Stanford Professor Baba Shiv has done some fascinating research on the role of neurostructures related to motivation, emotion, and decision making. Shiv argues that it's important to take the stress out of a situation if we want people to think creatively, engage in constructive dialogue and debate, and avoid becoming defensive. By taking the stress out of a situation, we can help others move into a "challenge" mindset rather than a "failure" mindset. In other words, we can encourage them to view a critique as "an exciting challenge rather than a failure." They become like the kid playing a videogame trying to conquer the next level of the game, rather than the person who recoils in the face of negative feedback.
Shiv explains, for instance, that you should take someone on a walk, preferably in the morning, when giving them feedback. Why? The key is serotonin, a neurochemical that helps put us in a calm state, as opposed to a stressful state of mind. Serotonin levels appear to be highest in the morning. Moreover, going on a walk outdoors helps to elevate levels of serotonin. Thus, this technique may help shift someone into a "challenge" mindset, which can make them less defensive about the feedback that you are going to provide.