Common goals play a profound influence in building trust. Part of this comes from interdependence. When we rely on each other we end up building trust. Now, there's something interesting that Tajfel found in the 1970s, where just even nominal groups. In these experiments, assigning people to a blue group or a red group and just calling them red or blue cause people to favor their group, trusting their group members more than they trusted out group members. Here's what's profound. If we do this with nominal groups, that is you've only been part of the red group for five minutes, it doesn't have any particular meaning, you can imagine what it means when we think about things in terms of a tribe, a religion, or a country. That is, the groups that we're in profoundly influence how we treat both the in group and the people outside of our group. Some great work that Taya Cohen has done looked at loyalty within groups and found the more loyal we are to our group members, the more we're accepting of warfare and violence against others. So something profound about how we think about and how we identify what is our group and what is somebody else's group. Now one thing that can influence how we think about our group membership are our common enemies. And when we have common goals they bind us together and there's nothing quite as profound as a common enemy in doing that. We saw after 9/11, Pakistan and the United States grow far closer. Countries that hadn't been well aligned before began to coordinate incredibly closely on security issues afterwards. And it's not just these two countries. You think about Russia and France, after attacks in the Middle East, how they changed their dynamics. And we see this in modern politics, but the same has been true for a long period of time in the past. So we saw for example the formation in the United States was profoundly influenced by the sense of group where initially in the French Indian War, the British were fighting against the French and the British use the colonist to fight against the French. This is the first on the colonist that actually acted together and in concert. And the British ended up training all the colonist including somebody named George Washington. And here George Washington actually fought against the French. The dynamics completely changed just a couple years later when it was in the American Revolutionary War, George Washington, again used the colonists as a collective, that group of colonists, they're fighting against the British. And who helped them? Well, the French jumped right in because the French were so eager to now fight the British. So we see these shifting sands of competition where we think about the groups and these shifting alliances between groups. And one of the profound ideas here is that common enemies can help us find super-ordinate goals. And these super-ordinate goals are what drives us together. So we can think about competing with some other outside competitor, some other outside enemy. Or if we think about something that we need to tackle together like solving a problem for our organization or solving an environmental issue together, those super-ordinate goals turn out to be incredibly important in helping us build trust. In summary, I want to think about the building blocks for trust. And so across this module, we thought about warmth and competence. We want to demonstrate high warmth and high competence but we also want to think about vulnerability. If we've demonstrated competence, vulnerability can help us demonstrate warmth. The communication process is very important, and we can have trust and institutions that can in some cases, substitute for trust in individuals. So for example, you might trust a contract we signed even if we don't trust the person as much. And reputations have helped us solve a lot of our key problems. We used to think about gossip as a tool for building reputations. But now, we think of online reputations being incredibly important. And then the common goals we have bond us together and help us build trust.