Neuroticism may not reflect emotional variability Elise K. Kalokerinosa,1,2, Sean C. Murphya,1, Peter Kovala,b, Natasha H. Bailenc, Geert Crombezd, Tom Hollensteine, John Gleesonf, Renee J. Thompsonc, Dimitri M. L. Van Ryckeghemd,g, Peter Kuppensb, and Brock Bastiana aMelbourne School of Psychological Sciences, The University of Melbourne, Parkville, VIC 3010, Australia; bFaculty of Psychology and Educational Sciences, KU Leuven, 3000 Leuven, Belgium; cDepartment of Psychological and Brain Sciences, Washington University in St. Louis, St. Louis, MO 63130-4899; dFaculty of Psychology and Educational Sciences, Ghent University, 9000 Ghent, Belgium; eDepartment of Psychology, Queen’s University, Kingston, ON K7L 3N6, Canada; fSchool of Behavioural and Health Sciences, Australian Catholic University, Fitzroy, VIC 3065, Australia; and gFaculty of Psychology and Neuroscience, Maastricht University, 6229 Maastricht, The Netherlands Edited by Susan T. Fiske, Princeton University, Princeton, NJ, and approved March 12, 2020 (received for review November 12, 2019) Neuroticism is one of the major traits describing human person- as a facet of hierarchical models of neuroticism (e.g., ref. 13). In ality, and a predictor of mental and physical disorders with addition, the major assessment scales have items tapping emo- profound public health significance. Individual differences in tional variability (13–17), meaning that almost all neuroticism emotional variability are thought to reflect the core of neuroti- research incorporates variability. cism. However, the empirical relation between emotional variabil- Emotional variability is commonly operationalized as the ity and neuroticism may be partially the result of a measurement within-person SD of repeated emotion assessments. A meta- artifact reflecting neuroticism’s relation with higher mean levels— analysis of 61 effects found a small-to-medium positive associa- rather than greater variability—of negative emotion. When emo- tion between neuroticism and the negative emotion within- tional intensity is measured using bounded scales, there is a de- person SD (18), providing evidence for this link. However, we pendency between variability and mean levels: at low (or high) argue that findings linking neuroticism to emotional variability intensity, it is impossible to demonstrate high variability. As neu- may be partly the result of a methodological artifact. Variability roticism is positively associated with mean levels of negative emo- in a construct can be dependent on mean levels of the same tion, this may account for the relation between neuroticism and construct, especially when measurements are bounded within N = emotional variability. In a metaanalysis of 11 studies ( 1,205 scales (19). For example, consider a study in which emotions are participants; 83,411 observations), we tested whether the associ- repeatedly assessed on a scale from 0 (no emotion) to 100 ation between neuroticism and negative emotional variability was ’ (strong emotion). Here, a person s mean will always fall between PSYCHOLOGICAL AND COGNITIVE SCIENCES clouded by a dependency between variability and the mean. We 0 and 100. If their mean is low (e.g., 10) or high (e.g., 90), their found a medium-sized positive association between neuroticism variability is limited by the scale endpoints. That is, a person with and negative emotional variability, but, when using a relative var- a mean of 10 (or a mean of 90) cannot demonstrate as much iability index to correct for mean negative emotion, this associa- variability as somebody with a mean of 50, since the scores of the tion disappeared. This indicated that neuroticism was associated with experiencing more intense, but not more variable, negative latter individual are less constrained by the scale boundaries. In emotions. Our findings call into question theory, measurement line with this, low mean levels of emotion are associated with scales, and data suggesting that emotional variability is central lower emotional variability (20, 21). to neuroticism. In doing so, they provide a revisionary perspective for understanding how this individual difference may predispose Significance to mental and physical disorders. Neuroticism is the personality trait most closely linked with neuroticism | negative emotion | emotional variability | personality | mental health challenges. Thus, it is important to understand experience sampling how neuroticism manifests in everyday experience. Neuroti- cism has been characterized by greater variability between ariation in human personality is commonly described in high and low levels of negative emotion. However, the way Vterms of a handful of organizing dimensions (1). A di- negative emotion is often measured means that there is a mension that features in most, if not all, taxonomies of person- dependency between variability and the mean, which is ality is neuroticism (1). Neuroticism is typified by negative problematic because neuroticism is also associated with high emotionality (2), and, as such, is central for understanding dif- mean levels of negative emotion. In a metaanalysis of 11 ferential risk in mental and physical health (3) and has profound studies that investigated emotion in everyday life, we found public health significance (4). Neuroticism is such a powerful that, after accounting for the mean, neuroticism was not as- predictor of future emotional disorder that some scholars have sociated with emotional variability. This calls into question the proposed that clinical efforts shift toward directly targeting definition of neuroticism and therefore how its association neuroticism (3). However, this requires a full understanding of with mental illness is best understood. how neuroticism manifests in everyday emotional experience, Author contributions: E.K.K., S.C.M., P. Koval, P. Kuppens, and B.B. designed research; which we argue may be lacking. E.K.K., S.C.M., P. Koval, N.H.B., G.C., T.H., J.G., R.J.T., D.M.L.V.R., P. Kuppens, and B.B. The negative emotionality central to neuroticism is thought to performed research; E.K.K. and S.C.M. analyzed data; and E.K.K. and S.C.M. wrote manifest not only in higher mean levels of negative emotion, but the paper. also in greater emotional variability (5). Emotional variability is a The authors declare no competing interest. core part of Eysenck’s foundational conceptualization of neu- This article is a PNAS Direct Submission. roticism (6), which described neuroticism as hyperreactivity Published under the PNAS license. manifesting in emotional volatility. This centrality of variability Data deposition: Our data are available on the Open Science Framework at https://osf.io/ to neuroticism has inspired more recent research (e.g., ref. 7), gvfdx/. and there is even a body of research testing whether emotional 1E.K.K. and S.C.M. contributed equally to this work. variability and neuroticism are separable concepts (5, 8–10). This 2To whom correspondence may be addressed. Email: [email protected]. link is also strongly reflected in the measurement of neuroticism: This article contains supporting information online at https://www.pnas.org/lookup/suppl/ most scholars use “emotional stability” as the inverse of neu- doi:10.1073/pnas.1919934117/-/DCSupplemental. roticism (e.g., refs. 11 and 12), and scales often include variability www.pnas.org/cgi/doi/10.1073/pnas.1919934117 PNAS Latest Articles | 1of7 Downloaded by guest on October 1, 2021 This mean–variability dependency is likely to interfere with the studies of emotional variability (18). These methods are ideal for association between neuroticism and negative emotional vari- capturing variability because they allow for the collection of ability for three reasons. First, measurements of emotional ex- many data points (increasing the reliability of variability indices) perience are bounded by scale endpoints. Second, emotional and index emotions across varied contexts. Using these methods, variability is usually calculated using reports of emotion in ev- participants are not asked to self-report emotional variability; eryday life (18), where most people encounter few intense neg- instead, variability is computed by calculating variance across ative events (22), meaning negative emotional experience is momentary reports. often near the scale floor. This results in low mean scores, pre- We focused on negative emotion, as neuroticism is theoreti- cluding participants from demonstrating high variability. Third, cally centered on negative, rather than positive, emotionality low neuroticism is associated with low mean levels of negative (15). Our key measure of variability was the within-person SD of emotion (e.g., ref. 23). As such, less neurotic individuals may be negative emotion (18). We replicated our analyses using the constrained to have lower emotional variability simply because mean squared successive difference (MSSD), which captures the they experience low average levels of negative emotion. Thus, temporal aspect of instability between measurements (25) and findings showing emotional variability is linked with neuroticism suffers from the same issues as the within-person SD (24). may be a byproduct of the link with mean levels of negative Our analyses consisted of five steps. In the first two steps, we emotion, with mean levels providing a more parsimonious ac- investigated whether the mean–variability dependency was likely count of the relationship. to be problematic. We tested the associations between neuroti- To