From Benjamin K. Bergen's Louder than Words (Basic Books):
Think about the direction you turn the doorknob of your front door. You probably visually simulate hat your hand would look like, but if you're like most people, you do more than this. You are able to virtually feel what it's like to move your hand in the appropriate way—to grasp the handle (with enough force to cause the friction required for it to move with your hand (clockwise, perhaps?) at the wrist. Or if you're a skier, you can imagine not only what it looks like to go down a run, but also what it feels to shift your weight back and forth as you link turns.
Now, in all these examples, you're consciously and intentionally conjuring up simulations. That's called mental imagery. The idea of simulation is something that goes much deeper. Simulation is an iceberg. By constantly reflecting, as you just have been doing, you can see the tip—the intentional, conscious imagery. But many of the same brain processes are engaged, invisibly and unbeknownst to you, beneath the surface during much of your waking and sleeping life. Simulation is the creation of mental experiences of perception and action in the absence of their external manifestation. That is, it's having the experience of seeing without the sights actually being there or having the experience of performing an action without actually moving. When we're consciously aware of them, these simulation experiences feel qualitatively like actual perception, colors appear as they appear hen directly perceived, and actions feel like they feel when we perform them. The theory proposes that embodied simulation makes use of the same parts of the brain that are dedicated to directly interacting with the world. When we simulate seeing, we use the parts of the brain that allow us to see the world: when we simulate performing actions, the parts of the brain that direct physical action light up. The idea is that simulation creates echoes in our brains of previous experiences, attenuated resonances of brain patterns that were awcwtwive during previous perceptual and motor experiences. We use our brains to simulate percepts and actions without actually perceiving or acting.
Outside of the study of language, people use simulation hen they perform lots of different tasks, from remembering facts to listing properties of objects to chroreographing a dance. These behaviors make use of embodied simulation for good reason. It's easier to remember where we left our keys when we imagine the last place we saw them. It's easier to determine what side of the car the gas tank is on by imagining filling it up. It's easier to create a new series of movements by first imagining performing them ourselves. Using embodied simulation for rehearsal even helps people improve at repetitive tasks, like shooting free throws and bowling strikes. People are simulating constantly.
