Answer:
positive reinforcement
Explanation:
Positive reinforcement is a psychological behavior. It may be defined as the giving or providing someone with a rewards or a praising somebody when the person performed the desired action or work.
In the context, Preston John believes in the positive reinforcing his employees and personally mailing them and congratulating them for their hard work and achievements. He believes that by doing so, it will increase the likelihood of the good work performance of the employees in the future.