Study 3 investigates whether autonomic reactivity and self-reported narrative transportation mediate the effect of narrative structure on pro-environmental behavior as well as how this relationship might be moderated by the end valence of the stimuli.

In this study, we test the expectation that narrative structure impacts pro-environmental behavior by influencing autonomic reactivity and heightened emotional arousal associated with the subjective experience of narrative transportation. To strengthen the robustness of our findings, we triangulate self-report measures of narrative transportation with measures of autonomic reactivity using a further reduced set of naturalistic stimuli from study 2. We predict that the influence of narrative structure on behavior is mediated by physiology, which is in turn moderated by the emotional valence of a video’s ending and narrative transportation.

Methods and materials

In a within-subjects, repeated-measures design, we pared down the stimuli list to six videos (Appendix K), selecting those with three highest and lowest mean narrative transportation scores as well as the following elimination criteria: (1) all videos should be produced by non-profit organizations; (2) no producer should have more than one video in the final stimuli set so as to preclude the possibility of repetition; (3) videos should not specifically mention localities outside of the USA; (4) video duration was limited to a maximum 195 s so as to limit noise attributable to attentional variation between individual stimuli and to accommodate attentional constraints in an experimental setting.

Sessions were conducted at the lab of an American university, and 87 participants were recruited (53% female) from the surrounding community through mass e-mails and an existing online recruitment pool (ages 18–24 (55.8%), 25–34 (32.5%), 35–44 (7%), 45–54 (3.5%), 55–64 (1.2%)). The sample size was determined beforehand in line with recommendations by Simmons et al. (2011) and Quintana (Quintana 2017). An Institutional Review Board approved this study. Immediately after consent, the participants responded to a pre-treatment questionnaire containing demographic items and trait measures (Appendix L). Upon completion, the participants were fitted with sensors, escorted to a private lab room, and seated in front of a laptop computer outfitted with headphones. All proceeding tasks, including the donation task, were presented in Psychopy (Peirce 2009). A research assistant was seated on the opposite side of a privacy curtain throughout the duration of the study.

To gauge affective engagement and emotional arousal, we employ non-invasive measures of reactivity in the autonomic nervous system (ANS). Inter-beat (RR) intervals measure the number of milliseconds between R peaks in the QRS complex of the ECG wave. Closely associated with RR intervals, high-frequency heart rate variability (HF-HRV) is calculated with the RR interval over a period of time using an algorithm known as the fast Fourier transform. Because the heart is dully innervated, cardiac measures such as HF-HRV and RR intervals generally indicate both sympathetic and parasympathetic reactivity with HF-HRV reflecting greater parasympathetic control of the heart (Potter and Bolls 2012). Electrodermal activity (EDA) measures changes in skin conductance and tends to be a more “pure” measure of SNS activation.

After a 5-minute baseline acquisition period for ANS measures of cardiac activity and skin conductance (see Appendix M for more detail), the participants viewed all videos presented in a random order. Autonomic activity was recorded continuously throughout the entire session. The participants were given a base compensation fee of USD 29 and the opportunity to earn an additional USD 1 per video. These additional dollars were our dependent variable in a donation task similar to that designed by Xygalatas et al. (Xygalatas et al. 2016). Additional earnings were given to participants in the form of 100 pennies in a clear plastic container labeled “earnings,” and placed next to an empty, but otherwise identical, container labeled “donations.” Post-video stimulus, the participants could voluntarily donate a portion of this dollar to the producer of the climate change video they had just viewed. The participants were instructed to pour the amount they wished to donate from the “earnings” cup to the “donations” cup without touching the coins or counting.

Upon the completion of the task, the participants notified the research assistant who removed both containers, privately weighing and recording donations out of the participant’s purview. The participants were then asked to answer five items designed to assess self-reported narrative transportation (Appel et al. 2015), and two items to gauge narrative familiarity and attention. This process was repeated for each of the six stimuli, after which time all sensors were removed, and participants were escorted to another room where they completed a final questionnaire containing additional demographic, state, and trait measures. After finishing the last survey, the participants were privately paid their earnings, minus any donations, and dismissed. The donations were sent to the video producers at the conclusion of the study.

To examine the relationships between narrative structure and pro-environmental behavior, including mediators of autonomic reactivity (EDA, HF-HRV, and RR intervals), moderated by residual valence, and the unmoderated mediator of self-reported narrative transportation, we performed a conditional process and linear mixed effects analyses, using R Studio (Team 2012) and lme4 (Bates et al. 2015). Six participants were considered outliers or excluded from analysis for one or more of the following reasons: skin conductance levels ≥ 3 SD from the mean (Sokol-Hessner et al. 2009), cardiac activity ≥ 4 SD from the mean (Potter and Bolls 2012), or missing data, leaving a total of 81 participants for final analysis. The ∆BIC scores were generated for all models, and the model with the lowest ∆BIC was selected as the most predictive. In cases where the ∆BIC of models was ≤ 2, the most parsimonious model was selected.

Results

As can be seen from Table 1, we observed a direct effect of narrative structure on one measure of cardiac activity, RR intervals (a 3 = 0.031). There was a conditional indirect effect of narrative structure on pro-environmental donation behavior, mediated by a 3.1% increase in inter-beat intervals (RR), compared with baseline, moderated by negative residual valence, Cohen’s d = 0.021 (b 8 = − 79.723). The results presented in Table 1 are conveyed in a more intuitive way in Fig. 3. This diagram depicts the statistical representation of the conceptual model showing expected paths, together with the coefficients. Our final model provides no evidence that narrative structure predicts behavior through self-reported narrative transportation or alterations in the other autonomic measures, electrodermal activity (EDA), or heart rate variability (HF-HRV).

Table 1 Main results on the effect of narrative structure on pro-environmental behavior Full size table

Fig. 3 Statistical diagram with results Full size image

Although our primary aim with this study is not to investigate a direct relationship between narrative structure and donations, we include the path in our conditional process analyses, as recommended by Hayes (2013). Subsequent analysis revealed no direct effect between narrative structure and pro-environmental behavior, nor do we find self-reported narrative transportation results to be predictive of donation behavior. The results of the analysis using the pruned model (Appendix N) following the Hayes (2013) method serve as a robustness check and can be seen in Appendix O.

Discussion

Study 3 provides empirical support for our proposition that climate change narratives structured as stories stand a better chance than analytical narratives at influencing pro-environmental behavior through heightened emotional arousal. Indeed, climate change stories with negatively valenced endings influenced pro-environmental behavior by increasing inter-beat (RR) intervals. Inferences about psychophysiology should always be made with caution, and RR intervals are one of the more difficult autonomic measures to interpret because the cardiac activity is influenced by both the sympathetic (SNS) and parasympathetic (PNS) branches of the autonomic nervous system. These systems are comprised of motor neurons that control the organs and glands, and can be coactive (Berntson et al. 1993) or decoupled (Potter and Bolls 2012). The SNS facilitates energy expenditure and, when activated, prepares the body for fight, flight, and procreation. It prepares to mobilize the body to confront threats through physiologic changes such as an increase in heart rate and blood pressure. The PNS facilitates recovery and energy storage through rest, repair, and digestion. SNS and PNS reactivity can operate independently or orthogonally, and both are indicative of attention and affective engagement (Barraza et al. 2015). Although our measure is likely under the influence of multiple patterns of ANS activity, it is clear that negatively valenced stories resulted in cardiac deceleration, which in turn predicted behavior.

Fluctuations in cardiac activity have been associated with attentional allocation (Potter and Bolls 2012) and emotional arousal (Mitkidis et al. 2015), and key determinants of empathic and sympathetic responses (Dickert and Slovic 2009). Stereotypical threat states and emotional arousal generally result in acceleration in heart rate and decrease in RR intervals, as a result of SNS reactivity (Potter and Bolls 2012). Climate change, however, lacks a number of salient characteristics which typically trigger our cerebral alarms in the face of danger. Because the danger does not feel immediate or proximal, it provokes a different type of reactivity compared with threats which activate sympathetic arousal. Given that we observed no effect in the “purer” measure of sympathetic activation (EDA), the finding that cardiac deceleration predicts behavior suggests predominantly PNS reactivity. PNS activation has been associated with the orienting reflex (Graham and Clifton 1966), increased the allocation of cognitive resources in the form of attention and interest (Potter and Bolls 2012), and the encoding of information into working memory (Potter and Bolls 2012).

Our finding is in line with the information intake-rejection hypothesis, which posits that parasympathetic activation improves response effectiveness by enhancing the ability to encode meaningful information from an individual’s environment into working memory (Lacey and Lacey 1974). These results may indicate a bodily state of “vigilant readiness,” a preparatory response pattern akin to a predator stalking its prey (Lang and Bradley 2010): attentive and observant, weighing the options. This aligns with a prior work proposing a relationship between negative emotional valence and heart rate deceleration (Bolls et al. 2001; Lang et al. 1996) as well as increased autonomic arousal (Potter and Bolls 2012). Negative valence has been shown to have a more enduring effect on heart rate response compared with positive emotion (Brosschot and Thayer 2003), which may help explain why participants who experienced cardiac deceleration also exhibited increased pro-environmental behavior.

Although it is difficult to disentangle emotional arousal and cognitive processing, our finding that heart rate deceleration leads to increased pro-environmental behavior likely reflects emotional arousal in tandem with cognitive processing, culminating in a calculated form of autonomic response to a distal threat. It is noteworthy that analytical narratives did not evoke this same autonomic response. We posit that, unlike stories, these informational narratives do not effectively aid the construction of emotion which, in complement, signals the brain to take action to optimize bodily budgets.