The awareness of casualties of war has been increasing within the global society nowadays. It leads to what Leidner et al. noted that, “globalization and cosmopolitanism have widened moral concern beyond group and state boundaries; … violence overall has declined steadily throughout human history” (p. 514). Nevertheless pessimistic view that human are violent “by nature” does exist and leads to understanding that violence and war are inevitable (p. 514). Leidner et al. suggest to perceive war and violence as a things that starting in the human mind and outcome of psychological mechanism in which dependent on people‟s perception, social experiences and the social conditions under which they interact (p. 514). Likewise Leidner et al. continue that, “’natural’ psychological mechanism are not necessarily immutable, but they can be adaptive to social, cultural, institutional influences; and these influences can determined whether and how our peaceful or warlike inclinations will manifest themselves in a given situation” (p. 514). These psychological reflections shown that psychology holds a very important role whether to perpetuate violent conflict or to facilitate intergroup reconciliation and positive relations.
Dynamic relation between groups that ended up on violent conflict needs to be examined and researched. In intergroup relations, it is differentiated between the so-called, ‘in-group’ and ‘out-group’ members who perceived to have different culture, belief system, traditions, and moral standards. This situation may lead into a positive image of the ‘in-group’ and, in the contrary, negative attitudes and behaviour toward the ‘out-group’ (p. 515). People seemingly identify themselves very tight to their own group (in-group). It is congruent to the topic about collective identity in Social Psychological Peace Research (SPPR). Since, the consequences of the group identification are the emersion of comparison and the consciousness of the ‘self’ and the ‘other’.
On the other hand, the ‘feeling of under attack’ as noted by Leidner, could easily drive a group to react strongly to the threat which frequently occurs from their fear of ‘out-group’ differences. As Leidner et al. underlined Bar-Tal‟s argument that stated “groups embroiled in conflict can develop a collective fear orientation and that this fear orientation promotes hostile bias toward the threatening outgroup that must be changed to achieve peace” (p. 517). The sparks of hatred and fear caused by the initiation of conflict might prolong conflict over time (p. 517). Double standard of morality is also likely employed to outgroup by consequences of moral concern for others is not absolute and violence against others become easily condoned and supported, then the willingness to help victims is reduced (p. 518). Therefore, in my viewpoint, promotion of nonviolent approach by psychological perspective on understanding, empathy and forgiveness toward the ‘out-group’ members as proposed by Leidner et al. is strongly needed in intergroup conflicts. Strong collective identity which sharply differentiate ‘in-group’ and ‘out-group’ members must be dismantled in globalization era in which more people interconnected each others. Therefore, the human minds that comprise of nonviolent and peace messages (peaceful mind) need to get more attention in promoting peace in the world today. 
Leidner, Bernhard et al., “Bringing Science to Bear-on Peace, Not War: Elaborating on Psychology‟s Potential to Promote Peace”, in American Psychologist October 2013, Vol. 6. No. 7, 514-526.