1. Introduction

Explanations of the hazard mechanism and behavioral recommendations are often included in public disaster prevention communications to create an educational effect for disaster risk reduction. The educational effect of disaster educational materials has been demonstrated to enhance the theoretical disaster knowledge, which may extend to later practical skills ¹. Regarding mechanism content, earthquake education research found that understanding the underlying science reduces emotional fear and supports emotionally detached reasoning about seismic events ². Another study showed that deep comprehension of natural-phenomenon mechanisms enhances long-term conceptual risk models and facilitates schema activation during decision making ³. In the context of tsunami preparedness, mechanistic explanations have been shown to improve the accuracy of risk perception by reducing uncertainty ⁴. By contrast, behavioral recommendation content directly targets action by laying out step-by-step procedures. According to the COM-B behavior change framework—which identifies capability, opportunity, and motivation as prerequisites for any behavior—such recommendations increase self-efficacy by clarifying what people can do and what opportunities the environment affords ⁵. In crisis settings, precise behavioral instructions have been empirically linked to greater intention to evacuate after receiving a tsunami warning ⁶.

However, the effect of combining these two types of information on enhancing disaster preparedness remains unclear. The effect of combining different types of information to increase decision-making accuracy could be controversial. Previous research on information diversity indicated that higher diversity of information would result in lower accuracy and longer decision-making time, causing information overload ⁷, a mental state characterized by limited information search and retrieval strategies as well as suboptimal decisions ⁸.

The effect of combining different types of messages has been demonstrated in the field of health promotion. A previous study found that with the combination of behavioral recommendation and mechanism, additional concreteness of behavioral recommendation could further improve one’s self-efficacy ⁹, which is concerned with judgments of how well one can execute courses of action required to deal with prospective situations ¹⁰. Another study found that hybrid messages including both statistical and narrative descriptions of HPV (human papillomavirus) resulted in greater perceived risk than either one of them alone ¹¹.

Health-promotion research has also examined the understanding of the neural process underlying the effect of advertisements and persuasive messages. Existing studies have commonly suggested the involvement of cortical midline structures (CMS), such as medial prefrontal cortex (mPFC) and PCC implicated in self-referential processing. For example, antidrug advertising research showed that the mPFC and amygdala were elicited when participants were exposed to strong anti-drug ads compared to ads unrelated to drugs, which represented a correlation between persuasive effect and emotional arousal as well as executive control ¹². Another functional magnetic resonance imaging (fMRI) study found that tailored nutritional messages, compared to untailored ones, activate self-referential CmS regions, hippocampus, and angular gyrus, where activity predicts subsequent reductions in unhealthy eating behavior ¹³. A study on tobacco prevention messages concluded that activation in self-referential CmS and social processing regions during announcement exposure is associated with perceived effectiveness ¹⁴.

For natural disasters, however, the effect of combining hazard-mechanism explanations and response instructions has been poorly understood at both the behavioral or neural levels. A previous experimental study has demonstrated the effect of a set of videos combining these information types for earthquakes and tsunamis, but the effect of combination has not been examined ¹⁵. Eye-tracking research showed that 3D visual effects in disaster risk communication increase cognitive load, as indicated by more fixations and shorter fixation durations, which are linked to reduced knowledge retention ¹⁶. Yet, there is no existing study that directly investigates the neural mechanisms underlying the disaster communication’s educational effect.

In this paper, we aimed to understand the effects of combining hazard-mechanism explanations and response instructions on preparedness for natural disasters by testing behavioral changes after video viewing and exploring neural correlates during viewing. We presented university students with videos conveying one of these two types of messages in the context of earthquake–tsunami disaster-risk reduction. We compared the educational effect of the videos between the group who saw either type of video alone and those who saw both types of videos. The educational effect was evaluated at the behavioral level using a scenario-based evacuation decision-making task and at the neural level using fMRI. Our analysis was non-directional with respect to the relative effectiveness of the two video types, while at the neural level we expected higher involvement of self-referential CmS for a more effective condition.

In addition to examining the behavioral and neural effects of combining mechanism explanations and evacuation instructions, it is also important to consider the cognitive characteristics of each message type. Understanding an earthquake-induced tsunami mechanism requires spatial reasoning and the integration of geographical structural knowledge. Prior research indicates that such spatial-geophysical comprehension relies on medial temporal and posterior parietal systems, including the parahippocampal region, posterior cingulate cortex (PCC), and superior parietal lobule (SPL) ^17,18. In contrast, interpreting the necessity of evacuation behavior involves crisis-management reasoning in ambiguous social contexts, drawing on CmS associated with evaluative decision making as well as temporal-parietal regions essential for social cognition ^19,20,21. Considering these theoretically grounded differences, the present study additionally analyzed neural responses to mechanism-only and evacuation-only tsunami videos using standard whole-brain voxel-wise analysis. These analyses provide a reference framework for interpreting the neural processes engaged by each message type and for understanding how combining them may alter the processing patterns elicited by single-message content. We expected that the neural pattern between the two types of videos would show share areas, like the CmS, while each type would also present unique brain regions, aligning with previous research.

2. Methods

2.1. Participants

62 undergraduate and graduate students (25 female, 37 male, mean age SD = \(20.9 \pm 2.0\)years) were recruited via email and pseudo-randomly assigned into four groups. (See Sections 2.3 and 3.1 for details). None of the participants had any history of mental disorders. Written informed consent was obtained from all participants prior to their participation. This study was approved by the ethics committee of the Smart Aging Research Center, Tohoku University, Japan (approval number: 2407-01).

3. Result

3.2. Educational Effect

Figure 2 shows the increased evacuation rate in four groups. The one-way ANOVA revealed a significant main effect of group on increased evacuation intention (\(F(3, 41) = 3.21\), \(p = 0.033\), \(\eta^2 = 0.19\)). Tukey’s HSD post-hoc tests indicated that the Evac group showed a greater increase than the Cont group (\(p = 0.030\)), whereas all other contrasts were non-significant (\(p\)s \(\ge 0.13\)).

3.3. Effect of Single Video-Type

In the one-sample \(t\)-test analysis of brain activity during Tm videos, significant activation was observed in the left and right superior parietal lobules (LSPL and RSPL), parahippocampal gyrus (PHG) and PCC (Table 1, Fig. 3(A)). In contrast, the one-sample \(t\)-test for Te videos revealed robust activation in the left and right lingual gyrus (LLG and RLG), left and right superior temporal gyrus (LSTG and RSTG), and PCC (Table 1, Fig. 3(C)). In the two-sample \(t\)-test, the Mech \(>\) Evac contrast showed significantly greater activation in regions including the SPL and inferior temporal gyrus (ITG) (Table 1, Fig. 3(B)). The Evac \(>\) Mech contrast showed significantly greater activation in regions including PCC, LSTG and RSTG (Table 1, Fig. 3(D)).

3.5. Correlation with the Educational Effect

Since a significant negative effect of video-type combination on neural response was identified for the Te movies, we examined if this is related to the educational effect, as a pot-hoc ROI analysis, pooling the data from Evac and Comb groups. Significant positive effect of the educational effect was identified for the PCC (standardized \(\beta = 0.20\), \(t(17) = 2.52\), \(p = 0.01\); Fig. 5). The effect was not significant for the other four regions: LSTG (\(\beta = 0.23\), \(t(17) = 0.25\), \(p = 0.40\)), RSTG (\(\beta = 0.20\), \(t(17) = 0.21\), \(p = 0.40\)), RLG (\(\beta = 37\), \(t(17) = 0.82\), \(p = 0.21\)), and IOG (\(\beta = 0.58\), \(t(17) = 0.28\), \(p = 0.39\)).

4. Discussion

The present study investigated the educational effectiveness of combining hazard-mechanism explanations and evacuation instructions in tsunami-related video messages, evaluating both behavioral outcomes and neural correlates. In educational effect analysis, the increases in evacuation rate showed an overall group difference, with a significant difference between the Evac and Cont groups, confirming that the tsunami evacuation instruction videos have an educational effect. However, this effect was not significantly different across other comparisons. The neuroimaging analyses revealed reduced neural activity in five cortical regions, including the PCC, which is part of the self-referential CmS, during tsunami-evacuation video watching in the combination group compared to the evacuation-only group. Furthermore, PCC activity was positively correlated with the increase in evacuation intent, suggesting its relevance to the processing of effective disaster communication. In addition to these findings, supplementary analyses of single-message videos demonstrated that mechanism-only (Tm) and evacuation-only (Te) content elicited partially overlapping but distinguishable neural patterns. The mechanism videos recruited LSPL, RSPL, PHG, and PCC, whereas the evacuation videos produced robust activation in the LLG, RLG, LSTG, RSTG, and PCC. Direct comparison between the two message types showed that the Mech \(>\) Evac contrast yielded stronger activation in parietal and inferior temporal regions, while the Evac \(>\) Mech contrast exhibited stronger activation in PCC and bilateral superior temporal regions.

Previous neuroimaging studies on persuasive communication, decision making, and memory have consistently highlighted the role of the PCC as part of the CmS involved in self-referential, value-based processing, and episodic memory ^25,26. For example, research on smoking Cessation demonstrated a greater engage of PCC in high-tailored smoking Cessation messages ²⁷. In line with these findings, the present study also found that PCC activation was positively correlated with increases in evacuation intent, suggesting that PCC activity may serve as a neural index of the educational effect in disaster communication.

However, the combination of disaster mechanism and evacuation information led to reduced PCC activation compared with evacuation-only messages. This diminished response implies that presenting both content types together may have diluted the self-referential processing supported by the PCC, thereby undermining the educational effect at the neural level. This contrasts with prior findings in health promotion, where hybrid messages enhanced perceived risk ¹¹. One plausible explanation for this disruption is that mechanism and evacuation messages place demands on partially different cognitive operations–conceptual spatial reasoning versus procedural action planning. When presented simultaneously, these heterogeneous information types may require parallel allocation of attentional and interpretive resources, thereby reducing the depth of self-referential processing normally associated with evacuation content. Importantly, this interpretation should not be understood as evidence of cognitive overload in a strict sense, but rather as a hypothesis consistent with longstanding findings in educational communication research, which note that mixing heterogeneous forms of information can sometimes diminish the effectiveness of each component ^28,29.

In addition to PCC, diminished neural responses were observed in regions such as the bilateral superior temporal gyrus (STG), right lingual gyrus (RLG), and inferior occipital gyrus (IOG). The STG is implicated in auditory comprehension ³⁰ and insight-based problem solving ³¹. One previous study found that the STG is sensitive to surprisal during story comprehension ³². The LG is related to visual processing ³³ and non-moral emotional arousal ³⁴. Similarly, the IOG is also correlated with emotion regulation ³⁵ and visual recognition ³⁶. Taken together, one possible interpretation is that the combined presentation may have overloaded or fragmented participants’ cognitive and emotional engagement, weakening the clarity or salience of evacuation-related cues. Like these results, additional fMRI results under the Evac \(>\) Mech comparison also showed greater activity in the PCC and bilateral STG, which align with theoretical accounts suggesting that understanding the need for evacuation involves evaluative decision-making processes supported by cortical midline structures as well as temporal–parietal regions involved in the social-contextual interpretation of risk. The presence of PCC and superior temporal activation during evacuation videos therefore reflects the cognitive demands of understanding evacuation necessity ^19,20,21.

The mechanism-only videos elicited activation in regions linked to spatial reasoning and geophysical understanding, including the SPL, PHG, and PCC, consistent with prior research showing that comprehension of natural-hazard mechanisms relies on medial temporal–parietal systems ^17,18. However, the ITG, as an unanticipated region, appeared in the results and retained activity in the Mech \(>\) Evac contrast, in contrast to the LSPL, PHG, and PCC, which lost activity. This could be because the stimulus material for this experiment was not fully controlled; thus, these results should be treated with caution.

From a practical perspective, the findings caution against the assumption that more information necessarily improves preparedness outcomes. While combining content types may seem beneficial, it may inadvertently attenuate the neural and psychological mechanisms that promote behavior change ^7,8. Disaster educators and communicators should consider message specificity and cognitive load when designing instructional materials, especially under time-constrained or emotionally charged scenarios.

Although the omnibus ANOVA indicated a significant overall group effect, the limited sample size substantially reduces statistical sensitivity, and only the contrast between the Evac and Cont groups reached significance under Tukey correction. The absence of significance for other comparisons—particularly the Mech and Comb groups—should therefore be interpreted as a possible consequence of insufficient power rather than evidence of no educational effect. Given these considerations, the behavioral findings should be treated with caution.

Regarding the neural results, it is important to clarify that behavioral measures index the educational effect, whereas the fMRI contrasts capture neural responses to different types of video content. A positive association between PCC activation and evacuation intention specifically in the conditions that contained evacuation-instruction content was observed, suggesting that PCC engagement may serve as a neural marker of educational processing. The Evac condition produced relatively stronger PCC responses, whereas the Comb condition showed weaker responses, even though both conditions contributed to the correlation pattern. This difference does not imply separate analyses or isolated mechanisms across subgroups. Instead, it indicates that variations in message composition may influence the degree of self-referential engagement during learning, which in turn relates to subsequent preparedness behavior. Also, this differentiation highlights the potential advantage of incorporating neuroimaging measures to evaluate the effectiveness of disaster education materials, especially when behavioral outcomes alone may not fully capture underlying cognitive processing differences ^37,38.

Nonetheless, several limitations should be noted. Most importantly, the final sample size after applying the attention-task exclusion criterion remains modest for a between-group behavioral and fMRI design. The reduced sample size inevitably limits statistical power and increases the risk of Type II errors. Consequently, the absence of significant differences between some conditions—particularly the Mech and Comb groups—should be interpreted with caution. Moreover, the small sample may restrict the generalizability and stability of both behavioral effects and neural activation patterns. The simulation nature of the decision-making task may also limit the generalizability of results to real-world evacuation behavior. Additionally, although our factorial design allows comparisons across message types, the number of mechanism and evacuation instruction videos shown in the Comb group differed from those of the other groups, which may have confounded interpretation. Furthermore, differences in video length, informational density, and visual complexity between each group may cause a stimulation intensity discrepancy, thus reflecting general processing demands rather than message-type effects alone. Control video content could also affect participants’ performance, as it contains information to be understood, thus covering up some cognitive activities in the results. In addition, choosing university students as participants has its limitations. While university students provided a methodologically advantageous sample for an fMRI-based educational experiment—given their generally high task compliance, stable attentional performance, and suitability for laboratory-based cognitive tasks ³⁹—their use also introduces limitations in terms of external validity. Young adults differ from coastal residents, older adults, disaster-experienced individuals, or tourists in risk perception, emotional reactivity, and real-world decision-making under stress. Although students in Sendai often visit nearby coastal destinations, which gives some contextual relevance to tsunami-related preparedness, this does not make them representative of populations who routinely live with tsunami risk. Therefore, the present study should be viewed as a controlled preliminary investigation of educational mechanisms. It is also worth mentioning that the present study cannot precisely determine how neural variations map onto levels of conscious intention, because fMRI activity was measured during video viewing rather than during the decision-making phase. Future studies should consider balancing video quantity and quality or using regression models that incorporate exposure duration or intensity as a covariate, and offering control videos that cost equivalent sensory resources but less cognitive demands, examining whether the observed behavioral and neural patterns extend to populations with different age ranges, disaster experiences, and geographic contexts.

5. Conclusion

This study explored how different types of tsunami educational videos influence both evacuation intention and neural processing. In the conditions that produced measurable increases in evacuation intention–namely those including evacuation-instruction content–activation in the posterior cingulate cortex (PCC) showed a positive association with behavioral improvement. This pattern aligns with findings from health-communication research, suggesting that PCC engagement may also serve as a neural marker of educational processing in the context of disaster-risk communication. Building on this observation, our results further suggest that combining mechanism explanations with evacuation instructions may reduce the educational effectiveness of evacuation-focused messages. In the combined condition, PCC engagement was weaker than in the evacuation-only condition, indicating that merging conceptually distinct information types may dilute self-referential processing that supports preparedness. Future research with larger samples is needed to confirm these possibilities and to inform the design of disaster-education materials that optimize both cognitive processing and behavioral outcomes.

Appendix A. Hazard Mechanism Videos

Table 3 shows the description, length, and the link of each video. Add “https://youtu.be/” before links to edited videos and sources. Videos without a source link mean we lost access to the original video from August 2025.