So a really predominant theory for understanding relationships, actually since the 1950s, has been George Homans' Social Exchange Theory. So basically this theory posits that human beings are rational creatures. We're only in relationships if the pros outweigh the cons. Essentially we do a cost benefit analysis and decide to ourselves. Does this relationship satisfy my needs? And I'm getting enough out of it? Or if I'm not getting enough out of it, then I'm leaving the relationship. So, Professor Tsang, does that theory really comprehensively explain relationships? >> Well, first of all, I have to say that like we probably still do not have a theory that comprehensively explains relationships.[LAUGH] Maybe not even SSLD. We're all trying to get different aspects of relationships better understood. But getting back to social exchange theory, I think you're right, like there are formulas that are using to help us understand what is happening. And you're right in pointing out that you're making the assumption that human beings are behaving rationally in a very logical, calculating manner. I just want to point out there are actually two formulas that are relevant here. The first one, obviously is weighing the cost benefit, like putting in so much and not getting enough. But very often when people get into relationship, they will also taking another angle to look at the so-called exchange. It's like how much have you put in and how much have I put in? Maybe I have put in not a lot and getting a lot out of that. But if I am sitting there looking at you and find that you are not putting in as much, the person may still feel dissatisfied because they're saying, oh that's not fair. So there are actually two sets of calculations that are supposedly going on. But as you have already pointed out, that has to assume that human beings are really rational. And I think we have all the reasons to believe that human beings actually aren't that rational. Interestingly, in year 2000, a Nobel Prize in economics was awarded to a psychologist or someone who did the experimental social psychology research. Daniel Kahneman put forward the Prospect Theory and that won him the Nobel Prize back in 2002. So what he actually is trying to point out, it's that like human beings actually rarely behave totally rationally. And he has decades of experimental findings to back up this claim. So this is also the same assumption made by a communist for a long time. That people they do things to maximize utility so they do those cost benefit analysis and make sure that I'm gaining the maximum possible out of any deal. But I think we now have a fair bit of evidence to show that like people do not really do that. So instead of looking at exchange, we may want to be understanding why people continue doing what they're doing. And then when we are in social services, for example, we find a lot of people sticking around in abusive relationships. Relationships that actually undermines their sense of self-worth. Relationships that are outright damaging, destructive, and people seem to stick around for a long time, right? So we really need to understand relationships beyond just looking at this like simple, rational exchange formula. And we have to be careful when we say that as well, because we do not want to give people this simple black, white, either, or. I'm not saying that the social exchange dimension is totally irrelevant. I'm saying that it may explain a certain percentage of variance. Some aspects of the relationship might be explainable with like social exchange formulation but relationships are obviously more complicated than that.