Any qualified acting coach or teacher will tell you that you need thought. Thought is what motivates us to physical and verbal action.
What acting teachers and coaches often leave out is that a thought that is not connected to a strong enough idea or opinion will never register on your face. Think about it, you have many thoughts every day, most are not strong enough to change the appearance of your face, which is what others around you pick up. It's what the camera picks up. Even if you have a thought strong enough there is still no guarantee the camera will capture these thoughts based on things I’ve already talked about in earlier posts, such as, how you are wired to express (introverts vs. extroverts), display rules, etc.
What I tell my actors is this:
Thought not connected to a strong enough idea or opinion will often leave the face blank - void of any emotional expression. An emotional expression not connected to a thought is an acting lie.
The only way to secure successful recognizable transmission of thought is to understand the emotional connection you have to your opinions and/or ideas. This emotional connection is what the camera picks up as you think your thoughts. For example, the slight tension in the eyelids or ridge of the lips that may be produced by the hint of anger when someone mentions the name of the lover who dumped you. Or the raising of the upper lip in disgust as you watch a cruel parent mistreating their child. To understand the emotional connection you must understand emotions themselves, what triggers them and what they look and feel like on your face.
So, in answer to the statement, ‘All I have to do is think the thought and it will appear on my face’ Is it a myth or a fact? It's a little more complicated. It will happen if the thought is connected to a strong enough idea or opinion and you understand how to communicate these ideas or opinions through the subtleties of emotional facial expression. If you don’t know how to do this then it just won't happen...
My suggestion for all the actors who are trying to make that transition from
stage to on-camera work is to understand and identify these emotional subtleties. In doing so you will become a true storyteller, not only of action, but of thought.