Psychology has identified many examples of cognitive biases and errors. In relation to gender, there are alpha bias (magnifying gender differences) and beta bias (minimising gender differences). In this chapter we identify another gender bias, gamma bias, which simultaneously magnifies and minimises gender differences. An example is domestic violence, where violence against men tends to be overlooked whereas violence against women is often highlighted. It is argued in this chapter that although we live in times where we now rightly talk a lot about conscious and unconscious bias against women, we are not yet conscious of our biases against men. The gender distortion matrix is proposed as a framework for identifying cognitive bias regarding men and boys.