Managing relationships is a task that most people perform fairly adeptly. That’s not to say that we do so flawlessly—we certainly don’t—but we manage to avoid most major faux pas with regularity. Despite our ability to do so, many of us would not be able to provide compelling answers that help others understand why we do what we do.

Here’s a frequently referenced example: if you invited your friend over for dinner, many of you would likely find it rather strange—maybe even insulting—if after the meal your friend pulled out his wallet and asked how much he owed you for the food. Though we would find such behavior strange or rude, when asked to explain what is rude about it, most people would verbally stumble. It’s not that the exchange of money for food is strange; that part is really quite normal. We don’t expect to go into a restaurant, be served, eat, and then leave without paying. There are also other kinds of strange goods and services—such as and organs—that people often do see something wrong with exchanging resources for, at least so long as the exchange is explicit; despite that, we often have less of a problem with people giving such resources away.

This raises all sorts of interesting questions, such as why is it acceptable for people to give away things but not accept money for them? Why would it be unacceptable for a host to expect his guests to pay, or for the guests to offer?

The most straightforward answer is that the nature of these relationships is different: two friends have different expectations of each other than two strangers, for instance. While such an answer is true enough, it doesn't really deepen our understanding of the matter; it just seems to note the difference. One might go a bit further and begin to document some of the ways in which these relationships differ, but without a guiding functional analysis of why they differ, we would be stuck at the level of just noting differences. We could learn not only that business associates treat each other differently than friends (which we knew already), but also some of the ways they do. While documenting such things does have value, it would be nice to place such facts in a broader framework. On that note, I’d like to briefly consider one such descriptive answer to the matter of why these relationships differ before moving onto the latter point: the distinction between what has been labeled exchange relationships and communal relationships.

Exchange relationships are said to be those in which one party provides a good or service to the other in the hopes of receiving a comparable benefit in return; the giving thus creates the obligation for reciprocity. This is the typical consumer relationship that we have with businesses as customers: I give you money, you give me groceries. Communal relationships, by contrast, do not carry similar expectations; instead, these are relationships in which each party cares about the welfare of the other, for lack of a better word, intrinsically. This is more typically of, say, mother-daughter relationships, where the mother provisions her daughter not in the hopes of her daughter one day provisioning her, but rather because she earnestly wishes to deliver those benefits to her daughter. On the descriptive level, then, this difference between expectations of quid pro quo are supposed to differentiate the two types of relationships. Friends offering to pay for dinner are viewed as odd because they’re treating a communal relationship as one of exchange.

Many other social disasters might arise from treating one type of social relationship as if it were another. One of the most notable examples in this regard is the ongoing disputes over “nice guys," and the women with whom they hope to become intimate. To oversimplify the details substantially, many men will lament that women do not seem to be interested in guys who care about their well-being, but rather seek men who offer resources or treat them as less valuable. The men feel they are offering a communal relationship, but women opt for the exchange kind. Many women return the volley, suggesting instead that many of the “nice guys” are actually entitled creeps who think women are machines you put niceness coins into to get them to dispense sex. Now, it’s the men seeking the exchange relationships (i.e., “I give you dinner dates and you give me affection”), whereas the women are looking for the communal ones. But are these two types of relationships—exchange and communal—really that different? Are communal relationships, especially those between friends and couples, free of the quid-pro-quo style of reciprocity? There are good reasons to think that they are not quite different in kind, but rather different in respect to the details of the quids and quos.

To demonstrate this point, I would invite you to engage in a little thought experiment: imagine that your friend or your partner decided one day to behave as if you didn’t exist: they stopped returning your messages, they stopped caring about whether they saw you, they stopped coming to your aid when you needed them, and so on. Further, suppose this new-found cold and callous attitude wouldn’t change in the future. About how long would it take you to break off your relationship with them and move onto greener pastures? If your answer to that question was any amount of time whatsoever, then I think we have demonstrated that the quid-pro-quo style of exchange still holds in such relationships (and if you believe that no amount of that behavior on another’s part would ever change how much you care about that person, I congratulate you on the depths of your sunny and view of yourself as an altruist; it would also be great if you could prove it by buying me things I want for as long as you live while I ignore you).

The difference, then, is not so much whether there are expectations of exchanges in these relationships, but rather concerning the details of precisely what is being exchanged for what, the time frame in which those exchanges take place, and the explicitness of those exchanges. (As an aside, kin relationships can be free of expectations of reciprocity. This is because, owing to the genetic relatedness between the parties, helping them can be viewed—in the ultimate, fitness sense of the word—as helping yourself to some degree. The question is whether this distinction also holds for non-relatives.)

Taking those matters in order, what gets exchanged in communal relationships is, I think, something that many people would explicitly deny is getting exchanged: altruism for . That is to say that people are using behavior typical of communal relationships as an ingratiation device (Batson, 1993): if I am kind to you today, you will repay with [friendship/altruism/sex/etc.] at some point in the future; not necessarily immediately or at some dedicated point. These types of exchange, as one can imagine, might get a little messy to the extent that the parties are interested in exchanging different resources. Returning to our initial dinner example, if your guest offers to compensate you for dinner explicitly, it could mean that he considers the debt between you paid in full and, accordingly, is not interested in exchanging the resource you would prefer to receive (perhaps , complete with the possibility that he will be inclined to benefit you later if need be). In terms of the men and women example for before, men often attempt to exchange kindness for sex, but instead receive non-sexual friendship, which was not the intended goal. Many women, by contrast, feel that men should value the friendship…unless of course it’s their partner building friendship with another woman, in which case it’s clearly not just about friendship between them.

But why aren’t these exchanges explicit? It seems that one could, at least in principle, tell other people that you will invite them over for dinner if they will be your friend in much the same way that a bank might extend a loan to person and ask that it be repaid over time. If the implicit nature of these exchanges were removed, it seems that lots of people could be saved a lot of headache. The reason such exchanges cannot be made explicit, I think, has to do with the signal value of the exchange. Consider two possible friends: one of those friends tells you they will be your friend and support you so long as you don’t need too much help; the other tells you they will support you no matter what. Assuming both are telling the truth, the latter individual would make the better friend for you because they have a greater vested interest in your well-being: they will be less likely to abandon you in times of need, less likely to take better social deals elsewhere, less likely to betray you, and the like. In turn, that fact should incline you to help the latter more than the former individual. After all, it’s better for you to have your very-valuable allies alive and well-provisioned if you want them to be able to continue to help you to their fullest when you need it. The mere fact that you are valuable to them makes them valuable to you.

This leaves people trying to walk a fine line between making friendships valuable in the exchange-sense of the word (friendships need to return more than they cost, else they could not have been selected for), while maintaining the representation that they are not grounded in explicit exchanges publicly so as to make themselves appear to be better partners. In turn, this would create the need for people to distinguish between what we might call “true friends”—those who have your interests in mind—and “fair-weather friends”—those who will only behave as your friend so long as it’s convenient for them. In that last example we assumed both parties were telling the truth about how much they value you; in reality we can’t ever be so sure.

This strategic analysis of the problem leaves us with a better sense as for why friendship relationships are different from exchange ones: while both involve exchanges, the nature of the exchanges do not serve the same signaling function, and so their form ends up looking different. People will need to engage in proximately behaviors for which they don’t expect immediate or specific reciprocity in order to credibly signal their value as an ally. Without such credible signaling, I’d be left taking you at your word that you really have my interests at heart, and that system is way too open to manipulation.

Such considerations could help explain, in part, why people are opposed to exchanging things like selling organs or sex for money but have little problem with such things being given for free. In the case of organ sales, for instance, there are a number of concerns which might crop up in people’s minds, one of the most prominent being that it puts an explicit dollar sign on human life. While we clearly need to do so implicitly (else we could, in principle, be willing to exhaust all worldly resources trying to prevent just one person from dying today), to make such an exchange implicit turns the relationship into an exchange one, sending a message along the lines of, “your life is not worth all that much to me.” Conversely, selling an organ could send a similar message: “My own life isn’t worth that much to me.” Both statements could have the effect of making one look like a worse social asset even if, practically, all such relationships are fundamentally based in exchanges; even if such a policy would have an overall positive effect on a group’s welfare.

References: Batson, C. (1993). Communal and exchange relationships: What is the difference? & Social Psychology Bulletin, 19, 677-683.

DeScioli, P. & Kurzban, R. (2009). The alliance hypothesis for human friendship. PLoS ONE, 4(6): e5802. doi:10.1371/journal.pone.0005802