Use social media for any amount of time and eventually you will come across something that's designed to both appeal to the angels of your better nature and asking to make a (small) effort to support or propagate this appeal. The prime example of recent years is the ALS Ice Bucket Challenge.

When these charitable appeals take off, that's when social psychologist Sander van der Linden perks up. He studies 'viral altruism,' and in this Social Science Bites podcast he details to host David Edmonds how he studies this phenomenon.

"The idea," van der Linden says, "is that you can 'catch' altruism in a behavioral way. When someone acts altruistically online, you catch that behavior as a social contagion, which then causes you to adopt that behavior and encourage other people in your network to also engage in that behavior, which then spreads quickly and rapidly."

Van der Linden observes and describes the mechanics of these processes using something he calls SMArT, breaking down the online altruistic efforts by their social influence, moral imperative, affective reactions and translational impact.

This yardstick allows van der Linden to draw conclusions from what can be a smallish data set of unique events. SMArT allows van der Linden to find shared similarities that create body of data and which can be tracked. For example, van der Linden, is currently looking at the #MeToo movement to see if it fits into his scope of inquiry.

Van der Linden is a social psychologist and assistant professor in the Department of Psychology at the University of Cambridge where he directs the Cambridge Social Decision-Making Laboratory. He is also a Fellow in Psychological and Behavioural Sciences at Churchill College, Cambridge and an affiliated researcher at the Yale Program on Climate Change Communication at Yale University.