Humans have a habit of inserting themselves in the disputes of other people. We often care deeply about matters concerning what other people do to each other and, occasionally, will even involve ourselves in disputes that previously had nothing to do with us; at least not directly. Though there are many examples of this kind of behavior, one of the most recent concerned the fatal shooting of a teen in Ferguson, Missouri, by a police officer. People from all over the country and, in some cases, other countries, were quick to weigh in on the issue, noting who they thought was wrong, what they think happened, and what punishment, if any, should be doled out. Phenomena like that one are so commonplace in human interactions it’s likely the case that the strangeness of the behavior often goes almost entirely unappreciated. What makes the behavior strange? Well, the fact that intervention in other people’s affairs and attempts to control their behavior or inflict costs on them for what they did tends to be costly. As it turns out, people aren’t exactly keen on having their behavior controlled by others and will, in many cases, aggressively resist those attempts.

Not unlike the free-spirited house cat

Let’s say, for instance, that you have a keen interest in killing someone. One day, you decide to translate that interest into action, attacking your target with a knife. If I were to attempt and intervene in that little dispute to try and help your target, there’s a very real possibility that some portion of your aggression might become directed at me instead. It seems as if I would be altogether safer if I minded my own business and let you get on with yours. In order for there to be selection for any psychological mechanisms that predispose me to become involved in other people’s disputes, then, there need to be some fitness benefits that outweigh the potential costs I might suffer. Alternatively, there might also be costs to me for not becoming involved. If the costs to non-involvement are greater than the costs of involvement, then there can also be selection for my side-taking mechanisms even if they are costly. So what might some of those benefits or costs be?

One obvious candidate is mutual self-interest. Though that term could cover a broad swath of meanings, I intend it in the proximate sense of the word at the moment. If you and I both desire that outcome X occurs, and someone else is going to prevent that outcome if either of us attempt to achieve it, then it would be in our interests to join forces – at least temporarily – to remove the obstacle in both of our paths. Translating this into a concrete example, you and I might be faced by an enemy who wishes to kill both of us, so by working together to kill him first, we can both achieve an end we desire. In another, less direct case, if my friend became involved in a bar fight, it would be in my best interests to avoid seeing my friend harmed, as an injured (or dead) friend is less effective at providing me benefits than a healthy one. In such cases, I might preferentially side with my friend so as to avoid seeing costs inflicted on him. In both cases, both the other party and I share a vested interest in the same outcome obtaining (in this case, the removal of a mutual threat).

Related to that last example is another candidate explanation: kin selection. As it is adaptive for copies of my genes to reproduce themselves regardless of which bodies they happen to be located in, assisting genetic relatives in disputes could similarly prove to be useful. A partially-overlapping set of genetic interests, then, could (and likely does) account for a certain degree of side-taking behavior, just as overlapping proximate interests might. By helping my kin, we are achieving a mutually-beneficial (ultimate-level) goal: the propagation of common genes.

A third possible explanation could also be grounded in reciprocal altruism, or long-term alliances. If I take your side today to help you achieve our goals, this might prove beneficial in the long term to the extent that it encourages you to take my side in the future. This explanation would work even in the absence of overlapping proximate or genetic interests: maybe I want to build my house where others would prefer I did not and maybe you want to get warning labels attached to ketchup bottles.You don’t really care about my problem and I don’t really care about yours, but so long as you’re willing to help me scratch my back on my problem, I might also be willing to help you scratch yours.

Also not unlike the free-spirited house cat

There is, however, another prominent reason we might take the side of another individual in a dispute: moral concerns. That is, people could take sides on the basis of whether they perceive someone did something “wrong”. This strategy, then, relies on using people’s behavior to take sides. In that domain, locating the benefits to involvement or the costs to non-involvement becomes a little trickier. Using behavior to pick sides can carry some costs: you will occasionally side against your interests, friends, and family by doing so (to the extent that those groups behave in immoral ways towards others). Nevertheless, the relative upsides to involvement in disputes on the basis of morality need to exist in some form for the mechanisms generating that behavior to have been selected for. As moral psychology likely serves the function of picking sides in disputes, we could consider how well the previous explanations for side taking fare for explaining moral side taking.

We can rule out the kin selection hypothesis immediately as explaining the relative benefits to moral side taking, as taking someone’s side in a dispute will not increase your genetic relatedness to them. Further, a mechanism that took sides on the basis of kinship should be primarily using genetic relatedness as an input for side-taking behavior; a mechanism that uses moral perceptions should be relatively insensitive to kinship cues. Relatedness is out.

A mutualistic account of morality could certainly explain some of the variance we see in moral side-taking. If both you and I want to see a cost inflicted on an individual or group of people because their existence presents us with costs, then we might side against people who engage in behaviors that benefit them, representing such behavior as immoral. This type of argument has been leveraged to understand why people often oppose recreational drug use: the opposition might help people with long-term sexual strategies inflict costs on the more promiscuous members of a population. The complication that mutualism runs into, though, is that certain behaviors might be evaluated inconsistently in that respect. As an example, murder might be in my interests when in the service of removing my enemies or the enemies of my allies; however, murder is not in my interests when used against me or my allies. If you side against those who murder people, you might also end up siding against people who share your interests and murder people (who might, in fact, further your interests by murdering others who oppose them).

While one could make the argument that we also don’t want to be murdered ourselves – accounting for some or all of that moral representation  of murder as wrong – something about that line doesn’t sit right with me: it seems to conceive of the mutual interest in an overly broad manner. Here’s an example of what I mean: let’s say that I don’t want to be murdered and you don’t want to be murdered. In some sense, we share an interest in common when it comes to preventing murder; it’s an outcome we both want to avoid. So let’s say one day I see you being attacked by someone who intends to murder to you. If I were to come to your aid and prevent you from being killed, I have not necessarily achieved my goal (“I don’t want to be murdered”); I’ve just helped you achieve yours (“You don’t want to be murdered”). To use an even simpler example, if both you and I are hungry, we both share an interest in obtaining food; that doesn’t mean that my helping you get food is filling my interests or my stomach. Thus, the interest in the above example is not necessarily a mutual one. As I noted previously, in the case of friends or kin it can be a mutual interest; it just doesn’t seem to be the case when thinking about the behavior per se. My preventing your murder is only useful (in the fitness sense of the word) to the extent that doing so helps me in some way in the future.

Another account of morality which differs from the above positions posits that side-taking on the basis of behavior could help reduce the costs of becoming involved in the disputes of others. Specifically, if all (or at least a sizable majority of) third parties took the same side in a dispute, one side would back down without the need for fights to be escalated to determine the winner (as more evenly-matched fights might require increased fighting costs to determine a winner, whereas lopsided ones often do not). This is something of a cost-reduction model. While the idea that morality functions as a coordination device – the same way, say, a traffic light does – raises an interesting possibility, it too comes with a number of complications. Chief among those complications is that coordination need not require a focus on the behavior of the disputants. In much the same way that the color of a traffic light bears no intrinsic relationship to driving behavior but is publicly observable, so too might coordination in the moral domain need not bear any resemblance to the behavior of the disputants. Third parties could, for instance, coordinate around the flip of a coin, rather than the behavior of the disputants. If anything, coin flips might be better tools than disputant’s behavior as, unlike behavior, the outcome of coin flips are easily observable. Most immoral behavior is notably not publicly observable, making coordination around it something of a hassle.

 And also making trials a thing…

What about the alliance-building idea? At first blush, taking sides on the basis of behavior seems like a much different type of strategy than siding on the basis of existing friendships. With some deeper consideration, though, I think there’s a lot of merit to the idea. Might behavior work as a cue for who would make a good alliance partner for you? After all, friendships have to start somewhere, and someone who was just stolen from might have a sudden need for partial partners that you might fill by punishing the perpetrator. Need provides a catalyst for new relationships to form. On the reverse end, that friend of yours who happens to be killing other people is probably going to end up racking up more than a few enemies: both the ones he directly impacted and the new ones who are trying to help his victims. If these enemies take a keen interest in harming him, he’s a riskier investment as costs are likely coming his way. The friendship itself might even become a liability to the extent that the people he put off are interested in harming you because you’re helping him, even if your help is unrelated to his acts. At such a point, his behavior might be a good indication that his value as a friend has gone down and, accordingly, it might be time to dump your friend from your life to avoid those association costs; it might even pay to jump on the punishing bandwagon. Even though you’re seeking partial relationships, you need impartial moral mechanisms to manage that task effectively.

This could explain why strangers become involved in disputes (they’re trying to build friendships and taking advantage of a temporary state of need to do so) and why side-taking on the basis of behavior rather than identity is useful at times (your friends might generate more hassle than they’re worth due to their behavior, especially since all the people they’re harming look like good social investments to others). It’s certainly an idea that deserves more thought.