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Cambridge Social Decision-Making Lab

Department of Psychology

TEDx Cambridge2


What makes some social causes go viral but not others? Online social media platforms now offer the ability to connect and mobilize millions of people to action on important societal issues. In our latest research, published in Nature Human Behaviour, we evaluate how people engage with a number of popular social causes, such as the ALS Ice Bucket Challenge, which achieved unprecedented virality during the summer of 2014.

We analyzed the impact of the Ice Bucket Challenge by tracking common public interest indicators over time (e.g., google search terms, Wikipedia hits, financial donations). In doing so, we uncovered an important and intriguing pattern: once a cause has generated enough social momentum to go "viral", it reaches a social "tipping point" after which, public interest dissipates quickly and public engagement tends to revert back to pre-campaign levels. We refer to this pattern as the short "half-life" of viral altruism.

Part of the explanation is rooted in the psychology of "consensus", which tends to create a self-sustaining mechanism (i.e., if a video or meme has been viewed or shared let's say a million times, its popularity serves as social proof in itself that the content warrants attention). A consequence of this is that such social phenomena tend to elicit fairly superficial engagement from people, driven primarily by "extrinsic" rather than "intrinsic" (self-determined) motivations. This is consistent with behavioral trends we observed in prior work published in Nature Climate Change. In short, viral phenomena spread fast, but often fail to take root and sustain public attention and engagement in the long-term, captured nicely by the phrase; "a flame that burns twice as bright, burns half as long".

We then look at some of the common psychological characteristics of successful viral campaigns and summarize these with the acronym "SMART", which stands for; Social Influence, Moral Imperative, Affective Reactions and Translational Impact:



 Figure 1: The S.M.A.R.T Criteria for Viral Altruism

So-called "SMART" social causes are those that able to leverage social norms through peer-to-peer influence (e.g., the ALS Ice Bucket Challenge), establish a clear moral imperative for people to act (e.g., genocide, social injustice), elicit strong positive emotions (e.g., empathy) and are able to translate online "clicks" into sustained long-term engagement over time. Many social causes that have generated success and virality follow some of the S.M.A.R.T criteria, but ultimately fail to sustain long-term support. For example, the ALS Ice Bucket Challenge was re-launched in 2015 without much success. Other social issues, such as climate change, score very low across the SMART dimensions. Indeed, social norms around acting on climate change are not very well pronounced, most people do not view climate change as a moral issue and climate change is often seen as a psychologically abstract and distant issue.

The work was covered by the Times and Scientific American Mind. In a recent episode of Sage social science bites, Dr. van der Linden is interviewed about the work in detail. He also gave a TEDx talk about the topic (video below).

Viral Altruism: How to Spread Human Kindness