The Third Element: The Power & Nature of Behavior by Lewis Baumander

Behavior more often than not is the most honest “tell” that reveals what we are feeling and thinking without us uttering a word. It reinforces what we are saying or betrays us. We often decide whether someone is lying to us or telling the truth on the basis of observation. Our very safety and well-being depends on how swiftly we can read another’s behavior. Over the span of human history literally thousands of behaviors and gestures have evolved and imprinted themselves into our genetic coding. This guarantees our ability to communicate with one another. Language may be localized, but behavior is universal. 
Crudely, there are two kinds of human behavior. One is called iconic, and the other is called symbolic or representational.
Iconic behavior is universal. 
It affects us deeply and emotionally in a primal way. We experience it chemically. These human behaviors are universally understood independent of language, culture or context. It doesn’t matter what point in history you came from, what language you speak, what race or culture you belong or belonged to there are certain behaviors that are universal.

There’s no defense against an iconic behavior. You can reject it and say to yourself “wait that’s not true,” but it will affect you chemically for a split second. As mentioned above there are 1000s and 1000s of these behaviors and gestures. 
Symbolic behavior or representational behavior changes over time. 
Eventually, symbolic behavior will become universal. For example, raising the middle finger skyward (often referred to as “flipping the bird”). This gesture is pretty iconic now. However there was a time in history when this was symbolic. After a battle, (back when bows and arrows were a mean weapons of mass destruction) the winning side would cut off that middle finger of all the dead archers and send those fingers to the opposing King. So one of the symbolic gestures of an Archer (before they shot their first arrow) was to present their middle finger in the direction of the enemy. Symbolically saying “Still got it. Fuck you!”

Sometimes the meaning of a symbolic behavior or gesture change over time. For Example the “V” sign created by raising the first 2 fingers was symbolic of victory. It was a war symbol. When my father in law(he was an RF pilot) got off his Lancaster Bomber he would raise his 2 fingers as a sign of Victory. My generation turned it into a peace symbol. But be careful in parts of Europe when you reverse it, it will be perceived as a very rude gesture.
What does this have to do with acting?
A great deal! If you can master the use of iconic behavior’s you will start to be able to affect Casting. Like you they are not immune to being impacted by a well-placed and character appropriate iconic behavior. We also have science to back us up here: Muscle Memory and Mirroring Neurons The committed engagement to certain behaviors or gestures will produce a chemical response within you and others. Simply put Emotion is trapped in muscle. Behaviors or gestures will trigger emotional responses and because we have Mirroring Neurons it will trigger associations in others.

When it pertains to symbolic or representational behavior your physical choices may mean different things at different times in history or in different cultures. I can remember a particular casting director. Who was casting a period TV series. It was set in Elizabethan England. She was most annoyed that a lot of young women would come in for roles of sophisticated ladies of the court with hands on hips. They stood with poor posture hips slightly thrust to the left. She told a number of them “you’re a lady of the court, not a barmaid.

A woman stood with that kind of thrusting of one hip, with a hands-on-hips is a contemporary symbol of a bad-ass woman but in Elizabethan England that’s called the prostitute or barmaid.

If you could start to master or become a student of Iconic and Symbolic behaviors and gestures and start to understand when and how to use them, it will make a huge difference to how you could communicate to an audience or casting.