Updated: Nov 8, 2021
In 1960 an MIT professor, Douglas McGregor, published The Human Side of Enterprise. In his book, McGregor described two theories explaining how managers' beliefs about what motivates their people affect their leadership style.
Theory X - people dislike their work, avoid responsibility, have to be controlled and supervised to deliver work, are unmotivated and lazy, and lack ambition.
Theory Y - people like and want to work, take ownership of their work, want autonomy and independence, view work as fulfilling and challenging.
Your assumptions dictate how you lead people. How you lead people impacts how they perform. How they perform reaffirms your assumptions.
If you assume people are lazy, you won't give them responsibility. If you don't give them responsibility, they will become disengaged. If they become disengaged, they won't take initiative. If they don't take initiative, you will think they are lazy.
It's often said McGregor's book is misunderstood that theory X workers do not exist. That they have never existed and never will. That theory X is just an ugly prejudice about other people at work. It's easier to point fingers at others than it is focusing on our own shortcomings.
Either way you look at it, you have the power to break the cycle by leading better and believing the best in people.