An epistemic unification of the nomothetic and idiographic perspectives in psychopathology using scaling lenses

Based on the original definitions of Windelband in 1894, we classify nomothetic and idiographic approaches in scientific research as methodological perspectives of the same (latent) construct observed in different scales of observation (Windelband, 1894). Often, the nomothetic (in psychology, defined as research on the group-level) and idiographic (the individual-level) approaches are seen as contrasting views. However, in daily life many concepts studied in nomothetic designs are used in practice in the context of the individual. For example, treatment guidelines in mental health clinics are often based on nomothetic research, while the experience of mental health is mostly person specific. Therefore, bridging the gap between the nomothetic and idiographic may lead to a form of mediation or dialogue between these, and lead to more holistic information of the concept of interest studied. Other studies have made attempts to bridge the nomothetic and idiographic gap with the use of statistical methods such as clustering or data-pooling techniques. However, these methods fall short when the aim of a study is a holistic picture (i.e., the inclusion of multiple perspective; the nomothetic, idiographic, and in-between perspective of a person or group). Instead, clustering, data-pooling, or similar methods may ultimately focus on only one, in-between, perspective – or in the case of the cluster, may be reverted to a different form of nomothetic perspective. Rather than purely methodological we will instead take an epistemic route to unify these perspectives. We will begin by applying the conceptual idea of scaling (i.e., how the properties of a system changes over the perspective/size of observation), adopted from the complex systems framework to Windelband’s classification of idiographic and nomothetic. Moreover, we will illustrate this with the application of (cross-) recurrence quantification analyses (Marwan et al., 2025) of the psychological construct anhedonia with systematically changing parameter settings. In this way, we aim to investigate inferences of the nomothetic, idiographic, and between-scales of the construct of interest for an individual at the same time. More variables were measured (as will be seen later), but to keep the illustration as simple as possible, two ecological momentary assessment (EMA) items of anhedonia were chosen due to both their clinical relevance in relation to affective disorders such as depression and due to items related to anhedonia often exhibiting high levels of within-person variance and heterogeneity. To illustrate the aforementioned unification, we opted to use (cross-) recurrence quantification analysis as this form of analysis does not have any assumptions attached to it as it is purely descriptive and allows us to quantify various inferable dynamic properties (indices of system dynamics, such as, determinism [a measure of predictability], entropy [a measure of complexity], and laminarity [a measure of the ‘stickiness’ of recurring states]). These indices, and more, may help us to understand and label the dynamics of an individual’s anhedonia. To implement the idea of scaling to this we systematically change the threshold parameter setting (i.e., the radius of identification) by clustering (via hierarchical clustering) the similarities of the indices between people. In other words, we derive a person-specific (by looking for a radius that results in a recurrence plot to have 5% +/- 1.5% recurrence) and aggregate (of the person-specific radii) radius, calculate indices based on the used radii on finding recurrences in anhedonia, cluster people based on the indices twice (once from the results on the person-specific radius and again based on the results from the aggregate radius) and use the average person-specific radius of the clusters formed to inspect the indices based on these radii. In conclusion, four (cross-) recurrence quantification analyses of the same data per person. We will argue that these lenses illustrate different informative perspectives pertaining to their relative scale of the same construct that cannot be observed by solely focusing on one inferable perspective (i.e., clustered, idiographic, or nomothetic). We aim to illustrate that the unification of seemingly contrasting perspectives of psychological constructs is possible and that attempts should be made to attempt to find value in – and be more open to – the adoption of multi-perspective approaches and the application thereof. 1. Windelband, W. (1894). History and Natural Science. Theory & Psychology, 8(1), 5–22. 2. Marwan, N., Romano, M. C., Thiel, M., & Kurths, J. (2025). Recurrence Plots for the Analysis of Complex Systems. arXiv (Cornell University).