[corrected 8/6/2019 5.29pm – there was a mistake in the model for worry]

After behaviorism banned emotions as scientific constructs and cognitivism viewed humans as computers, the 1980s witnessed the affective revolution. Finally, psychologists were again allowed to study feelings.

The 1980s also were a time where personality psychologists agreed on the Big Five as a unified model of personality traits. Accordingly, personality can be efficiently summarized by individuals’ standing on five dimensions: Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness.

Not surprisingly, the 1980s also produced a model of personalty, emotions (affect), and well-being that has survived until today. The model was first proposed by Costa and McCrae in 1980 (see Schimmack, 2019, for details). This model assumed that extraversion is a disposition to experience more positive affect, neuroticism is a disposition to experience more negative affect, and the balance of positive and negative affect is a major determinant of life-satisfaction. As extraversion and neuroticism are independent dimensions, the model also assumed that positive affect and negative affect are independent, which led to the creation of the widely used Positive Affect and Negative Affect Schedule (Watson et al., 1988) as a measure of well-being.

The model also assumed that general affective dispositions account for most of the stability in well-being over time, while environmental factors produce only momentary and short-lived fluctuations around dispositional levels of well-being (Diener, 1984; Lykken & Tellgen, 1996). This model dominated well-being research in psychology for 20 years (see Diener, Suh, Lucas, & Smith, 1999, for a review).

However, when Positive Psychology emerged at the beginning of the new millenium, psychologists focus shifted from the influence of stable dispositions to factors that could be changed with interventions to boost individuals’ wellbeing (Seligman & Csikszentmihalyi, 2000) and some articles even questioned the influence of dispositions on well-being (Diener, Lucas, & Scollon, 1996). As a result, the past 20 years have seen very little new research on dispositional influences on well-being. The last major article is a meta-analysis that showed positive correlations of extraversion and neuroticism with several well-being indicators (Steel, Schmidt, & Shultz, 2008).

Revisiting the Evidence

There is robust evidence for the influence of neuroticism on wellbeing. Most important, this relationship has been demonstrated in multi-method studies that control for shared method variance when self-ratings of personality are correlated with self-ratings of well-being (McCrae & Costa, 1991; Schimmack, Oishi, Funder, & Furr, 2004). However, the relationship between extraversion and well-being is not as strong or consistent as one would expect based on Costa and McCrae’s (1980) model. For example, McCrae and Costa failed to find evidence for this relationship in a multi-method study, and other studies that controlled for response styles also failed to find the predicted effect (Schimmack, Schupp, & Wagner, 2008).

Taking a closer look at Costa and McCrae’s (1980) article, we see that they did not include life-satisfaction measures in their study. The key empirical finding supporting their model is that extraversion facets like sociabilty measured at time 1 predict positive affect and hedonic balance (positive affect minus negative affect) concurrently and longitudinally and that these correlations remain fairly stable over time. This suggests that personality is stable and contributes to the stable variance in the affect measures. However, the effect size is small (r = .22 to .24). This suggests that extraversion accounts for about 5% of the variance in affect. This finding hardly supports the claim that extraversion accounts for half of the stable variance in well-being.

It is symptomatic of psychology that subsequent articles run with the story while ignoring gaps in the actual empirical evidence. As longitudinal studies in psychology are rare, there have been few attempts to replicate Costa and McCrae’s findings.

Headey and Wearing (1989) replicated and extended Costa and McCrae’s study by including life-satisfaction measures as an indicator of wellbeing. They replicated the key findings and showed that personality also predicts future life-satisfaction. However, the effect size for extraversion was again fairly small; as was the effect of neuroticism, suggesting that most of the stable variance in life-satisfaction is not explained by extraversion and neuroticism.

A key limitation of both studies is that they do not take shared method variance into account. Although method variance may be transient, it is also possible that it is stable over time (Anusic et al., 2009). Thus, even the already modest effect sizes may still be inflated by shared method variance.

New Evidence

Data and Model

Fortunately, better data are now available to revisit the longitudinal relationships between personality and life-satisfaction. I used the data from the German Socio-Economic Panel (SOEP). The SOEP measured the Big Five personality traits on four occasions (waves) spanning a period of 12 years (2005, 2009, 2013, 2017). Personality was measured with the 15-item BFI-S. I created a measurement model for the BFI-S that shows measurement invariance across the four occasions (Schimmack, 2019a). I also related personality to the single-item life-satisfaction rating in the SOEP (Schimmack, 2019b). Here, I extend this analysis by taking advantage of the fourth measurement of personality in 2017, which makes it possible to separate trait and state variance in personality and well-being.

The SOEP measures life-satisfaction in two ways. First, it includes several domain-satisfaction items (health, finances, recreation, housing). Second, it includes a global life-satisfaction item. In a different post (Schimmack, 2019c), I examined the relationship between these items and found that global items are influenced by a general disposition factor and satisfaction with finances and health, while the other two domains are relatively unimportant. Based on this finding and related evidence (Zou, Schimmack, & Gere, 2013), I averaged the domain satisfaction judgments and used it as an indicator of life-satisfaction. This makes it possible to remove random measurement error from the measurement of life-satisfaction on a single occasion. I then fitted latent-trait-state (LST) models to the personality factors and the well-being factor. These models separate the longitudinal correlations into two components. A stable trait component and a changing state component. A third parameter estimates how stable state variance is over time.

There are several ways to relate personality to life-satisfaction in this model. I chose to predict life-satisfaction variance on each occasion to the personality variances on the same occasion. The model indirect function can then be used to examine how much of the variance is due to stable personality traits or due to personality states.

The availability of four waves of data also makes it possible to model stability of the residual variances in personality items. Typically, these residuals are allowed to correlate to allow for item-specific stability, but the use of correlated residuals makes it impossible to relate this variance to other constructs. With four waves, it is possible to fit an LST model to item-residuals. Exploration of the data showed that the neuroticism item “worry” showed consistent relationships with well-being. Thus, I fitted an LST model to this item and allowed for an influence of worry on life-satisfaction.

The synatax and the complete results are posted on OSF (SOEP.4W.B5.DSX.LS).

Results

Overall model fit was acceptable, CFI = .967, RMSEA = .019, SRMR = .030.

Trait Variance and Stability of State Variance

Table 1 shows the amount of trait variance and the stability of state variance in the personality predictor variables. A more detailed discussion of the implications of these results for personality research can be found elsewhere (Schimmack, 2019a). The results for the Big Five serve as a comparison for the trait variance in life-satisfaction.

	Trait	Stability	1Y-Stability
Neuroticism	0.69	0.38	0.79	0.56
Extraversion	0.74	0.38	0.78	0.51
Openness	0.71	0.34	0.76	0.53
Agreeableness	0.68	0.20	0.67	0.57
Conscientiousness	0.60	0.29	0.73	0.64
Halo	0.60	0.36	0.78	0.63
Acquiescence	0.34	0.11	0.58	0.81
Worry	0.64	0.52	0.85	0.60

Table 2 shows how life-satisfaction at each time point is related to personality predictors. For model identification purposes, it is necessary to fix one relationship to zero. I used openness because meta-analysis show that it is the weakest predictor of life-satisfaction (Steel et. al., 2008). I did not impose constraints across the four waves.

	LS-T1	LS-T2	LS-T3	LS-T4
Neuroticism	-0.29	-0.27	-0.27	-0.26
Extraversion	0.08	0.07	0.08	0.09
Openness	–	–	–
Agreeableness	0.08	0.05	0.04	0.03
Conscientiousness	0.04	0.04	0.04	0.04
Halo	0.19	0.28	0.24	0.26
Acquiescence	0.18	0.08	0.12	0.16
Worry	-0.35	-0.34	-0.35	-0.33

The results show that out of the Big Five, neuroticism is the only notable predictor of life-satisfaction with a moderate effect size (r = -.26 to -.29). A notable finding is that extraversion is a weak predictor of life-satisfaction (r = .07 to .09). This finding is inconsistent with Costa and McCrae’s (1980) model. The results for agreeableness and conscientiousness are also weak. This finding is inconsistent with meta-analysis and with McCrae and Costa’s (1991) suggestion that high agreeableness and conscientiousness are also instrumental for higher life-satisfaction. Both halo and acquiescence bias are stronger predictors of life-satisfaction judgments than extraversion, agreeableness, and conscientiousness. Another notable finding is that the worry-facet of neuroticism is the strongest personality predictor; even stronger than the neuroticism factor (rs = -.33 to -.35). This finding is consistent with previous studies that facets of neuroticism and extraversion are better predictors of life-satisfaction than the global factors (Schimmack, Oishi, Funder, & Furr, 2004).

Table 3 shows how much of the variance in life-satisfaction is explained by trait factors that remain stable over time.

	LS-T1	LS-T2	LS-T3	LS-T4
Neuroticism	0.05	0.05	0.05	0.05
Extraversion	0.00	0.00	0.00	0.01
Openness	–	–	–	–
Agreeableness	0.00	0.00	0.00	0.00
Conscientiousness	0.00	0.00	0.00	0.00
Halo	0.02	0.04	0.03	0.04
Acquiescence	0.01	0.00	0.00	0.01
Worry	0.08	0.08	0.08	0.07
Unexplained	0.38	0.38	0.38	0.38
Total	0.55	0.56	0.56	0.55

Given the weak effects of extraversion, agreeableness, and conscientiousness, it is not surprising that these Big Five traits explain less than 1% of the variance in life-satisfaction judgments. The only notable predictor is neuroticism, which explains 5-6% of the variance. In addition, the worry facet of neuroticism is an even stronger predictor of trait variance in life-satisfaction. This finding shows that more specific traits below the Big Five add to the prediction of life-satisfaction (Schimmack, Oishi, Furr, & Funder, 2004). Halo adds only 2% and acquiescence only 1%. By far the largest portion of the trait variance was unexplained with 41% of the variance. Combined this implies that approximately half of the variance in life-satisfaction is trait variance. This finding is consistent with estimates in a meta-analysis and other analyses of the SOEP data (Anusic & Schimmack, 2016; Schimmack, Krupp, Wagner & Schupp, 2010). The estimate of 55% trait variance is also smaller than the estimate of 70% trait variance in the Big Five personality traits. This finding is also consistent with meta-analytic comparison of personality and well-being measures (Anusic & Schimmack, 2016).

Table 4 shows the results for the state-predictors of life-satisfaction. Once more extraversion, agreeableness, and conscientiousness predict less than 1% of the variance. This time, neuroticism and worry are also relatively weak predictors because most of the relationship for this traits stems from the stable component. However, the results suggest that some changes in neuroticism and worry are related to changes in life-satisfaction. However, most of the state variance in life-satisfaction is not explained by the personality predictors (33% out of 44%).

	LS-T1	LS-T2	LS-T3	LS-T4
Neuroticism	0.02	0.02	0.02	0.02
Extraversion	0.00	0.00	0.00	0.00
Openness	–	–	–	–
Agreeableness	0.00	0.00	0.00	0.00
Conscientiousness	0.00	0.00	0.00	0.00
Halo	0.01	0.03	0.02	0.03
Acquiescence	0.02	0.00	0.01	0.02
Worry	0.04	0.04	0.04	0.04
Unexplained	0.33	0.34	0.34	0.34
Total	0.44	0.44	0.44	0.45

Conclusion

These results challenge Costa and McCrae’s (1980) model of personality and well-being in several ways. First, extraversion is not a strong predictor of the stable variance in life-satisfaction. Second, even the influence of neuroticism accounts for only 10% of the stable trait variance in life-satisfaction. Adding other Big Five predictors also does not help because they have negligible relationships with life-satisfaction. Thus, most of the trait variance in life-satisfaction remains unexplained. It is either explained by more specific personality traits than the Big Five (facets) or by stable environmental factors (e.g., income). The SOEP data provide ample opportunity to look for additional predictors of trait variance. Also, researchers should conduct studies with broader personality questionnaires to find additional predictors of life-satisfaction. Searching for these predictors is an important area of research in an area that has stagnated over the past two decades.

Costa and McCrae’s model also underestimated the importance of state-factors. State factors are highly stable over fairly long periods of times and account for 50% of the reliable variance in life-satisfaction. As the Big Five mostly reflect stable traits, they cannot account for this important variance in life-satisfaction. Schimmack and Lucas (2010) argued that these factors are environmental factors because changes in life-satisfaction are shared between spouses. Thus, changes in actual life-circumstances may contribute to state variance in life-satisfaction. Consistent with this model, spouses were more similar in domains that are shared (housing, income) than in domains that are less shared (health, recreation).

Evidently, the conclusions are based on a single German sample. As impressive as these data are, it is important to compare results across samples from different populations. At least regarding the influence of extraversion, the present results are consistent with other studies that suggest the influence of extraversion on life-satisfaction (Kim, Schimmack, & Tsutsui, 2019). The idea that extraverts are happier has been exaggerated by Costa and McCrae’s model, while their own empirical results did not warrant this claim. The reason is that psychologists often ignore effect sizes.

Implications

The present results also have implications for developmental theories of personality. The idea of development is a process with an ideal outcome. For humans, the outcome is an adult human being with optimal capabilities. A collective of personality psychologists suggested that optimal personality development results in a personality type with optimal personality characteristics. I criticized this idea and argued that there is no such thing as an optimal personality. Just like there is no optimal height as the end-goal of human growth, there is no optimal level of extraversion or conscientiousness. In clinical psychology, the key criterion of mental health is that an intervention is beneficial for a patients’ well-being. Thus, we could argue that an optimal personality is a personality that maximizes individuals’ well-being. Meta-analyses suggests that extraveted, agreeable, and conscientious people have higher well-being. Thus, it might be beneficial for individuals to become more extraverted, agreeable, and conscientious. However, the present results challenge this view. After removing the evaluative aspect of personality from the Big Five only neuroticism remains a notable predictor of well-being. Thus, the key personality trait for self-improvement is neuroticism. Not surprisingly, this is also the key aspect that is targeted in self-help books and well-being programs. Until we have a better understanding of the relationship between personality and well-being, it seems premature to propose interventions that are aimed at changing individuals’ personality. Just like personality psychologists no longer endorse conversion therapy for sexual orientation, I urge for caution in submitting individuals who are carefree and impulsive to a conscientiousness conversion program. You never know when acting on the spur of a moment is the best course of action.