When Toy Story's Woody the Cowboy sails off on a hang-glider or Avatar's Jake Sully jumps off a cliff on the back of a giant flying bird, some filmgoers close their eyes and clutch their stomachs. Why does 3-D make some people queasy?
It's all about the "sensory mismatch" that occurs when the brain gets conflicting information from different senses, says Robert Stern, a professor of psychology at Penn State. Think of a kid in a car whose inner ear, which senses motion, detects curves and acceleration, while her eyes see the back of the driver's seat, which doesn't look like it is moving. "Anything that increases sensory mismatch, with different information going into the brain from different senses, increases the incidence of motion sickness in susceptible people," says Stern. The result is nausea, probably because when the brain receives confusing sensory input, "it thinks you may have just ingested a toxin, and decides to get rid of it by vomiting."
The problem with 3-D movies is that we are seeing extremely convincing scenes of motion but we aren't moving ourselves. This causes the sensory mismatch that confuses the brain. "Someone from Kodak asked me how people who are sitting perfectly still in a movie theatre can get motion sickness," says Stern. "They are concerned because when some people watch their large-screen IMAX films, they feel nauseated."
Unfortunately, he notes, there's no easy fix. In fact, if you are susceptible to motion sickness (and Stern's research shows this may have a genetic component) it will only get worse, as Hollywood pushes 3-D technology to the limit. "The visual information is already so realistic, and they are working on making it even more so," says Stern. The brain expects movement to accompany the vivid scenes on screen, and without it "that sensory mismatch is going to make people sick." Studies show that dried ginger root in capsule form helps with the nausea, and eating a high-protein snack every two hours may also minimize symptoms.
Stern hasn't seen Avatar or Toy Story 3 or any of the new crop of 3-D movies, although he once saw a film that used the old 3-D technology, complete with cardboard glasses with different colored lenses. The experience didn't make a big impression on him. Notes Stern, "The movie itself was so bad I don't even remember if the 3-D part made me sick."
Robert M. Stern, Ph.D, is an emeritus distinguished professor of Psychology in the College of the Liberal Arts, rs3@psu.edu. For more information see Chapter 15 in upcoming book, "Nausea: Mechanisms and Management," by R.M. Stern, K.L. Koch, and P.L.R. Andrews (Oxford U. Press).