will be presented. This correlational design research that has been run on a sample of N=54 students in Croatia will be described. The main findings regarding the relationship between personality traits extraversion and evoked brain potentials will be presented. Personality traits that were explored are: extraversion, neuroticism, psychoticism, social desirability, addiction, criminality, empathy, impulsivity, adventurousness, strength of excitation, strength of inhibition, mobility, and depression. Latencies and amplitudes in two trials were investigated for the following evoked brain potentials: N1, P2, N2, P3, and Slow wave activity. Visual oddball paradigm was used for evoking brain activity measured on two occipital and two parietal electrodes. Results on controlled variables, such as: age, sight characteristics, coffee drinking, smoking, taking medications, alcohol and drug consumption, and body exercise, are introduced as well. The correlation analyses revealed a significant relationship between personality traits and evoked brain potentials, especially trait adventurousness and social desirability, due to a too simple and monotonous visual task that was use. The determined findings from the PCA factor analysis with Varimax rotation determined 15 factors that explained 79,611% of the total variance. Series of Hierarchical regression analyses for each personality trait individually revealed, as it was expected, certain visual evoked potentials as significant predictors.

Biologically Based Personality Theories

In this section, the theoretical background of applied personality theory in presented empirical research will be introduced. Biological bases of personality are thoroughly explored within well-known Eysenck's dimensional personality theory (1967). The main postulations of this theory will be presented with the special accent on biological bases of personality, i.e. extraversion and neuroticism. This will bring light on understanding the arousal theory and Brebner-Cooper's model of extraversion. In addition, Strelau's temperament theory (1983) will be presented, regarding its theoretical postulations, main temperament dimensions and its explanation within the frame of understanding the Central Nervous System functioning.