In 2004, Paul Zak and his research team ran three studies.

In the first, Paul and his team looked to see what occurred within the human body as individuals came to trust one another. By measuring different hormone levels in the body while individuals partook in scenarios designed to form and solidify connections, the team found that oxytocin increased as trust grew.

Then, Paul wondered what individuals could do to impact one another’s oxytocin levels. So in the second study, his team split experiment participants into two groups, who were both shown a video of a father playing with his child. That was all one group saw, but the other saw the father get closer to the camera and reveal that his son was dying of cancer.

Both groups had their oxytocin levels measured before and after watching the video. Paul and his team found that the second group, who had received the extra piece of information, had increases in their oxytocin levels. In other words, they had come to trust the man because he had revealed the emotional information.

In the third study, Paul questioned whether gaining trust through communication could cause behaviour change. Twenty people from a group of forty were injected with oxytocin so that they would immediately trust other individuals. The research team gave all forty £5 and asked them to watch a series of public service announcements from United Kingdom charities.

Afterwards, the team asked all forty individuals whether they’d like to donate their £5 to one of the charities. The individuals injected with oxytocin were 56% more likely to.

Paul has continued to work in this field, seeing how the building of trust leads people to do things that are costly to them in terms of time or money.