Personality changes associated with increasing environmental concerns

Christopher J. Hopwood, Ted Schwaba, Wiebke Bleidorn University of California, Davis

Contact: [email protected]

Acknowledgements

The authors thank the German Institute for Economic Research for making the data available for this project. We have no funding sources or conflicts of interest to report. 2 Personality Change Environmental Concern

Abstract

Personal concerns about climate change and the environment are a powerful motivator of sustainable behavior. People’s level of concern varies as a function of a variety of social and individual factors. Using data from 58,748 participants from a nationally representative German sample, we tested preregistered hypotheses about factors that impact concerns about the environment over time. We found that environmental concerns increased modestly from 2009-2017 in the German population. However, individuals in middle adulthood tended to be more concerned and showed more consistent increases in concern over time than younger or older people. Consistent with previous research, Big Five personality traits were correlated with environmental concerns. We present novel evidence that increases in concern were related to increases in the personality traits neuroticism and openness to experience. Indeed, changes in openness explained roughly 50% of the variance in changes in environmental concerns. These findings highlight the importance of understanding the individual level factors associated with changes in environmental concerns over time, towards the promotion of more sustainable behavior at the individual level.

Keywords

Sustainability, Environment, Climate Change, Personality Traits, Personality Development 3 Personality Change Environmental Concern

Climate change poses an existential threat to humankind. Sustainable behavior at the individual level is a primary tool for promoting environmental health (Chuang et al., 2020; Osbaldiston & Schott, 2012). However, sustainable behavior requires changes in habits and norms that are often uncomfortable, inconvenient, and costly, and thus unwelcome by many individuals, institutions, and societies (Aragon- Correa et al., 2020; Hall et al., 2018; Weber, 2015). As a result, success has been uneven thus far, and the threat persists.

Key to addressing this challenge is a better understanding of the factors that motivate or prevent sustainable behavior. Many types of sustainable behavior reflect a variety of personal decisions and sacrifices, such as taking the time to recycle, using alternative and potentially less convenient modes of transportation, foregoing goods with a substantial carbon footprint, or paying more money for sustainable products. People differ in their preferences and willingness to make such decisions and sacrifices. Thus, considerable potential lies in a greater understanding of the personal factors that promote or impede sustainable behaviors (Freeman et al., 2020; Hirsch, 2010; Soutter et al., 2020).

One critical factor is personal concern. People are motivated to make sacrifices and change their behavior when they are concerned that their behavior has negative consequences (Hennecke et al., 2014; Liberman & Trope, 1998). It follows that increases in concerns about the environment promote more sustainable behavior (Figure 1; Barnett et al., 2019; Binder & Blankenburg, 2016; Jekria & Daud, 2016; West et al., 2018). But what heightens concern about the environment?

There is robust evidence that people with certain personalities are more likely to be concerned about the environment (Hirsch, 2010; Milfont & Sibley, 2012; Weber, 2010) and engage in sustainable behavior (Soutter et al., 2020). In a previous cross-sectional study, Hirsch (2010) found positive associations with four personality traits: neuroticism, openness, agreeableness, and conscientiousness. These findings, depicted in Figure 1, suggest that environmental concern is higher among people who experience more negative emotions and stress, seek out novel information and experiences, are tender-hearted and sensitive to others’ well-being, and feel responsible and motivated, respectively.

Notably, existing studies on personality traits and environmental concerns have relied on cross-sectional designs to determine whether and to what degree individuals with certain personalities are more concerned about the environment at one point in time. This design precludes an examination of the processes underlying personality and environmental concerns. There is an essential difference between how people are different from one another at one point in time, and how they experience lasting changes via interactions with the world around them as their lives progress. Moreover, cross-sectional effects are prone to influences of third variables that are less likely to affect longitudinal associations. To understand the process depicted in Figure 1, researchers need to track links between changes in personality and changes in environmental concerns over time. Knowledge about the connection between how people grow, change, and mature and how these changes are related to their concerns about the environment could provide key insights about pathways to motivate sustainable behavior at the individual level.

It is established that personality traits change over time (Roberts, Walton, Viechtbauer, 2006), and that some people change more than others (Schwaba & Bleidorn, 2018). There is also evidence that variation in personality changes depends in part on certain experiences (Bleidorn et al., 2018, Luo et al., 2017), including large-scale social-environmental changes. We thus predicted dynamic links between changes in environmental concerns and changes in personality. We expected that changes in the traits that have been associated with concerns about the environment in cross-sectional studies (Hirsch, 2010; Soutter et al., 2020) – neuroticism, conscientiousness, agreeableness, and openness – would be positively associated with changes in environment concerns (Figure 1).

In summary, the goal of this pre-registered study is to go beyond cross-sectional evidence and examine the co-development of personality traits and environmental concerns. We used longitudinal data from a nationally representative sample of nearly 60,000 German participants whose concerns about the environment and climate change were assessed biannually from 2009 to 2017, and whose personality traits were assessed three times during that span. We tested whether people have become increasingly 4 Personality Change Environmental Concern more concerned about environmental issues over the past decade, and whether people who experienced the most pronounced increases showed corresponding changes in personality traits.

Materials and Methods

The preregistration for this study can be found at https://osf.io/fhqja/. We used data from the German Socioeconomic Panel (GSOEP; Wagner et al., 2007), which included 58,748 participants who provided 310,743 total yearly measurements. The sample was 53% female and the average age was 48.06 years (SD = 17.35).

Concern for the environment and concern for climate change were measured annually with single items, rated on a 3-point scale ranging from “not concerned at all” to “very concerned”. Personality traits were measured in 2009, 2013, and 2017 with the 15-item version of the Big Five Inventory-S (Gerlitz & Schupp, 2005), which measures the personality traits extraversion, agreeableness, conscientiousness, neuroticism, and openness. Each trait scale has three items. Coefficient alphas ranged from .48-.67; omega total values ranged from .55-.70 (Table S1). This abbreviated measure has demonstrated measurement invariance across age groups (Brandt et al., 2020) and measurement occasions (Specht et al., 2011).

Socioeconomic status (SES) was computed at each participant’s first measurement wave using the International Socio-Economic Index of occupational status (ISEI), derived from the International Standard Classification of Occupations (ISCO), using data on occupation, parental education, and income (Ganzeboom et al., 1992). Cohorts were defined by decade. Age cohort sample sizes were as follows: 270 were born in the 1910s or earlier, 1920s (1,712), 1930s (4,427), 1940s (5,655), 1950s (7,892), 1960s (11,884), 1970s (11,339), 1980s (9,552), 1990s or later (6017). Education was computed as the maximum educational attainment across all measurement occasions provided by a participant; the average participant completed upper secondary education (see Tables S2 and S3 for descriptive information about study variables).

Analyses were conducted in R (R core team, 2015), with structural equation models estimated using the lavaan package (Rosseel, 2012) and visualized using ggplot2 (Wickham, 2015). Using Full Information Maximum Likelihood estimation to handle missing data, we fit linear univariate latent growth curve models to characterize change in both environmental concern variables (9 waves of data) and all five personality traits (3 waves of data; Figure S1). These models fit well to the data (RMSEAs <= .046, CFIs >= .971). We then fit bivariate latent growth curve models in order to examine correlates between latent slope and intercept factors (Tables S4, S5). These models again fit well to the data (RMSEAs <= .046, CFIs >= .971). Finally, we added time-invariant covariates of age at study entry, SES, sex, and highest level of education achieved during the study period to the models to examine the persistence of hypothesized effects with these variables controlled (Table S6, Figure S2).

Results

The average person in our sample reported being slightly more than “somewhat concerned” about both climate change and the environment. On average, these concerns increased slightly from 2009-2017 (Figure 2; Cohen’s d between 2009 and 2017 was about .10 for both variables). Univariate growth curve models fit the data well and confirmed significant but modest increases for both concern about the environment (b = .002 per year, p <.001, 95% CI [.001,.003]) and concern about climate change (b = .007 per year, p <.001, 95% CI [.006,.008]).

However, we also found that these relatively flat trajectories masked underlying variability as a function of age, both within individuals and between cohorts. Figure 3 depicts concerns across different ages, both for the entire sample at the 2009 assessment and for individual cohorts across all assessment waves. Individuals in middle to late adulthood expressed the most concerns about both environmental issues and climate change, whereas younger and older individuals were relatively less concerned. Moreover, cohorts born between 1940 and 1990 experienced relatively sharp increases across assessment waves, whereas those born before 1940 or after 1990 showed decreases in concern over time. Thus, relatively modest 5 Personality Change Environmental Concern increases in concern about the environment at the aggregate level were masked by systematic across age cohorts and stronger increases as a function of age within age cohorts.

Over the course of the study period, we found significant mean-level changes in people’s personality, as evidenced by increases in extraversion (B = .004 per year, p <.001, 95% CI [.003,.006]) and openness (B = .011 per year, p <.001, 95% CI [.010,.012]) and decreases in conscientiousness (B = -.009 per year, p <.001, 95% CI [-.010, -.007]) and neuroticism (B = -.009 per year, p <.001, 95% CI [-.011, -.009]). Mean levels of agreeableness remained stable (B = .001 per year, p = .059, 95% CI [-.000,.003]). Critically, people’s personalities changed differently from one another: we found significant (p < .001) individual differences in change across all study variables (b = .0015 - .0020) enabling tests of longitudinal association between environmental concerns and personality.

Our primary goal was to test pre-registered hypotheses about the cross-sectional and longitudinal associations between personality traits and environmental concerns. Bivariate latent growth curve models that included the trajectories of both personality traits and environmental concerns fit the data well. We predicted cross-sectional and longitudinal associations between both environmental concern variables and higher agreeableness, conscientiousness, neuroticism, and openness. As shown in Table 1, intercept (i.e., cross-sectional) correlations were significant for all five personality traits, including the four that were hypothesized as well as higher extraversion.

Changes in environmental concerns, however, were only significantly related to changes in two traits, neuroticism and openness. These effects held when controlling for plausible third-variable effects of age, SES, sex, and education. Co-development between environmental concerns and openness declined in magnitude but remained strong (rs = .69 and .66) when including these covariates, indicating that SES and education play some role in this co-development. Overall these effects indicate that nearly half of the variance in increases in environmental concerns over time were explained by increases in openness, whereas about 17% were explained by increases in neuroticism. The replication of this pattern of effects across two indicators of environmental concern strengthened confidence in these results.

There were also some unpredicted significant correlations in these models between intercepts and slopes. Specifically, people who were more concerned about the environment on average tended to become more neurotic, less agreeable, and less conscientious over time, whereas people who were more neurotic tended to become less concerned about the environment.

Discussion

Personal concern is a potent motivator for individual action, and individual action is a powerful tool in the fight against climate change. We found that participants from a large representative German sample are significantly concerned about climate change and the environment, that these concerns increased over the past decade, and that these increases were sharper for some people than for others. People’s age, cohort, and personality traits all helped explain these differences; the single largest preregistered effect indicated that as people become more open to experience, they also become more concerned about the environment.

Interpretations of the trajectory of environmental concerns over time are complicated by the distinct impacts of the general passage of time, individual aging processes, and generational cohort effects. There were modest increases in environmental concerns over time, on average. However, individuals between the ages of 40 and 80 had higher levels of concern than individuals on either the younger or older tails of the age distribution (Figure 3). This pattern corresponds to the results reported in a study of changes in environmental concern across 33 countries over a similar period of time (Franzen & Vogle, 2013). Moreover, whereas individuals in these middle cohorts tended to experience increasing levels of concern from 2009-2017, younger and older age groups exhibited a mix of trajectories, including decreases in some age groups (Figure 3).

This study replicated previous cross-sectional studies indicating that personality traits are strong predictors of environmental concern (Hirsch, 2010), as well as other sustainability-related attitudes and 6 Personality Change Environmental Concern behaviors (Milfont & Sibley, 2012; Soutter et al., 2020). Findings from this study suggest that personality might represent an avenue for personalizing sustainability interventions based on individual concerns and values (Anagnostopoulou et al., 2018). For example, conscientious people might be most driven to engage in sustainable behavior by their sense of responsibility, agreeable people by their desire to do good for others, and neurotic people by their anxieties about future threat. Information about individuals’ personalities could be used to tailor policies designed to promote sustainable behavior that takes peoples’ personal priorities, attitudes, and motives into account.

Importantly, our results provide new evidence that changes in personality traits track with changes in environmental attitudes and behaviors. Increases in openness explained approximately half the variance in increases in environmental concerns, even with demographic factors controlled. Individuals who are more open to experience tend to be interested in aspects of the environment outside of themselves, positively disposed to progressive values and causes, and oriented towards future possibilities (McCrae & Sutin, 2009). As people become more open over time, they may become more aware of the impacts of climate change, more likely to consider a future world impacted by climate change, and thus more concerned. As such, promoting openness may be a potent pathway for fostering sustainable behavior. Conversely, increasing levels of concern may lead to greater consideration of new possibilities about where to live or how to change behavior to be more sustainable. Thus, increasing concerns about climate change could provoke a more serious reflection about how to effectively respond, as indicated by greater openness.

We also found that people who became more neurotic over time showed corresponding increases in environmental concerns. Neuroticism involves a tendency to experience negative emotions such as anxiety, depression, and anger, all of which are understandable consequences of awareness of the climate crisis. These findings suggest that rising concerns about the environment are associated with increasingly unpleasant emotions. As neuroticism is a strong predictor of psychopathology (Lahey, 2009), our findings further suggest a possible connection between environmental issues and mental health (Berry et al., 2010). At a more normative level, sub-clinical anxiety may promote behavior change, and thus individual increases in neuroticism, for example via information about the threat posed by climate change, may be one avenue towards more sustainable behavior.

Findings of longitudinal associations between environmental concerns and increasing openness and neuroticism raise questions about causality. If changes in personality cause changes in concern, and ultimately behavior, personality interventions could help promote sustainable behavior and other prosocial outcomes (Hudson & Fraley, 2015; Steiger et al., 2018), particularly when connected to tractable, practical models of sustainability (Clark et al., 2016). It is also possible that changes in concern about the environment cause changes in personality. This finding would provide important information about the factors that impact personality development (Roberts et al., 2017), an issue with important implications for a variety of public policy issues (Bleidorn et al., 2019).

Conclusion

Concerns about the environment have been increasing somewhat in the German population over the last decade, but this general trend masks larger increases within age cohorts, particularly among middle-aged adults. We replicated the finding that concerns about climate change are consistently related to a range of personality traits, and presented novel evidence that increases in the personality traits openness and neuroticism have strong associations with increases in environmental concerns, even with age, education, sex, and SES controlled. These findings highlight personal factors associated with increases in environmental concerns that may provide viable pathways to promoting sustainable behavior at the individual and societal levels. 7 Personality Change Environmental Concern

References

Anagnostopoulou, E., Bothos, E., Magoutas, B., Schrammel, J., & Mentzas, G. (2018). Persuasive technologies for sustainable mobility: State of the art and emerging trends. Sustainability, 10, 2128.

Aragon-Correa, J. A., Marcus, A. A., & Vogel, D. (2020). The effects of mandatory and voluntary regulatory pressures on firms’ environmental strategies: A review and recommendations for future research. Academy of Management Annals, 14(1), 339-365.

Barnett, M. D., Archuleta, W. P., & Cantu, C. (2019). Politics, concern for future generations, and the environment: Generativity mediates political conservatism and environmental attitudes. Journal of Applied Social Psychology, 49(10), 647-654.

Berry, H. L., Bowen, K., & Kjellstrom, T. (2010). Climate change and mental health: a causal pathways framework. International Journal of Public Health, 55, 123-132.

Binder, M., & Blankenberg, A. K. (2016). Environmental concerns, volunteering and subjective well-being: Antecedents and outcomes of environmental activism in Germany. Ecological Economics, 124, 1-16.

Bleidorn, W., Hill, P. L., Back, M. D., Denissen, J. J., Hennecke, M., Hopwood, C. J., ... & Orth, U. (2019). The policy relevance of personality traits. American Psychologist, 74(9), 1056-1067.

Bleidorn, W., Hopwood, C. J., & Lucas, R. E. (2018). Life events and personality trait change. Journal of Personality, 86(1), 83-96.

Brandt, N. D., Becker, M., Tetzner, J., Brunner, M., Kuhl, P., & Maaz, K. (2020). Personality across the lifespan: Exploring measurement invariance of a Short Big Five Inventory from ages 11 to 84. European Journal of Psychological Assessment, 36, 162–173.

Chuang, F., Manley, E., & Petersen, A. (2020). The role of worldviews in the governance of sustainable mobility. Proceedings of the National Academy of Sciences, 117, 4024-4042.

Clark, W. C., Van Kerkhoff, L., Lebel, L., & Gallopin, G. C. (2016). Crafting usable knowledge for sustainable development. Proceedings of the National Academy of Sciences, 113(17), 4570-4578.

Franzen, A., & Vogl, D. (2013). Two decades of measuring environmental attitudes: A comparative analysis of 33 countries. Global Environmental Change, 23(5), 1001-1008.

Freeman, J., Baggio, J. A., & Coyle, T. R. (2020). Social and general intelligence improves collective action in a common pool resource system. Proceedings of the National Academy of Sciences, 117(14), 7712-7718.

Ganzeboom, H. B., De Graaf, P. M., & Treiman, D. J. (1992). A standard international socio-economic index of occupational status. Social science research, 21, 1-56.

Gerlitz, J. Y., & Schupp, J. (2005). Zur Erhebung der Big-Five-basierten persoenlichkeitsmerkmale im SOEP. DIW Research Notes, 4, 2005.

Hall, M. P., Lewis Jr, N. A., & Ellsworth, P. C. (2018). Believing in climate change, but not behaving sustainably: Evidence from a one-year longitudinal study. Journal of Environmental Psychology, 56, 55- 62.

Hennecke, M., Bleidorn, W., Denissen, J. J., & Wood, D. (2014). A three‐part framework for self‐regulated personality development across adulthood. European Journal of Personality, 28(3), 289-299. 8 Personality Change Environmental Concern

Hirsh, J. B. (2010). Personality and environmental concern. Journal of Environmental Psychology, 30(2), 245-248.

Hudson, N. W., & Fraley, R. C. (2015). Volitional personality trait change: Can people choose to change their personality traits? Journal of Personality and Social Psychology, 109, 490–507.

Jekria, N., & Daud, S. (2016). Environmental concern and recycling behaviour. Procedia Economics and Finance, 35, 667-673.

Lahey, B. B. (2009). Public health significance of neuroticism. American Psychologist, 64, 241-256.

Liberman, N., & Trope, Y. (1998). The role of feasibility and desirability considerations in near and distant future decisions: A test of temporal construal theory. Journal of Personality and Social Psychology, 75, 5- 18.

Luo, J., Derringer, J., Briley, D. A., & Roberts, B. W. (2017). Genetic and environmental pathways underlying personality traits and perceived stress: Concurrent and longitudinal twin studies. European Journal of Personality, 31, 614-629.

McCrae, R. R., & Sutin, A. R. (2009). Openness to experience. Handbook of individual differences in social behavior, 15, 257-273.

Milfont, T. L., & Sibley, C. G. (2012). The big five personality traits and environmental engagement: Associations at the individual and societal level. Journal of Environmental Psychology, 32, 187-195.

Osbaldiston, R., & Schott, J. P. (2012). Environmental sustainability and behavioral science: Meta- analysis of proenvironmental behavior experiments. Environment and Behavior, 44(2), 257-299.

Roberts, B. W., Luo, J., Briley, D. A., Chow, P. I., Su, R., & Hill, P. L. (2017). A systematic review of personality trait change through intervention. Psychological Bulletin, 143(2), 117-141.

Roberts, B. W., Walton, K. E., & Viechtbauer, W. (2006). Patterns of mean-level change in personality traits across the life course: a meta-analysis of longitudinal studies. Psychological bulletin, 132(1), 1-25.

Rosseel, Y. (2012). Lavaan: An R package for structural equation modeling and more. Version 0.5–12 (BETA). Journal of statistical software, 48(2), 1-36.

Schwaba, T., & Bleidorn, W. (2018). Individual differences in personality change across the adult life span. Journal of Personality, 86, 450-464.

Soutter, A.R.B., Bates, T.C., & Mõttus, R. (2020). Big Five and HEXACO personality traits, proenvironmental attitudes, and behaviors: A meta-analysis. Psychological Science, 15, 913-941.

Specht, J., Egloff, B., & Schmukle, S. C. (2011). Stability and change of personality across the life course: The impact of age and major life events on mean-level and rank-order stability of the Big Five. Journal of Personality and Social Psychology, 101, 862–882.

Stieger, M., Nißen, M., Rüegger, D., Kowatsch, T., Flückiger, C., & Allemand, M. (2018). PEACH, a smartphone-and conversational agent-based coaching intervention for intentional personality change: study protocol of a randomized, wait-list controlled trial. BMC psychology, 6(1), 43.

Wagner, G. G., Frick, J. R., & Schupp, J. (2007). The German Socio-Economic Panel study (SOEP)- evolution, scope and enhancements. Journal of Applied Social Science Studies, 127: 139–69.

Weber, E. U. (2010). What shapes perceptions of climate change?. Wiley Interdisciplinary Reviews: Climate Change, 1(3), 332-342. 9 Personality Change Environmental Concern

Weber, E. U. (2015). Climate change demands behavioral change: What are the challenges?. Social Research: An International Quarterly, 82(3), 561-580.

West, S., Haider, L. J., Masterson, V., Enqvist, J. P., Svedin, U., & Tengö, M. (2018). Stewardship, care and relational values. Current opinion in environmental sustainability, 35, 30-38.

Wickham, H. (2016). Modelling for Visualisation. In ggplot2 (pp. 221-240). Springer, Cham.

10 Personality Change Environmental Concern

Figure 1. The role of personality development in environmental concerns and sustainable behavior. 11 Personality Change Environmental Concern

Figure 2. Average environmental concerns in a German representative sample from 2009-2017 (N = 58,748 participants, 310,743 assessments). 12 Personality Change Environmental Concern

Figure 3. Age trends in concern about the environment (A) and climate change (B) 2009-2017 (N = 58,748 participants, 310,743 assessments).

13 Personality Change Environmental Concern

Table 1. Co-development between personality traits and concerns about the environment and climate change.

Environmental Environment Climate Change Personality Concern Trait Parameter Parameter r p 95% CI r p 95% CI Extraversion Intercept Intercept .03 .001 [.01, .06] .06 <.001 [.04, .08] Intercept Slope .04 .135 [-.01, .09] .00 .963 [-.05, .05] Slope Intercept -.07 .101 [-.15, .01] -.09 .020 [-.17, -.01] Slope Slope -.01 .920 [-.18, .16] .12 .157 [-.05, .28] Agreeableness Intercept Intercept .16 <.001 [.14, .18] .15 <.001 [.13, .18] Intercept Slope -.07 .011 [-.13, -.02] -.08 .005 [-.13, -.02] Slope Intercept -.13 .001 [-.21, -.06] -.16 <.001 [-.23, -.08] Slope Slope .14 .102 [-.03, .30] .22 .006 [.06, .39] Conscientiousness Intercept Intercept .10 <.001 [.08, .12] .13 <.001 [.11, .15] Intercept Slope -.07 .017 [-.13, -.01] -.11 <.001 [-.17, -.06] Slope Intercept -.11 .002 [-.17, -.04] -.11 .001 [-.18, -.05] Slope Slope .07 .319 [-.07, .22] .15 .032 [.01, .29] Neuroticism Intercept Intercept .20 <.001 [.17, .22] .18 <.001 [.16, .20] Intercept Slope -.10 <.001 [-.15, -.05] -.12 <.001 [-.17, -.07] Slope Intercept -.13 <.001 [-.20, -.06] -.10 .004 [-.16, -.03] Slope Slope .45 <.001 [.30, .60] .41 <.001 [.26, .56] Openness Intercept Intercept .23 <.001 [.21, .25] .21 <.001 [.19, .23] Intercept Slope -.03 .215 [-.09, .02] -.04 .114 [-.09, .01] Slope Intercept -.10 .047 [-.20, .00] -.09 .064 [-.19, .01] Slope Slope .88 <.001 [.54, 1.00] .83 <.001 [.51, 1.00] Note. Bold font indicates significance (p < .01). 14 Personality Change Environmental Concern

Supplementary materials

Deviation from pre-registration.

We pre-registered that we would examine co-development between personality traits and concern about the environment from 2005-2017. Results of these analyses are presented in Table S4 and are very similar to results presented in the main text. To increase the commensurability of results between this variable and concern about climate change (measured from 2009-2017), we focus in the main text on analyses covering 2009 onwards, instead. 15 Personality Change Environmental Concern

Table S1. Internal consistency estimates for the BFI-S.

Alpha Extraversion Agreeableness Conscientiousness Neuroticism Openness 2009 .67 .50 .59 .62 .61 2013 .66 .48 .58 .62 .60 2017 .66 .51 .61 .59 .60 Omega total 2009 .69 .57 .66 .64 .64 2013 .69 .55 .65 .65 .63 2017 .70 .57 .68 .61 .62 16 Personality Change Environmental Concern

Table S2. Means and SDs over the entire study period.

Concern Concern about Ext. Agr. Con. Neu. Ope. about Climate Environment Change Year N M SD M SD M SD M SD M SD M SD M SD 20,03 2005 4.83 1.14 5.45 0.98 5.9 0.95 3.96 1.23 4.49 1.22 1.13 0.63 4 21,19 2006 1.13 0.62 6 19,83 2007 1.25 0.64 3 18,70 2008 1.14 0.63 2 19,75 2009 4.77 1.15 5.34 0.98 5.82 0.95 3.83 1.22 4.40 1.22 1.14 0.62 1.13 0.66 7 25,37 2010 1.17 0.62 1.11 0.68 6 26,69 2011 1.19 0.62 1.13 0.67 0 26,07 2012 1.15 0.62 1.09 0.67 8 27,82 2013 4.85 1.11 5.39 0.96 5.83 0.92 3.77 1.22 4.58 1.19 1.12 0.63 1.06 0.67 2 26,10 2014 1.12 0.64 1.08 0.68 7 25,26 2015 1.10 0.63 1.07 0.67 4 25,82 2016 1.14 0.64 1.13 0.67 9 28,05 2017 4.95 1.15 5.49 1.00 5.8 0.96 3.79 1.24 4.74 1.22 1.21 0.64 1.21 0.67 5 Note: Ext. = Extraversion. Agr. = Agreeableness. Con. = Conscientiousness. Neu. = Neuroticism. Ope. = Openness to experience. Personality scores range from 1 to 7. Environmental Concern scores range from 0 to 2. 17 Personality Change Environmental Concern

Table S3. Correlations between measures in 2009 (N = 19,757).

10 11 1. 2. 3. 4. 5. 6. 7. 8. 9. . . Personality Traits 1. Extraversion 2. Agreeableness .07 3. Conscientiousness .16 .28 -.1 -.1 -.0 4. Neuroticism 6 0 9 -.0 5. Openness .37 .11 .14 6 Environmental concerns 6. Environment .01 .07 .03 .10 .11 .7 7. Climate change .02 .07 .05 .08 .12 3 Covariates .0 .0 8. Female .09 .17 .07 .21 .05 8 7 -.1 -.0 .0 .0 9. Age 2 .07 .12 .03 9 7 5 .01 -.0 -.0 -.1 .0 .0 -.0 10. SES .03 2 4 0 .17 2 2 3 .01 -.0 -.0 -.1 .0 .0 -.1 -.0 .5 11. Education .02 3 3 0 .19 3 2 2 8 7 18 Personality Change Environmental Concern

Table S4. Co-development between personality traits and concern about the environment using concern about environment data from 2005 onwards (N =58,740).

Personalit Environmenta Trait y l Parameter Parameter r p 95% CI <.00 Ext. Intercept Intercept .07 1 [.05, .09] -.0 Intercept Slope 3 .200 [-.07, .01] -.0 [-.12, Slope Intercept 7 .003 -.02] Slope Slope .05 .202 [-.03, .13] <.00 Agr. Intercept Intercept .13 1 [.11, .16] Intercept Slope .00 .963 [-.05, .04] -.0 Slope Intercept 4 .214 [-.09, .02] Slope Slope .03 .509 [-.06, .13] <.00 Con. Intercept Intercept .06 1 [.03, .08] Intercept Slope .04 .060 [.00, .09] -.0 Slope Intercept 1 .649 [-.06, .04] -.0 Slope Slope 7 .131 [-.15, .02] <.00 Neu. Intercept Intercept .24 1 [.22, .26] -.1 <.00 [-.22, Intercept Slope 8 1 -.14] -.1 <.00 [-.17, Slope Intercept 3 1 -.08] <.00 Slope Slope .40 1 [.32, .48] Ope <.00 . Intercept Intercept .26 1 [.24, .28] -.0 <.00 [-.11, Intercept Slope 7 1 -.03] -.0 [-.13, Slope Intercept 8 .002 -.03] <.00 Slope Slope .49 1 [.40, .57] Note: Ext. = Extraversion. Agr. = Agreeableness. Con. = Conscientiousness. Neu. = Neuroticism. Ope. = Openness to experience. Bolded parameter estimates are significant at p < .01 19 Personality Change Environmental Concern

Table S5. Model fits for bivariate growth curve models.

Environmental variable Personality trait df χ² CFI RMSEA 95% CI Concern about Ext. 66 1670.11 .980 .022 [.021, .023] Environment Agr. 66 1675.75 .978 .022 [.021, .023] Con. 66 1726.79 .977 .022 [.021, .023] Neu. 66 1733.57 .978 .022 [.021, .023] Ope. 66 1681.32 .979 .022 [.021, .023] Concern about Ext. 66 2350.85 .972 .026 [.025, .027] Climate Change Agr. 66 2329.63 .971 .026 [.025, .027] Con. 66 2390.24 .970 .026 [.025, .027] Neu. 66 2373.65 .971 .026 [.025, .027] Ope. 66 2380.81 .971 .026 [.025, .027] Note: Ext. = Extraversion. Agr. = Agreeableness. Con. = Conscientiousness. Neu. = Neuroticism. Ope. = Openness to experience. df = degrees of freedom. CFI = Confirmatory Fit Index. RMSEA = Root Mean Squared Error of Approximation. 20 Personality Change Environmental Concern

Table S6. Co-developmental parameter estimates with sequentially added covariates.

Covariates Sex, Sex, Age, Sex, Age, Personality Environmental Sex Age SES SES, Education Trait Parameter Parameter r r r r p 95%CI Concern Ext. Intercept Intercept .02 .03 .03 .03 .004 [.01, .05] About Intercept Slope .04 .02 .03 .03 .371 [-.03, .08] Environment Slope Intercept -.07 -.07 -.07 -.06 .110 [-.14, .01] Slope Slope -.01 .01 .01 .00 .970 [-.16, .17] Agr. Intercept Intercept .13 .13 .13 .13 <.001 [.10, .15] Intercept Slope -.08 -.08 -.08 -.08 .033 [-.15, -.01] Slope Intercept -.11 -.10 -.10 -.08 .002 [-.13, -.03] Slope Slope .11 .11 .11 .10 .176 [-.05, .26] Con. Intercept Intercept .09 .07 .07 .07 <.001 [.05, .09] Intercept Slope -.07 -.06 -.06 -.06 .074 [-.12, .01] Slope Intercept -.12 -.10 -.10 -.10 .006 [-.18, -.03] Slope Slope .06 .02 .02 .01 .860 [-.13, .16] Neu. Intercept Intercept .17 .17 .17 .18 <.001 [.15, .20] Intercept Slope -.11 -.14 -.14 -.13 <.001 [-.20, -.06] Slope Intercept -.14 -.14 -.13 -.14 <.001 [-.22, -.07] Slope Slope .45 .45 .46 .46 <.001 [.31, .62] Ope. Intercept Intercept .23 .24 .23 .22 <.001 [.20, .24] Intercept Slope -.04 -.05 -.05 -.05 .104 [-.12, .01] Slope Intercept -.10 -.10 -.08 -.06 .065 [-.13, .00] Slope Slope .88 .85 .74 .69 <.001 [.49, .89] Concern Ext. Intercept Intercept .05 .05 .05 .05 <.001 [.03, .07] About Intercept Slope .00 .00 .00 .00 .887 [-.06, .05] Climate Slope Intercept -.10 -.10 -.10 -.09 .015 [-.16, -.02] Change Slope Slope .11 .13 .13 .13 .109 [-.03, .29] Agr. Intercept Intercept .13 .12 .12 .13 <.001 [.10, .15] Intercept Slope -.07 -.09 -.09 -.09 .016 [-.16, -.02] Slope Intercept -.14 -.13 -.13 -.10 <.001 [-.15, -.05] Slope Slope .19 .19 .19 .20 .011 [.05, .35] Con. Intercept Intercept .12 .11 .11 .11 <.001 [.09, .13] Intercept Slope -.11 -.12 -.12 -.12 <.001 [-.18, -.06] Slope Intercept -.13 -.13 -.13 -.13 <.001 [-.20, -.06] Slope Slope .14 .14 .14 .14 .056 [.00, .28] Neu. Intercept Intercept .15 .15 .15 .15 <.001 [.13, .18] Intercept Slope -.12 -.16 -.16 -.15 <.001 [-.21, -.08] Slope Intercept -.10 -.11 -.10 -.10 .006 [-.18, -.03] Slope Slope .40 .41 .43 .43 <.001 [.28, .58] Ope. Intercept Intercept .20 .21 .21 .21 <.001 [.19, .23] Intercept Slope -.04 -.05 -.06 -.08 .015 [-.14, -.02] Slope Intercept -.09 -.09 -.07 -.06 .061 [-.13, .00] Slope Slope .82 .81 .70 .66 <.001 [.47, .85] Note: Ext. = Extraversion. Agr. = Agreeableness. Con. = Conscientiousness. Neu. = Neuroticism. Ope. = Openness to experience. Rows of correlations are bolded if addition of covariates changed correlation by r = .05 or larger. p-values are bolded if addition of covariates attenuated correlation to p >.01. Correlations are presented for each covariate addition, but p-values and confidence intervals are presented only for the model with all four covariates. 21 Personality Change Environmental Concern

Figure S1: Average personality trait scores over time (N = 58,748 participants) 22 Personality Change Environmental Concern

Figure S2. Path diagram for the 10 bivariate growth curve models.

Concern Concern Concern Concern Concern Concern Concern Concern Concern ‘09 ‘10 ‘11 ‘12 ‘13 ‘14 ‘15 ‘16 ‘17

1 1 1 1 5 6 7 1 1 1 3 4 1 1 1 2 8

Enviro- Enviro- nment nment Int. Slope

Big 5 Big 5 Trait Trait Int. Slope

1 1 1 4 8

Trait Trait Trait ‘09 ‘13 ‘17

Note: Int. = intercept. Each model (10 total) examines linear co-development between one Big Five Trait and one of two environmental concern variables. Models were estimated using Full Information Maximum Likelihood to handle missing data in the lavaan package of R. Bivariate models were tested after confirming that univariate models fit well to the data according to RMSEA and CFI. All 10 bivariate models also fit the data well (RMSEAs <= .046, CFIs >= .971). The time-invariant covariates sex, age, SES, and education were added to subsequent models. Interpretation focused on the four freely-estimated paths between the latent intercept and slope variables, with particular emphasis on the slope-slope correlation, which indicates longitudinal co-development of personality traits and environmental concerns. This parameter was statistically significant for both openness and neuroticism in relation to both environmental concern variables.