Evolutionary psychology explains and predicts human behaviour based on its adaptive value. Some apparently non-adaptive behaviours such as humans’ devotion to music can be explained by sexual selection of costly signals, since it takes time and effort to learn to play an instrument well. Here, participants rated pictures of persons of the opposite sex that were said to play a piece of music that was heard while watching each picture. The music performances were either of low, medium, or high level of skill, and a better performance was predicted to lead to higher ratings of partner attractiveness because it is more costly. No effect of the music was found, except that women rated men as less desirable for a long-term relationships when the skill level was high than when it was medium. / Evolutionspsykologiska teorier förklarar och predicerar mänskligt beteende utifrån dess adaptiva värde. Vissa uppenbart icke-adaptiva beteenden, som människans hängivenhet till musik, kan förklaras som sexuell selektion av kostsamma signaler, eftersom det kräver tid och möda att lära sig bemästra ett instrument. Deltagare fick skatta bilder på personer av motsatt kön som påstods spela det musikstycke som hördes medan man tittade på varje bild. Musikutförandet var antingen av låg, medel, eller hög skicklighet, och ett bättre utförande förväntades ge högre skattningar av partnerattraktivitet eftersom det är mer kostsamt. Ingen effekt av musiken förelåg, förutom att kvinnorna skattade män som mindre attraktiva för ett längre förhållande när skicklighetsnivån var hög jämfört med när den var medelhög.

What do we do when we realise that others with whom we interact already know something about relevant qualities of ours? Do we relying on the information that we naturally emit to get our message across, or do we take actions to try to change the situation in our favour? And, does the information that we emit, generated intentionally or unintentionally, allow us to cooperate with others and conflict to be resolved peacefully? Drawing on signalling and 'countersignalling' theories, and a recent behavioural theory, I explore these questions using two experiments in which the relevant qualities are trustworthiness and toughness, and observational data from the 1997 Survey of Inmates in State and Federal Correctional Facilities concerning violence among prisoners. In the experiments, subjects, who do not know what will follow, initially create a natural indicator of their qualities, and subsequently, have the opportunity to send another indicator, this time fully informed. In one experiment, consistent with countersignalling theory, subjects whose generosity is clear deign to send further information, while those whose generosity can be called under question choose to update their initial action the most. In the other, the toughest subjects put the most effort into getting their message across. Consistent among both, senders' actions correspond to receivers' evaluations. Finally, I find that pertinent information can allow conflicts to be resolved successfully; it is linked with less violence in prison and in a laboratory-based contest.

This thesis attempts to provide both an explanatory model and to forecast settlements using large-n statistical analysis and machine learning. By asking the question of how costly signals affect the likelihood of conflict settlement, and drawing upon the literature on bargaining and signaling, it argues that when the challenging actor publicly state their demands and policy desires, they are sending costly signals, revealing information about their willingness to fight. This information is used by conflict parties to recalculate costs of war, causing them to eventually locate an agreement which both parties prefer continued fighting. As such, the mechanism suggests that a greater number of such signals means a greater chance at locating such an agreement, resulting in a greater chance of settlement. Additionally, connecting the signal to the issue at stake, I argue that territorial signals would be especially important, in part because they are often seen as indivisible, suggesting that signals relating to territory would be especially important relative to signals of comparable policy domains. The results are statistically significant in support of the first hypothesis but findno benefit to predictive performance from costly signals. In contracts territorial signals are neither statistically significant, nor contribute to predictive performance.

Peace communities are an “organized and sustained civilian mobilization in the midst of civil war to declare neutrality and to purposely end or prevent violent conflict in their community” (Kaplan. 2017). Scholars have long believed peace community could scale up from local oriented peace to connect to national peace processes but have overlooked the relationship between peace communities and their government. This study asks Why do governments respect the rules and boundaries of some peace communities and not others? I hypothesize that governments are more likely to respect peace communities with higher levels of cohesion, and more likely to disrespect less cohesive peace communities. I conduct a structured focused comparison study to test three empirical cases from the Philippines, comparing three first generation peace zones. I found some support for my hypothesis and causal mechanism. I then tested another empirical case from Colombia and found additional support for my hypothesis but not for my causal mechanism. Overall, this study presents a new theoretical framework, introduces a new dependent variable for measuring peace communities, and provids insight into the often under-researched first generation Philippine peace zones.