Gender is a socio-biological factor that interacts with genetic and hormonal and plays an important role in human psychosocial development [1-5]. As gender is considered an important factor that influences how people behave and interact in society, it is a critical socio-biological determinant among young people in the conceptualization of moral behaviour[6-9]. Thus, controlling the gender factor in the analysis has been strongly recommended to deal with the complexity of health issues [10-13].

Whether and how gender differences manifest in moral judgement has recently been the focus of much research in the field of moral psychology [14-18]. Moral psychologists such as Capraro and Sippel [19] hypothesized that gender differences in moral dilemmas are driven by emotional salience rather than a violation of the practical imperative. In this case, they believe that women should behave differently than men in these situations. Jaffee and Hyde [20] conducted a meta-analysis to quantitatively review the research on gender differences in moral orientation. Despite the relatively small difference between males and females, there were differences in care orientation favouring females and differences in justice orientation favouring males.

The bio-behavioural model suggests that males and females have different capacities for empathy. This argument can be seen in Christov-Moore et al.'s review work [21], which stated that the neurobiological underpinnings of empathy reveal significant quantitative gender differences in the basic networks involved in affective and cognitive forms of empathy.

Moral violation refers to behaviour that violates social norms and is frequently judged by society [22-26]. It highlights three main schools of thought that address the idea of moral judgement - Piaget’s moral cognitive development model, the social intuitionist model, and the dual-processing theory [27-33]. The dual-processing theory and the social intuitionist model place special emphasis on moral emotions in people, which are a subset of basic human emotions like rage and disgust and have an impact on moral judgement [27, 28, 34].

A neuroscience approach was implemented in this study to determine whether there is a neurological basis for the study of moral intuition. Recent electroencephalogram (EEG) studies have demonstrated that different types of moral violation can affect how one perceives moral violation, with significant differences in brain wave amplitude observed (22, 35-36). According to the findings of Zhang et al. [36], moral elicitors produced amplitudes that were larger than those produced by core disgust and neutral images, indicating that moral emotions are distinct from core emotions in a neuroscientific sense. In a similar vein, research in the field of neuro-cognition has identified P300 as a neuro biomarker that can be used to explain the psychophysiological mechanisms underlying behavioural issues [37].

At least two critical points should be highlighted as gaps in this area of study. First, the interpretation of ‘gender influence’ is lacking in the above-mentioned studies, especially the evidence from the neuroscientific data (i.e. electrophysiological data). The use of event-related potential (ERP), for example, offers evidence of the brain-wave pattern (associated with the small alterations in the electroencephalogram) recorded on the scalp that is timed to the commencement of an event such as a sensory stimulus or a motor act. Electroencephalography offers a medium to comprehend neurobiological dysregulation, with the potential to explore neurotransmission. Thus, this ERP method is an appropriate approach, as compared to other neuroscience methods, due to its ability to explain the human psycho-behavioural dimension from the brain potential parameter, such as the P300 component. Second, there has been no previous study specifically considering the neural-morality properties associated with the different contexts of immoral behaviour. Therefore, it is hypothesized that emotional attention to the different contexts of immoral behaviour (i.e., living beings and non-living beings) is influenced by the gender factor.

According to the results of the analysis of variance (ANOVA) for a two-way mixed design, which included gender as a between-subject effect and moral cognition P300 amplitude as a within-subject effect, there was a significant interaction between gender and electrical brain activity (as measured by P300 amplitude) in the frontoparietal area [F (2, 48) = 6.60; p0 .01]. Females revealed greater amplitude towards living beings and non-living beings stimuli than males, with an exemption to neutral stimuli. The interaction is depicted in Fig. (2). However, other brain regions did not show any interaction with gender, i.e., frontal [F (1.95, 46.79) = 2.98; ns], central [F (2, 48) = 0.47; ns], temporal [F (2, 48) = 1.40; ns], parietal [F (2, 48) = 0.38; ns] and occipital [F (2, 48) = 0.27; ns] (Table 1).

An effect size analysis was carried out for frontoparietal data to observe the difference in electrical brain activity (P300 amplitude) between males and females, specifically for each type of visual moral stimuli. It showed that Cohen’s-d is trivial for both living being and nonliving stimuli. Females exhibited greater amplitude means than males in both cases - Mean difference of 5.8 (SE 2.2) and 4.2 (SE 1.5), respectively. Meanwhile, in line with expectation, the effect size for neutral stimuli is small (Fig. 3).

Fig. (2). Interaction effect between gender and emotional cognition processing of visual moral stimuli.

Interestingly, behavioral data from participants' reactions to images of living beings (press button 1) and nonliving beings (press button 2) revealed a medium effect size between males and females, as reported by their reaction times in response to the stimuli (Fig. 4).

The difference in source localization between males and females in three conditions in response to living beings, non-living beings, and neutral images is depicted in Figures 5, 6 and 7. The living being category (Fig. 5) showed a clear distinction between males and females. The sagittal view revealed that males (A) showed more distributed activation than females (B). However, the intensity was one-fold higher in females (B) than in males (A). In terms of Broadman area, the values are considerably different, with females (B) being 11 and males (A) being 21.

Similar results were observed in the nonliving category (Fig. 6), in which neural activation was more widespread in males (A) than females (B). However, it was shown that females (B) displayed greater intensity than males (A). Another great difference was that both males (A) and females (A) differed greatly in the Broadman area.

Meanwhile, in the neutral image category (Fig. 7), even though the intensity was relatively different between males (A) and females (B), the Broadman areas between these two genders were almost similar.

Fig. (3). Differences in P300 amplitude across genders in the fronto-parietal region.

Fig. (4). Differences in behavioural response (reaction time) across genders.

Fig. (5). Source of moral cognition processing in males and females for immoral behaviour in living beings (sagittal view).

Fig. (6). Source of moral cognition processing in males and females for immoral behaviour in nonliving beings (sagittal view).

Fig. (7). Source of moral cognition processing in males and females for neutral stimuli (Sagittal view).

At least two important findings can be gleaned from this study. First, gender has had a significant impact on the processing of moral cognition, mainly in the frontoparietal area as indexed by P300 amplitude. The discovery of frontoparietal activation and its relationship to moral cognition processing requires the moral psychologist to pay close attention. Females showed significantly stronger moral cognition processing in the frontoparietal area, compared to males. Second, the frontoparietal region was more activated by living-being stimuli than non-living-being stimuli in both male and female genders.

Empirical research reported that females showed higher concern for a positive moral stream, such as care, fairness, and purity, in their moral judgments than males [39]. The discovery that females are less likely than males to respond in a utilitarian sense to moral dilemmas reflected females as more empathetic [40]. Utilitarianism is a moral philosophy that seeks to do the best for the greatest number of people while disregarding factors such as feelings and emotions, culture, and justice [41-43]. In a similar vein, Fumagalli et al. [44] reported that males provided significantly more useful responses to personal moral dilemmas, thus suggesting the difference between males and females in cognitive-emotional processes of personal dilemmas.

Evidence that females are more empathetic than males is becoming more widely accepted. In Derntl et al. [45], again, females were observed to rate themselves as more empathetic than males in the self-report questionnaires. Females demonstrated stronger neural activation in all empathy tasks in emotion-related regions, including the amygdala. Meanwhile, Rueckert et al. [46] found that females rated themselves as feeling happier and sadder than males, regardless of whether the event occurred to them, a friend, or an enemy. This suggests that differences in general emotional responsiveness may account for gender differences in empathetic responses.

We found that the frontoparietal brain area indicated greater activation when evoked by living being stimuli than nonliving being stimuli in both males and females. This discovery is significant because it adds to our understanding of earlier theories, such as the Moral Foundation Theory (MFT) - a thorough framework that looks at one's moral intuition and judgement [47-54]. As our data demonstrate, whether moral stimuli are living beings or nonliving beings, they have a significant impact on how people judge what is good and wrong. In other words, the capacity of moral stimuli might be what drives spontaneous action.

Neuro-cognition evidence in the neuroscience field has greatly contributed to explicating human morality [55-59]. We were not the first to realise the importance of the variation in moral stimuli that underlies moral cognition processing. According to a previous moral cognition model, different types of moral stimuli had distinct neurological foundations. For instance, Zhang et al. [36] discovered that core disgust stimuli had larger amplitudes of components N1, P2, and P3, whereas moral disgust stimuli had larger N2 amplitudes. Other than that, previous ERP research has shown that when subjects see someone else being hurt, different ERP components are involved. A longer electrocortical response lasting 200–300ms was seen over the centroparietal regions, which is followed by larger early ERPs over the frontocentral and frontal brain regions [60].

The discovery of the P300 neural component as a moral cognition marker, which we highlight in this study, has added to the existing literature. It is noted that the ERP modulations induced by emotional content are frequently characterized by increased activation of primary sites, including P300 [61]. Moral disgust stimuli, for example, increased P300 amplitude along with N200 and Late Positive Potential (LPP) amplitudes [36, 62]. Meanwhile, in multiple studies, the P300 component (as well as the P200 component) showed greater positive deflection in negative conditions than in neutral conditions. The P300, which frequently overlaps with LPP in earlier ERP studies, is frequently linked to attentional and memory processes [63-65].

The frontoparietal network has been recognised for its roles in human mental functioning, such as executive function and goal-oriented behaviour [66-69]. The role of the frontoparietal regions in abnormal emotional and cognition processing has also been highlighted in several scientific reports [70-73]. In the case of Social Anxiety Disorder (SAD), patients showed the ability to downregulate negative emotions using both reappraisal and acceptance and demonstrated effective recruitment of frontoparietal regulatory regions [74]. In different cases, the neural interface between negative emotion regulation and motivation for change in cocaine-addicted patients revealed emotional-related activation in the frontoparietal engaged during emotion regulation [75]. The important role of the frontoparietal as a set of regions involved in cognitive control of attention and emotion regulation was further highlighted by Kaiser et al. [76], who reported hypoconnectivity within the frontoparietal network in major depressive disorder. Major depressive disorder (MDD) has a connection with imbalanced communication among large-scale brain networks.

Nonetheless, this current discovery should consider the socio-demographic factors of the participants involved. Since they were university populations, this finding perhaps can not be generalized to a wider population. However, the novelty of the study, which looks specifically at the moral foundation of immoral behaviour (i.e., living and non-living beings of immoral behaviour), should be emphasized and highlighted as a research strength.

Gender and moral cognition interact primarily in the frontoparietal brain region. As indexed by the P300 amplitude, immoral behaviour toward living beings is associated with greater neural cognition processing in females than in males. This discovery contributes significantly to the field of moral psychology by improving the understanding of the moral foundation of neurophysiological evidence. This discovery contributes significantly to the field of moral psychology by providing a better understanding of moral foundations. This neuroscientific evidence could be an important referral for psychologists in mapping the gender-based patterns of moral empathy that link to brain function.

Nasir Yusoff conceptualized, designed, and prepared the initial draft and framework and interpreted the data. Chin Chun Ming and Mohd Faizal Mohd Zulkifly reviewed the measurement adaptation, supervised the findings of the study, made corrections in English, and reviewed the manuscript.

All authors discussed the results and contributed to the final manuscript.