The scaffolding of personality a trait structure for normal and abnormal temperaments

A productive science of personality has evolved in recent decades around two main postulates.

1. A small number of dimensions (factors) provide a basic framework for describing the rich variety of human personality. These factors are high-level traits, derived from models based on investigations characterized by careful consistent measures of individual variations in behaviour, feeling, and thinking. (1.,2,3and4)

2. These general factors of temperament reflect the operation of particular brain systems that are probably multifaceted and multipurpose. (56, and 7)

This global outline of the structure of personality depends on the assumption that genetic and developmental dispositions combine with critical nurturing and social conditioning to form the tapestry of human uniqueness within temperamental clusters. (Throughout this chapter, the terms 'temperament' and 'personality' are used interchangeably because of the continuing debate on how to distinguish between them.) In other words, personality types are expressed through relatively clear-cut and stable traits that are accessible to objective measurement at behavioural, emotional, and cognitive levels. These depend, in turn, upon the specific and early organization of particular neurocognitive and neuroendocrine systems.

The first of the postulates mentioned above has received a good deal of support from most of the psychometric research assessing durable trends for individual personality profiles within and across particular cultures. (34) Currently, there is an increasing consensus that five 'superfactors' (broad traits) may capture the essential features of all traits used to describe normal personality. These superfactors are neuroticism, extraversion, agreeableness/friendliness, conscientiousness, and intellectual openness.

Despite some dissent regarding the exact nature and definition of these superfactors, (89) a five-dimensional structure is advocated by many researchers. (3,4,10) Based on the pioneering programme of research developed by Hans Eysenck at the Institute of Psychiatry, London, neuroticism and extraversion always appear in the dimensional 'menu' which some consider to be the basis of the modern science of personality. However, the remaining three superfactors—conscientiousness (reliability), friendliness (against aggressiveness/hostility), and intellectual curiosity (openness/creativity)—are obvious departures from the three-dimensional structure proposed by Eysenck that included only one more, very controversial, superfactor (psychoticism) to encompass the whole of 'personality space'. It seems improbable that these controversies can be resolved by using psychometric techniques alone.

Determination of the biological substrates for these personality dimensions was neglected by those researchers who preferred a purely psychometric/behavioural approach, although some early theories tried to root behavioural trait variations within biological concepts. (1) These attempts can be traced back as far as Pavlov, but for a long time they were either speculative or very rudimentary. Changes began when several models were produced which focused on certain brain systems and subsystems as possible sites for the factors and traits underlying normal and abnormal temperaments. k^ll,1.2) Currently, this particular area is growing steadily, and is the most exciting and fruitful field of personality research.

Progress made in various fields of basic neuroscience has made it possible to relate a variety of biological markers to the results of paper-and-pencil tests or cognitive-behavioural tests in normal temperaments. Biological screening has increasingly been applied to patients with personality disorders, using the clinical clusters defined in DSM-IV or ICD-10A1J.> As well as these attempts to build consistent psychobiological profiles of normal and abnormal temperaments, an increasing convergence of other evidence has suggested that categorical and dimensional models for diagnosing personality disorders should be integrated. (1. J. and 15

To give a broad overview of an area that may have enormous implications for understanding the aetiopathogenesis of personality disorders, we shall first discuss recent studies that have tried to find genetic evidence for personality raits that are both behaviourally consistent and biologically well established. Previous work using classical (familial or twin) methods found substantial heritability estimates for several personality traits. (1. H) The new data may support the view that some traits contribute to the basic structuring of personality via particular neuroendocrine systems. We shall also explore the possible origins of other basic traits within biodevelopmental processes mediating enduring neural and cognitive organization.

Because of the limitations of space, our approach is deliberately selective, citing supportive evidence rather than performing a systematic assessment of the field. For reasons of convenience and possible clinical relevance, we have selected some of the traits that demonstrate solid biological foundations, although they are not necessarily prominent in the progressively powerful and elegant dimensional solutions for normal and abnormal temperaments. In other words, the following discussion is centred on several primary factors instead of the constellation of superfactors.

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