Foreheads for the most part indicate thinking style.
A straight forehead is someone who will think very much in lines. The best solution to any problem is the most rational and logical.
This is the forehead of the “warrior,” someone who comes into the world to see what’s wrong and fix it. As such when anyone is saying anything, their immediate thoughts are “what’s wrong with this?” and then “how can I fix it?”
To them they’re just helping, but to others it comes across as cynical and confrontational. They will not like it when someone says they have “hunch” or a “sense” of something. It’s too insubstantial for them.
Does this sound like you or someone you know?