Generally, I know if I'm moving or if the room is moving. There are, however, some interesting failures in knowing which one of us is moving. For example, I pulled up to a stoplight recently with a large tractor-trailer truck in the lane next to me. Although I didn't realize this at first, the truck started rolling forward just a little. Suddenly it felt as if my car and I were rolling backwards. Even though my foot was on the brake, I stomped it harder. Of course, the truck kept rolling and I kept feeling like I was the one moving. Have you ever had this experience? Usually the spell is broken after a few moments; particularly if I turn to look at the truck. Episodes like these demonstrate how important visual information is for the perception of when we are moving versus when things around us are moving.
Some rather creative researchers recreated the truck at the stoplight effect in a series of brilliant studies using a moving room. Yes, researchers have created rooms that move around you. These are some of the funnier studies in cognitive psychology and I hope you'll see why. As far as I know, David Lee and his colleagues created the first moving room experiment back in the 1970s. I've always wondered if the insight for the research came during or after a wild party. Lee and his colleagues created a smaller room with a larger room. Their creation included 3 walls (the front wall and both sides) plus a ceiling. The crucial part is that the whole creation was suspended just above the floor of the real room. In addition, they attached this room to a set of pullies so they could move it ever so slightly - thus the moving room!
Now comes the fun part - people stood in this room facing the front wall. Then the researchers slowly moved the room backwards and forwards. Adults will start to lean backwards and forwards in the opposite direction to the room movement. If you place toddlers in the room and move the room slightly, the toddlers will also start to weave. Of course, toddlers have less experience maintaining their balance, so many will over-compensate, and plop, sit down (no toddlers were hurt).
The truck next to me at the light and the moving room are the same phenomenon. We use motion in our visual perceptual field to allow us to determine whether we are moving or if something in the world is moving. When everything in the visual perceptual field is moving, that specifies that we are actually the thing that is moving - the rest of the world is being swept past as we move forward. This is why the tractor-trailer truck confused me at the stoplight. Everything in my left peripheral visual field was moving so it felt like my car and I were moving. This is why people adjust their posture in the moving room - everything in the world is moving in a unified fashion specifying that they aren't standing erect any longer. This is also why it feels like the moon is following you around. When you walk forward, everything moves past you, except the moon. This specifies to you that the moon is moving with you, or as Cat Stevens put it: I'm being followed by a moon shadow.
You don't need a moving room to experience this. Go to one of those supersized movie theaters, where the screen is so large that some of the motion occurs in your periphery. The effect is most cool with movies of flying in an airplane or riding on a roller coaster. You can watch everyone in the theater leaning into the turns. Watching the same movie on your small TV screen isn't nearly as much fun.
Generally I can tell when I'm moving and when the room around me is moving. The fun, and amusing, exception is when everything in your visual field moves - suddenly it feels like you are moving even when you are standing still.
