Developing "Personality" Taxonomies: Metatheoretical and Methodological Rationales Underlying Selection Approaches, Methods of Data Generation and Reduction Principles

Rating scales institutionalise a network of logical errors and conceptual problems in research practices: A rigorous analysis showing ways to tackle psychology's crises

This article explores in-depth the metatheoretical and methodological foundations on which rating scales-by their very conception, design and application-are built and traces their historical origins. It brings together independent lines of critique from different scholars and disciplines to map out the problem landscape, which centres on the failed distinction between psychology's study phenomena (e.g., experiences, everyday constructs) and the means of their exploration (e.g., terms, data, scientific constructs)-psychologists' cardinal error. Rigorous analyses reveal a dense network of 12 complexes of problematic concepts, misconceived assumptions and fallacies that support each other, making it difficult to be identified and recognised by those (unwittingly) relying on them (e.g., various forms of reductionism, logical errors of operationalism, constructification, naïve use of language, quantificationism, statisticism, result-based data generation, misconceived nomotheticism). Through the popularity of rating scales for efficient quantitative data generation, uncritically interpreted as psychological measurement, these problems have become institutionalised in a wide range of research practices and perpetuate psychology's crises (e.g., replication, confidence, validation, generalizability). The article provides an in-depth understanding that is needed to get to the root of these problems, which preclude not just measurement but also the scientific exploration of psychology's study phenomena and thus its development as a science. From each of the 12 problem complexes; specific theoretical concepts, methodologies and methods are derived as well as key directions of development. The analyses-based on three central axioms for transdisciplinary research on individuals, (1) complexity, (2) complementarity and (3) anthropogenicity-highlight that psychologists must (further) develop an explicit metatheory and unambiguous terminology as well as concepts and theories that conceive individuals as living beings, open self-organising systems with complementary phenomena and dynamic interrelations across their multi-layered systemic contexts-thus, theories not simply of elemental properties and structures but of processes, relations, dynamicity, subjectivity, emergence, catalysis and transformation. Philosophical and theoretical foundations of approaches suited for exploring these phenomena must be developed together with methods of data generation and methods of data analysis that are appropriately adapted to the peculiarities of psychologists' study phenomena (e.g., intra-individual variation, momentariness, contextuality). Psychology can profit greatly from its unique position at the intersection of many other disciplines and can learn from their advancements to develop research practices that are suited to tackle its crises holistically.

Comparison of individualized behavioral predictions across anatomical, diffusion and functional connectivity MRI

A fundamental goal across the neurosciences is the characterization of relationships linking brain anatomy, functioning, and behavior. Although various MRI modalities have been developed to probe these relationships, direct comparisons of their ability to predict behavior have been lacking. Here, we compared the ability of anatomical T1, diffusion and functional MRI (fMRI) to predict behavior at an individual level. Cortical thickness, area and volume were extracted from anatomical T1 images. Diffusion Tensor Imaging (DTI) and approximate Neurite Orientation Dispersion and Density Imaging (NODDI) models were fitted to the diffusion images. The resulting metrics were projected to the Tract-Based Spatial Statistics (TBSS) skeleton. We also ran probabilistic tractography for the diffusion images, from which we extracted the stream count, average stream length, and the average of each DTI and NODDI metric across tracts connecting each pair of brain regions. Functional connectivity (FC) was extracted from both task and resting-state fMRI. Individualized prediction of a wide range of behavioral measures were performed using kernel ridge regression, linear ridge regression and elastic net regression. Consistency of the results were investigated with the Human Connectome Project (HCP) and Adolescent Brain Cognitive Development (ABCD) datasets. In both datasets, FC-based models gave the best prediction performance, regardless of regression model or behavioral measure. This was especially true for the cognitive component. Furthermore, all modalities were able to predict cognition better than other behavioral components. Combining all modalities improved prediction of cognition, but not other behavioral components. Finally, across all behaviors, combining resting and task FC yielded prediction performance similar to combining all modalities. Overall, our study suggests that in the case of healthy children and young adults, behaviorally-relevant information in T1 and diffusion features might reflect a subset of the variance captured by FC.

Psychology's Status as a Science: Peculiarities and Intrinsic Challenges. Moving Beyond its Current Deadlock Towards Conceptual Integration

Psychology holds an exceptional position among the sciences. Yet even after 140 years as an independent discipline, psychology is still struggling with its most basic foundations. Its key phenomena, mind and behaviour, are poorly defined (and their definition instead often delegated to neuroscience or philosophy) while specific terms and constructs proliferate. A unified theoretical framework has not been developed and its categorisation as a 'soft science' ascribes to psychology a lower level of scientificity. The article traces these problems to the peculiarities of psychology's study phenomena, their interrelations with and centrality to everyday knowledge and language (which may explain the proliferation and unclarity of terms and concepts), as well as to their complex relations with other study phenomena. It shows that adequate explorations of such diverse kinds of phenomena and their interrelations with the most elusive of all-immediate experience-inherently require a plurality of epistemologies, paradigms, theories, methodologies and methods that complement those developed for the natural sciences. Their systematic integration within just one discipline, made necessary by these phenomena's joint emergence in the single individual as the basic unit of analysis, makes psychology in fact the hardest science of all. But Galtonian nomothetic methodology has turned much of today's psychology into a science of populations rather than individuals, showing that blind adherence to natural-science principles has not advanced but impeded the development of psychology as a science. Finally, the article introduces paradigmatic frameworks that can provide solid foundations for conceptual integration and new developments.

Taxonomic models of individual differences: a guide to transdisciplinary approaches

Models and constructs of individual differences are numerous and diverse. But detecting commonalities, differences and interrelations is hindered by the common abstract terms (e.g. 'personality', 'temperament', 'traits') that do not reveal the particular phenomena denoted. This article applies a transdisciplinary paradigm for research on individuals that builds on complexity theory and epistemological complementarity. Its philosophical, metatheoretical and methodological frameworks provide concepts to differentiate various kinds of phenomena (e.g. physiology, behaviour, psyche, language). They are used to scrutinize the field's basic concepts and to elaborate methodological foundations for taxonomizing individual variations in humans and other species. This guide to developing comprehensive and representative models explores the decisions taxonomists must make about which individual variations to include, which to retain and how to model them. Selection and reduction approaches from various disciplines are classified by their underlying rationales, pinpointing possibilities and limitations. Analyses highlight that individuals' complexity cannot be captured by one universal model. Instead, multiple models phenotypically taxonomizing different kinds of variability in different kinds of phenomena are needed to explore their causal and functional interrelations and ontogenetic development that are then modelled in integrative and explanatory taxonomies. This research agenda requires the expertise of many disciplines and is inherently transdisciplinary.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Diversity in action: exchange of perspectives and reflections on taxonomies of individual differences

Throughout the last 2500 years, the classification of individual differences in healthy people and their extreme expressions in mental disorders has remained one of the most difficult challenges in science that affects our ability to explore individuals' functioning, underlying psychobiological processes and pathways of development. To facilitate analyses of the principles required for studying individual differences, this theme issue brought together prominent scholars from diverse backgrounds of which many bring unique combinations of cross-disciplinary experiences and perspectives that help establish connections and promote exchange across disciplines. This final paper presents brief commentaries of some of our authors and further scholars exchanging perspectives and reflecting on the contributions of this theme issue.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Quantitative Data From Rating Scales: An Epistemological and Methodological Enquiry

Rating scales are popular methods for generating quantitative data directly by persons rather than automated technologies. But scholars increasingly challenge their foundations. This article contributes epistemological and methodological analyses of the processes involved in person-generated quantification. They are crucial for measurement because data analyses can reveal information about study phenomena only if relevant properties were encoded systematically in the data. The Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals (TPS-Paradigm) is applied to explore psychological and social-science concepts of measurement and quantification, including representational measurement theory, psychometric theories and their precursors in psychophysics. These are compared to theories from metrology specifying object-dependence of measurement processes and subject-independence of outcomes as key criteria, which allow tracing data to the instances measured and the ways they were quantified. Separate histories notwithstanding, the article's basic premise is that general principles of scientific measurement and quantification should apply to all sciences. It elaborates principles by which these metrological criteria can be implemented also in psychology and social sciences, while considering their research objects' peculiarities. Application of these principles is illustrated by quantifications of individual-specific behaviors ('personality'). The demands rating methods impose on data-generating persons are deconstructed and compared with the demands involved in other quantitative methods (e.g., ethological observations). These analyses highlight problematic requirements for raters. Rating methods sufficiently specify neither the empirical study phenomena nor the symbolic systems used as data nor rules of assignment between them. Instead, pronounced individual differences in raters' interpretation and use of items and scales indicate considerable subjectivity in data generation. Together with recoding scale categories into numbers, this introduces a twofold break in the traceability of rating data, compromising interpretability of findings. These insights question common reliability and validity concepts for ratings and provide novel explanations for replicability problems. Specifically, rating methods standardize only data formats but not the actual data generation. Measurement requires data generation processes to be adapted to the study phenomena's properties and the measurement-executing persons' abilities and interpretations, rather than to numerical outcome formats facilitating statistical analyses. Researchers must finally investigate how people actually generate ratings to specify the representational systems underlying rating data.

Resting-state functional brain connectivity best predicts the personality dimension of openness to experience

Personality neuroscience aims to find associations between brain measures and personality traits. Findings to date have been severely limited by a number of factors, including small sample size and omission of out-of-sample prediction. We capitalized on the recent availability of a large database, together with the emergence of specific criteria for best practices in neuroimaging studies of individual differences. We analyzed resting-state functional magnetic resonance imaging data from 884 young healthy adults in the Human Connectome Project (HCP) database. We attempted to predict personality traits from the "Big Five", as assessed with the NEO-FFI test, using individual functional connectivity matrices. After regressing out potential confounds (such as age, sex, handedness and fluid intelligence), we used a cross-validated framework, together with test-retest replication (across two sessions of resting-state fMRI for each subject), to quantify how well the neuroimaging data could predict each of the five personality factors. We tested three different (published) denoising strategies for the fMRI data, two inter-subject alignment and brain parcellation schemes, and three different linear models for prediction. As measurement noise is known to moderate statistical relationships, we performed final prediction analyses using average connectivity across both imaging sessions (1 h of data), with the analysis pipeline that yielded the highest predictability overall. Across all results (test/retest; 3 denoising strategies; 2 alignment schemes; 3 models), Openness to experience emerged as the only reliably predicted personality factor. Using the full hour of resting-state data and the best pipeline, we could predict Openness to experience (NEOFAC_O: r=0.24, R2=0.024) almost as well as we could predict the score on a 24-item intelligence test (PMAT24_A_CR: r=0.26, R2=0.044). Other factors (Extraversion, Neuroticism, Agreeableness and Conscientiousness) yielded weaker predictions across results that were not statistically significant under permutation testing. We also derived two superordinate personality factors ("α" and "β") from a principal components analysis of the NEO-FFI factor scores, thereby reducing noise and enhancing the precision of these measures of personality. We could account for 5% of the variance in the β superordinate factor (r=0.27, R2=0.050), which loads highly on Openness to experience. We conclude with a discussion of the potential for predicting personality from neuroimaging data and make specific recommendations for the field.

Taxonomies of psychological individual differences: biological perspectives on millennia-long challenges

This Editorial highlights a unique focus of this theme issue on the biological perspectives in deriving psychological taxonomies coming from neurochemistry, neuroanatomy, neurophysiology, genetics, psychiatry, developmental and comparative psychology-as contrasted to more common discussions of socio-cultural concepts (personality) and methods (lexical approach). It points out the importance of the distinction between temperament and personality for studies in human and animal differential psychophysiology, psychiatry and psycho-pharmacology, sport and animal practices during the past century. It also highlights the inability of common statistical methods to handle nonlinear, feedback, contingent, dynamical and multi-level relationships between psychophysiological systems of consistent psychological traits discussed in this theme issue.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Functionality versus dimensionality in psychological taxonomies, and a puzzle of emotional valence

This paper applies evolutionary and functional constructivism approaches to the discussion of psychological taxonomies, as implemented in the neurochemical model Functional Ensemble of Temperament (FET). FET asserts that neurochemical systems developed in evolution to regulate functional-dynamical aspects of construction of actions: orientation, selection (integration), energetic maintenance, and management of automatic behavioural elements. As an example, the paper reviews the neurochemical mechanisms of interlocking between emotional dispositions and performance capacities. Research shows that there are no specific neurophysiological systems of positive or negative affect, and that emotional valence is rather an integrative product of many brain systems during estimations of needs and the capacities required to satisfy these needs. The interlocking between emotional valence and functional aspects of performance appears to be only partial since all monoamine and opioid receptor systems play important roles in non-emotional aspects of behaviour, in addition to emotionality. This suggests that the Positive/Negative Affect framework for DSM/ICD classifications of mental disorders oversimplifies the structure of non-emotionality symptoms of these disorders. Contingent dynamical relationships between neurochemical systems cannot be represented by linear statistical models searching for independent dimensions (such as factor analysis); nevertheless, these relationships should be reflected in psychological and psychiatric taxonomies.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

The Future of Personality Theory: a Processual Approach

The perpetual discussion of approaches and principles in the study of personality has been one of the notable trends of development of psychological science over many decades. The structural approach, based on the delineation of a person's traits and characteristics, made an important contribution to various branches of psychology, but now the scientific community has recognized the limitations of a structural understanding of personality. Its inadequacy becomes particularly obvious in today's conditions, when fundamental changes pose a challenge to man's ability to respond flexibly to changing conditions of everyday existence, as well as to larger-scale changes. At the beginning of the twenty-first century, it is obvious that there is a need for new ways to understand and describe the personality: Scholars are calling for study of the dynamic personality, of the personality as an open system. At the foundational level, modern personality psychology should incorporate classical ideas about its structure; secondly, it should consider personality in the context of the individual's lifetime; and - at the highest level - it should describe personality as the subject of Being. We submit our own description of personality psychology's problem field.

Individual personality is best understood as process, not structure: A Confucian-inspired perspective

A structural approach to understanding personality, which is rooted in a being or substance ontology, is most useful for making between individual and group comparisons. In contrast, a process-centric approach, which is anchored in a Becoming or event-based ontology, is most helpful for understanding individual personality process and variation. A process-centric model, using classical Confucianism as a starting point, has a number of advantages in that it (1) integrates persons and situations, (2) is inherently relational, which implies an aesthetic dimension to personality development and functioning, (3) focuses on the uniqueness of individual personalities, (4) views qualitative and quantitative inquiry as complementary and of equal scientific value, and (5) encourages intra- and inter-disciplinary collaborations.

Interpreting "Personality" Taxonomies: Why Previous Models Cannot Capture Individual-Specific Experiencing, Behaviour, Functioning and Development. Major Taxonomic Tasks Still Lay Ahead

As science seeks to make generalisations, a science of individual peculiarities encounters intricate challenges. This article explores these challenges by applying the Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals (TPS-Paradigm) and by exploring taxonomic "personality" research as an example. Analyses of researchers' interpretations of the taxonomic "personality" models, constructs and data that have been generated in the field reveal widespread erroneous assumptions about the abilities of previous methodologies to appropriately represent individual-specificity in the targeted phenomena. These assumptions, rooted in everyday thinking, fail to consider that individual-specificity and others' minds cannot be directly perceived, that abstract descriptions cannot serve as causal explanations, that between-individual structures cannot be isomorphic to within-individual structures, and that knowledge of compositional structures cannot explain the process structures of their functioning and development. These erroneous assumptions and serious methodological deficiencies in widely used standardised questionnaires have effectively prevented psychologists from establishing taxonomies that can comprehensively model individual-specificity in most of the kinds of phenomena explored as "personality", especially in experiencing and behaviour and in individuals' functioning and development. Contrary to previous assumptions, it is not universal models but rather different kinds of taxonomic models that are required for each of the different kinds of phenomena, variations and structures that are commonly conceived of as "personality". Consequently, to comprehensively explore individual-specificity, researchers have to apply a portfolio of complementary methodologies and develop different kinds of taxonomies, most of which have yet to be developed. Closing, the article derives some meta-desiderata for future research on individuals' "personality".

Developing "Personality" Taxonomies: Metatheoretical and Methodological Rationales Underlying Selection Approaches, Methods of Data Generation and Reduction Principles

Taxonomic "personality" models are widely used in research and applied fields. This article applies the Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals (TPS-Paradigm) to scrutinise the three methodological steps that are required for developing comprehensive "personality" taxonomies: 1) the approaches used to select the phenomena and events to be studied, 2) the methods used to generate data about the selected phenomena and events and 3) the reduction principles used to extract the "most important" individual-specific variations for constructing "personality" taxonomies. Analyses of some currently popular taxonomies reveal frequent mismatches between the researchers' explicit and implicit metatheories about "personality" and the abilities of previous methodologies to capture the particular kinds of phenomena toward which they are targeted. Serious deficiencies that preclude scientific quantifications are identified in standardised questionnaires, psychology's established standard method of investigation. These mismatches and deficiencies derive from the lack of an explicit formulation and critical reflection on the philosophical and metatheoretical assumptions being made by scientists and from the established practice of radically matching the methodological tools to researchers' preconceived ideas and to pre-existing statistical theories rather than to the particular phenomena and individuals under study. These findings raise serious doubts about the ability of previous taxonomies to appropriately and comprehensively reflect the phenomena towards which they are targeted and the structures of individual-specificity occurring in them. The article elaborates and illustrates with empirical examples methodological principles that allow researchers to appropriately meet the metatheoretical requirements and that are suitable for comprehensively exploring individuals' "personality".

Conceiving "personality": Psychologist's challenges and basic fundamentals of the Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals

Scientists exploring individuals, as such scientists are individuals themselves and thus not independent from their objects of research, encounter profound challenges; in particular, high risks for anthropo-, ethno- and ego-centric biases and various fallacies in reasoning. The Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals (TPS-Paradigm) aims to tackle these challenges by exploring and making explicit the philosophical presuppositions that are being made and the metatheories and methodologies that are used in the field. This article introduces basic fundamentals of the TPS-Paradigm including the epistemological principle of complementarity and metatheoretical concepts for exploring individuals as living organisms. Centrally, the TPS-Paradigm considers three metatheoretical properties (spatial location in relation to individuals' bodies, temporal extension, and physicality versus "non-physicality") that can be conceived in different forms for various kinds of phenomena explored in individuals (morphology, physiology, behaviour, the psyche, semiotic representations, artificially modified outer appearances and contexts). These properties, as they determine the phenomena's accessibility in everyday life and research, are used to elaborate philosophy-of-science foundations and to derive general methodological implications for the elementary problem of phenomenon-methodology matching and for scientific quantification of the various kinds of phenomena studied. On the basis of these foundations, the article explores the metatheories and methodologies that are used or needed to empirically study each given kind of phenomenon in individuals in general. Building on these general implications, the article derives special implications for exploring individuals' "personality", which the TPS-Paradigm conceives of as individual-specificity in all of the various kinds of phenomena studied in individuals.

Being or Becoming: Toward an Open-System, Process-Centric Model of Personality

Mainstream personality psychology in the West neglects the investigation of intra-individual process and variation, because it favors a Being over a Becoming ontology. A Being ontology privileges a structural (e.g., traits or selves) conception of personality. Structure-centric models in turn suggest nomothetic research strategies and the investigation of individual and group differences. This article argues for an open-system, process-centric understanding of personality anchored in an ontology of Becoming. A classical Confucian model of personality is offered as an example of a process-centric approach for investigating and appreciating within-person personality process and variation. Both quantitative and qualitative idiographic strategies can be used as methods of scientific inquiry, particularly the exploration of the Confucian exemplar of psychological health and well-being.

The Big Five Factor Marker Adjectives Are Not Especially Popular Words. Are They Superior Descriptors?

Vocabularies of natural languages evolve over time. Useful words become more popular and useless concepts disappear. In this study, the frequency of the use of 295 English, 100 German, and 114 French personality adjectives in book texts and Twitter messages as qualifiers of the words person, woman, homme, femme, and Person was studied. Word frequency data were compared to factor loadings from previous factor analytic studies on personality terms. The correlation between the popularity of an adjective and its highest primary loading in five- and six-factor models was low (-0.12 to 0.17). The Big five (six) marker adjectives were not more popular than "blended" adjectives that had moderate loadings on several factors. This finding implies that laymen consider "blended" adjectives as equally useful descriptors compared to adjectives that represent core features of the five (six) factors. These results are compatible with three hypotheses: 1) laymen are not good at describing personality, 2) the five (six) factors are artifacts of research methods, 3) the interaction of the five (six) factors is not well understood.

Is Personality a System? Stability, Process and Plasticity

The nomothetic thrust of personality research has been the subject of some significant recent criticism. One major problem is the failure in much personality research to sufficiently scrutinize its methods and its background beliefs. This produces conceptual schematizations of personality that do not sufficiently take into account the disunity and plasticity that affects what is construed as personality; it also underplays the necessity of more fully theorizing the network of infrapsychic and transpersonal systems, processes, structures, templates, interfaces, flows of stimuli, qualities of embodiment and contingencies that dynamically manifest as personality. It is through unfolding the complexity inherent in this network that personality theorization can move forward in new ways. This paper provides a provisional, beginning taxonomy of this network in order to start a research dialogue about personality that doesn't begin with the operative background beliefs of nomothetic methodology, that doesn't tacitly or overtly construe the individual to be a self-regulating, homeostatic system, and that resists presupposing personality as a cohesive, stable quality of personhood.