Why is it you still breathe when you're sleeping? I know, an odd question to ask. Well when I was younger, these kinds of questions popped up now and then. I've always been interested in why we do the things we do. Better yet, why do we do things without even thinking about it all the time.
The subconscious, also known as the unconscious mind as labelled by Freud, is pretty powerful. Its roots stem in part from our genes but mostly by our experiences as we were growing up. These experiences as we grow, determine how we see the world and our place in it. These preconceived ideas dictate how we react to situations and it happens faster than the blink of an eye. Some call it a knee-jerk reaction.
The unconscious, however, can be primed to react in certain ways. Take for example a study performed at Yale University where students were manipulated by a stranger prior to answering a question. On route to the study, students were bumped into by a laboratory assistant who was holding textbooks and a coffee. Some were holding a piping hot coffee, others were holding a cold iced coffee. The student was asked to hold the cup of coffee while the assistant picked up the books from the floor. Later in the study, the students were asked to describe a hypothetical person they simply read about. Interestingly enough, the students that held the iced coffee described the hypothetical person as being "colder, less social and more selfish" than the students that had momentarily held the hot cup of coffee.
The first thing you need to understand is your headshot isn't actually for you. It's for the viewer of it. So you need to create your headshot with the viewer in mind. Have you heard of the term "bitch face"? Have you ever walked down the street, a person walks past and You jump to the side and think, "whoa, she's not having a good day!" or, "Geez, I'd hate to bump into him in a dark alley!" These are all examples of your brain's unconscious kicking in and applying an emotion or feeling to what you are looking at. With headshots, we want to take advantage of that knee-jerk reaction but instead, evoke a specific reaction that positions you to your favour.
That reaction is a fine balance of emotions where you appear both confident and approachable at the same time. If you are too skewed towards confidence, they'll sense a bad attitude. If you are too skewed towards approachability, they'll sense inexperience. All without speaking or meeting you in person yet.
Before I go, do yourself a favour and take a look at your headshot. Show it to friends and family and ask them to describe the emotion they feel from it. Really get them to think about it, "it's a nice picture" isn't going to cut it. Ask them for honest emotion. A single word will do.
If you'd like to read more about the unconscious mind and how amazing it is, go check out this short article.