Three Methodological Core Issues of Comparative Personality Research

Comparative personality research in human and nonhuman species advances many areas of empirical and theoretical research. The methodological foundations underlying these attempts to explain personality, however, remain an unpopular and often ignored topic. The target paper and this rejoinder explore three methodological core issues in the philosophy of science for comparative personality research: Conceptualising personality variation, identifying domains of variation and measuring variation. Clear distinctions among these issues may help to avoid misunderstandings among different disciplines concerned with personality. Copyright # 2008 John Wiley & Sons, Ltd. I am delighted that colleagues from different disciplines commented on my target paper and I sincerely thank all commentators for their insightful contributions. Personality is studied from very different viewpoints; my attempt to consolidate some basic methodological issues across disciplines was therefore predestined to meet with some scepticism. The pattern of agreement and objection raised in the commentaries thus closely reflects the field’s current fragmentation across different disciplines and demonstrates much better than any single author could do how largely unaware most disciplines are of developments in neighbouring fields. None of the methodological issues I proposed was criticised by all disciplines and the objections raised by some are countered by commentaries of others. What a potential for synergy! Concepts and findings of different disciplines are waiting to be systematically integrated to form a multidisciplinary and more complex knowledge base that has the potential to advance the field significantly. Copyright # 2008 John Wiley & Sons, Ltd. *Correspondence to: Jana Uher, Psychological Institute, Humboldt University Berlin, Rudower Chaussee 18, 12489 Berlin, Germany. E-mail: [email protected] Removing the invisible barriers between disciplines is a major challenge. Not only is there a Babylonian gap that could be crossed by simple dictionary-like translation; but there are also difficulties understanding similarities and differences in the concepts underlying the disciplines’ standard terms. Since each discipline has its own good reasons for its specific perspective on personality, attempts for conceptual integrations across disciplines are only possible with risk taking, openness to other perspectives and compromise. Unlike empirical findings, concepts and methodologies are designed to be modified and changed as empirical facts accumulate and alternative perspectives are proposed. It was my aim to encourage this kind of discussion by addressing a multidisciplinary audience. In my rejoinder, I discuss the issues raised by the different commentators from animal personality psychology (Weiss & Adams), behavioural ecology (van Oers), behaviour genetics (Johnson), cross-cultural psychology (Realo & Allik), developmental psychology (van Aken), human personality psychology (Nave, Sherman & Funder; Nettle), neurobiology and psychobiology (Carere & Maestripieri) within a common methodological framework, and highlight perspectives for future research. INTEGRATING THREE EPISTEMIC ISSUES WITHIN A COMMON METHODOLOGICAL FRAMEWORK Personality in the broadest sense is the internal organisation of behaviour that is stable over considerable time periods in the individual yet varies among the individuals of a population on latent dimensions. To identify such dimensions, I offered several methodological suggestions based on pertinent approaches in cross-cultural research on the one hand and on philosophical traditions of science and well-established findings in trait psychology on the other hand. The overall methodological framework I proposed integrates three different core issues that have to be distinguished from one another and that require different types of approaches. The first is a methodology to conceptualise the basic phenomenon of personality variation in different populations within and across species as structures recurring in the same qualitative form in different individuals but at different quantitative levels that constitute dimensions across the composite of a population. The second is a methodology to identify in which domains (e.g. in shyness–boldness, sociability or conscientiousness) such dimensions are exhibited by a particular population. The third covers methodological approaches to measure such dimensions in these domains in the given population empirically. It is obvious that all three issues are necessarily interdependent but refer to different epistemological stages that merge together in the concept of hierarchical trait taxonomies (Figure 1). Dimensional conceptions of personality vary greatly in complexity across different disciplines. In biological disciplines, they range from variation in single behavioural measures (called proxies, van Oers) to more complex dimensions (called continua or axes), which also underlie the recent concept of behavioural syndromes as clusters (or suites) of correlated behaviours (also called traits or characters; Sih, Bell, Johnson, & Ziemba, 2004). This latter concept explicitly incorporates the pervasive empirical finding that single behavioural dimensions often covary empirically, thus forming a more complex higher order dimension. Psychological disciplines study dimensionality of high complexity and therefore obtain many different trait indicators. In trait taxonomies, narrow trait 476 Discussion Copyright # 2008 John Wiley & Sons, Ltd. Eur. J. Pers. 22: 475–496 (2008)