While my father was very humorous and enjoyed telling jokes, he also had a side of him that used humor and sternness. He purchased a shaving strap from our barbershop to have in the house. He wrote on a piece of paper, psychology and scotch taped it to the strap. He announced to my sister and I that if we misbehaved he would, "use psychology on you."
Thus, at any point he felt the need to remind us that we needed to behave, he would pronounce, "I will use psychology on you." Jean and I immediately knew what that meant and without protestation changed our behavior. My father would evoke this saying, even with company around, or perhaps especially if company were around, since only my sister and I knew what that meant. To others hearing this it was a cute saying and comported to my father using his sense of humor, or so they thought, but we knew differently.
In fact it was rarely, if ever used, but nonetheless the statement was a code for what might happen to us if we didn't listen to him.
My father was extremely generous with his affections and to us he was a kind and wonderful man.
It is a testament to his humor and yet his profound assessment of how a child should be raised, seen but not heard, a throwback to his childhood rearing. However that might sound it was done with love.
So, if you are using psychology with people, and/or children, please remember that psychology shouldn’t hurt.