In professional or everyday settings, individuals frequently face moral choices that impact others’ well-being, such as prioritizing patients in an overcrowded emergency room or allocating scarce resources.

These decisions, especially in critical and emergency contexts, are inevitable and complex, requiring evaluations under uncertainty and emotional pressure. They involve balancing benefits and ethical conflicts (e.g., sacrificing one for many), relying not only on objective evaluations but also on applying fundamental moral principles like distributive justice, fairness, merit, and utilitarianism. These principles are influenced by the external context and emotional involvement (O’Fallon and Butterfield, 2005; Kish-Gephart et al., 2010). In this sense, moral judgment can be defined as the process of evaluating the ethical acceptability of a behavior or a series of behaviors (Reidenbach and Robin, 1988). Recent affective neuroscience research highlights that these choices unfold within dynamic social interactions, where non-verbal emotional cues (such as facial expressions, gaze, body posture, and vocal tone) act as communicative channels that convey empathy, agreement, or tension (Kret and de Gelder, 2012; de Gelder, 2009). Recognizing these embodied components is important for achieving ecological validity when studying moral behavior.

Neuroscience and cognitive psychology have adopted experimental methodologies aimed at analysing the mechanisms underlying moral judgment. Among these, the use of hypothetical moral dilemmas has proven particularly useful, as they allow for isolating and examining the cognitive and emotional processes involved in moral decision-making, in the absence of real-world consequences (Sinnott-Armstrong, 1987; Tasso et al., 2017; Palmiotti et al., 2020).

Moral judgment is thought to arise from a conflict between utilitarian and deontological perspectives: the former maximising collective well-being even when this is achieved through inequality, the latter adhering to moral norms regardless of outcomes (Greene et al., 2004, 2008). According to the dual-process model of moral cognition, utilitarian choices depend on cognitive control, whereas deontological ones are emotionally driven (Greene et al., 2001; Haidt, 2001). Thus, within this framework, emotions cannot be considered peripheral events but play a central role, acting as communicative and motivational forces, dynamically influencing attention, empathy, and judgment through expressive and physiological dimensions.

To further explore the neural substrates underlying these cognitive and emotional mechanisms, neuroimaging studies have examined which brain regions are engaged during moral decision-making, such as the dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), and anterior insula during moral decision-making; with the ACC particularly involved in emotionally complex dilemmas (Greene, 2007; Hutcherson et al., 2015).

However, these are limited in capturing the dynamic and reciprocal nature of real-time social interactions.

To address this limitation and to investigate the neurocognitive dynamics underlying real-time interpersonal interactions involving joint moral evaluation, recent research employs the use of hyperscanning to record simultaneous brain activity from multiple participants. In particular, functional near-infrared spectroscopy (fNIRS) has been largely used because it allows the analysis of hemodynamic signals resulting from prefrontal cortex (PFC) activation, being comparable with BOLD signals obtained by fMRI (Sato et al., 2013); allowing for the explanation of neuronal activation in terms of an increase in oxygenated haemoglobin (O₂Hb) and a concomitant decrease in deoxygenated haemoglobin (HHb). This is indicative of an increase in local metabolic activity. Conversely, the opposite pattern has been interpreted as indicative of neural inhibition or reduced activation in specific cortical areas. In particular, the HHb component has been linked to inhibitory processes, as its increase is frequently regarded as a potential indicator of functional suppression, especially during the execution of cognitively demanding tasks (Cui et al., 2010; Hoshi, 2016; Balconi and Vanutelli, 2017a; Acconito et al., 2025).

More specifically, Dashtestani et al. (2018) employed fNIRS to investigate the brain’s hemodynamic activity during moral decision-making, finding that impersonal (cognitive) moral dilemmas elicited greater O₂Hb changes in PFC, particularly in the left DLPFC, compared to personal (emotional) dilemmas. This effect was especially noticeable during non-utilitarian responses, suggesting a critical interplay between emotional and rational processing in moral judgment and validating fNIRS utility for exploring hemodynamic correlates in individual contexts. Recognizing that moral decisions are often social, the integration of fNIRS during hyperscanning offers a promising development for future research to study real-time, shared moral evaluation (Balconi and Vanutelli, 2017a; Quaresima and Ferrari, 2019; Acconito et al., 2025).

To address the lack of research on joint ethical evaluation, the concept of negotiated moral decision-making was introduced. This process requires two or more individuals to confront each other to reach an agreement on a morally relevant choice. It entails integrating diverse perspectives, balancing personal versus collective beliefs, and adopting an ethically defensible solution, and the need for advanced skills such as empathy, theory of mind, emotional regulation, and acceptance of compromise (Decety and Cowell, 2014). Its complexity stems from the fact that participants must confront deeply personal values often perceived as non-negotiable, which resonate with their own moral identity. Also, reciprocal affective responses can play a pivotal role, influencing moral evaluation, also through the manifestation of subtle interpersonal cues, such as facial expression, voice tone, gaze, and body posture. These spontaneous signals, in fact, could reflect how emotions are conveyed, perceived, and managed during shared moral evaluation. Thus, these dynamics have the potential to induce cognitive and emotional tensions, which can limit the establishment of a shared agreement, particularly in the absence of explicit normative references or collectively recognized objective criteria.

The investigation of negotiated moral decisions can be facilitated by the utilization of structured dyadic dilemmas, such as those concerning the allocation of life-saving care under conditions of limited resources (Persad et al., 2009; Balconi and Fronda, 2020). In such contexts, decisions must be made collectively, despite the absence of a clearly defined normative hierarchy. This process involves the deliberate exclusion of at least one ethically valid option and necessitates the reassessment of one’s moral positions, frequently influenced by anticipatory emotions such as guilt and fear of negative relational consequences (Gangemi et al., 2025).

In the present study, participants, organized in pairs, are asked to imagine themselves in the position of a physician forced to choose which of two patients to prioritize in treatment in a hypothetical pandemic emergency scenario. They negotiate a shared, ethically defensible solution, enabling the exploration of decision-making and neural dynamics of moral negotiation. Also, this approach thus allows the exploration of interbrain dynamics underlying affective attunement that often manifests through non-verbal cues. Recent literature distinguishes between social, affective, and informative gestures, each fulfilling distinct communicative functions such as initiating, maintaining, or interrupting interaction, expressing emotional states, or directing attention (Bavelas et al., 1992; Tomasello et al., 2005; Enfield et al., 2007; Kendon, 2017), contributing to the perception of inclusion, empathy, and cooperation (Balconi and Vanutelli, 2017b).

In line with the specific features of the proposed task, it is hypothesized that when participants are not aligned, either emotionally or cognitively, higher dissimilarity in the relevant brain areas will be observed, consistent with their neurofunctional properties. These patterns, modulated by the nature of the misalignment between partners, could represent dynamic indicators of the difficulty of achieving a shared moral agreement.

Specifically, cognitive misalignment between dyad members, such as differences in reasoning processes, normative interpretation, or analytical evaluation of the proposed situation, is expected to result in increased hemodynamic dissimilarity in the left prefrontal areas, which are traditionally associated with cognitive control and deliberative thinking. Conversely, when misalignment is emotional or affective (for example, due to differences in the intensity or quality of empathic responses), an increase in dissimilarity is expected in the activity of the right prefrontal areas, which are associated with emotional regulation and social cognition.

For HHb, the analysis with Channel only revealed a significant main effect [F_(3.21,45) = 3.20, p = 0.029, η²p = 0.186]. Post hoc comparisons (Bonferroni-corrected) revealed that EuDist (dissimilarity) was significantly higher for Channel 6 compared to Channel 3 (p = 0.022) (Figure 3).

No other significant results were found. No significant results were found for O₂Hb (all p > 0.50).

As regards behavioral data, all but one of the pairs reached a final agreement by selecting at least one of the options initially suggested by the individual members. Only one pair found a “third way” to reach an agreement. On average, it took 2.30 min to reach an agreement. In terms of the content of the agreements, seven of the fourteen pairs opted for emotionally oriented justifications, while the remaining seven chose cognitively oriented justifications.

The present study provides novel insights into the neurocognitive dynamics underlying negotiated moral decision-making in a realistic scenario inspired by the SARS-CoV-2 pandemic. Participants were presented with a realistic moral dilemma, requiring them to decide which of two elderly patients to prioritize in the event of resource constraints. This scenario gave rise to a conflict between competing moral principles, requiring integration of individual moral judgment with interpersonal coordination, approximating real-world shared decision-making (Decety and Cowell, 2014; Gangemi et al., 2025).

Although the DRI did not yield significant differences between aligned and misaligned dyads, this non-significant result is conceptually informative and suggests that neural dissimilarity occurs independently of the dyad’s reasoning alignment. Rather than being driven by specific dyadic reasoning styles, the observed pattern appears to reflect a more general feature of joint moral negotiation. In other words, the inter-hemispheric dissimilarity could reflect a general pattern of cognitive-emotional processing during joint moral negotiation, rather than being driven by specific dyadic styles.

On the other hand, the primary significant result shows a significant increase in dissimilarity in hemodynamic HHb activity between channel 6 (F6-F4, right hemisphere) and channel 3 (F5-F3, left hemisphere). In contrast, no significant differences emerged for O₂Hb.

This inter-hemispheric dissimilarity likely reflects complementary engagement of analytical reasoning (left PFC) and socio-emotional processing (right PFC) (Greene et al., 2004; Killgore and Yurgelun-Todd, 2007; Decety and Cowell, 2014; Patil et al., 2021). Conflict between these systems may reflect the effort to reconcile rational evaluations (e.g., establishing a clinical priority) with empathic concern (e.g., significant family ties), a dynamic intensified by interpersonal interaction (Dashtestani et al., 2018; Balconi et al., 2025).

The lack of clear normative criteria likely accentuated the tension between rapid, intuitive emotional responses and controlled, deliberate reasoning (Greene et al., 2001; Haidt, 2001), possibly leading to differences in neural activation patterns(Cui et al., 2012). The hemispheric asymmetry may further index a functional conflict between utilitarian logic and deontological norms, as participants justified their own stance while negotiating with others (Treviño et al., 2006; Balconi and Fronda, 2020). From an affective neuroscience perspective, such hemispheric differentiation may be consistent with differential involvement of prefrontal regions in processes related to the regulation of emotional contagion and empathic resonance, whereby the right PFC has been suggested to play a role in modulating the perception and expression of others’ emotions during interactive moral evaluation. However, even if these processes may involve emotional regulation and empathic engagement, the results of this exploratory study do not allow for precise attribution to specific regulatory mechanisms.

Finally, the role of the proposed scenario should be considered: the emotionally charged pandemic framing likely intensified affective engagement, consistent with evidence that framing influences moral judgment and bias under uncertainty (Tversky and Kahneman, 1981; Navarick and Moreno, 2022; Gangemi et al., 2025).

Furthermore, the dissociation between the HHb and the O₂Hb can be explained by their physiological differences. Generally, an increase in neuronal activity is associated with an increase in O₂Hb as a result of increased oxygenated blood flow, accompanied by a decrease in HHb due to increased oxygen extraction by tissues. However, these signals are not always symmetrical and can be differentially influenced by systemic factors and artefacts. Indeed, the HHb component is often considered to be relatively more stable and less susceptible to physiological interference or motion artefacts, especially in complex protocols such as hyperscanning. This makes it easier to detect functional differences between the brain regions involved and may reflect local metabolic changes associated with neuronal activity more directly than O₂Hb (Sato et al., 2013).

Taken together, these neurophysiological findings can be better understood if considering the embodied and interactive context in which moral negotiation occurs. In fact, although the present study aims to investigate the neurophysiological correlates of shared moral decision-making by examining the cognitive and emotional components of dynamic interaction rather than overt behavioral expressivity, acknowledging embodied dynamics provides an important conceptual background for interpreting interpersonal neural synchronization in realistic social contexts. The theoretical perspective offered by gesture and embodiment studies offers a valuable interpretive lens for understanding the interpersonal dynamics captured through hyperscanning, as the dialogic nature of the task likely involved the mutual perception and interpretation of subtle emotional cues (such as facial micro-expressions, tone of voice, and posture) that regulate interpersonal contact, convey affective information, and guide attention (Tomasello et al., 2005). In moral negotiation, such implicit expressive signals may represent the behavioral counterpart of the observed neural synchronization, accompanying verbal reasoning and emotional exchange while modulating empathy, inclusion, and cooperation (Balconi and Vanutelli, 2017b). Recognizing their potential involvement enhances the ecological validity of the neural findings and supports a socially grounded understanding of moral decision-making as a socio-emotional process.

Despite promising results, this study should be considered as preliminary due to the small sample size, and some limitations should be noted. Firstly, beyond visual inspection and exclusion of noisy channels, no automated motion correction algorithms were applied, and the optode configuration did not include short-separation channels. Although motion artefacts were minimized at the experimental level through task design and participant instructions, residual non-neuronal contributions to both O₂Hb and HHb signals cannot be entirely excluded. Thus, the observed effects should be interpreted as relative patterns of inter-hemispheric divergence, rather than as direct indicators of specific neural mechanisms. Secondly, despite the present task incorporating a realistic moral dilemma and facilitating face-to-face negotiation, it remains a hypothetical scenario with a limited duration (180 s). Consequently, while the design is more interactive and naturalistic than standard isolated paradigms, such findings should not be generalized to real-world clinical decision-making. Thirdly, the complexity of the evaluation task makes it challenging to accurately identify the specific factors contributing to neural synchronization or dissimilarity, such as empathy, emotional engagement, and communication strategies. Future studies could integrate behavioral measures (e.g., detailed coding of negotiation strategies, turn-taking, and non-verbal cues)individual profiles (e.g., empathy and moral traits), and dialogical content analysis, including non-verbal cues, to better understand sources of disagreement and compromise strategies. Additionally, another research perspective could be to integrate tools for detecting autonomic indices, such as skin conductance or heart rate variability, to capture physiological components related to motivational activation and stress. Combining cortical neurophysiological data with peripheral autonomic signals would allow distinctions to be drawn between cognitive and emotional processes, thereby contributing to a deeper understanding of the moral negotiation dynamic.

In conclusion, this preliminary study contributes to new insights into the understanding of moral judgment in interactive contexts, suggesting that moral negotiation is not simply the sum of individual evaluations; rather, it is a dynamic process involving the integration (and often conflict) of cognitive and emotional processes across both cerebral hemispheres, as well as the neural dynamics of shared morality. This opens up new perspectives for analysing cooperation, disagreement, and the construction of moral meaning in interpersonal relationships.