A new headset system picks up electrical activity from the brain, as well as from facial muscles and other spots, and translates it into on-screen commands. This lets players vanquish villains not with a click, but with a thought. Put on the headset, made by Emotiv Systems in San Francisco, and when a giant boulder blocks the path in a game you are playing, you can levitate it — not by something as crude as a keystroke, but just by concentrating on raising it, said Tan Le, Emotiv's president. The headset captures electrical signals when you concentrate; then the computer processes these signals and pairs a screen action with them, like lifting a stone or repairing a falling bridge.

The headset is the consumer cousin of brain-computer interfaces developed in research labs and used, for example, by monkeys who manipulate prosthetic arms with thoughts. The monkeys’ intentions are detected by sensors, translated into machine language and used to move the arm. In general, some interfaces use sensors implanted directly in the brain; others use electrode-studded caps.

For humans, Emotiv plans to have its noninvasive, wireless EPOC headset ($299) on sale in time for Christmas, Ms. Le said. With 16 sensors that lightly touch the head, it uses a standard technology, electroencephalography, or EEG, to pick up electrical signals from the scalp's surface and convert them to actions that control or enhance what happens on screen.

To help players master the art of moving on-screen objects solely through concentration, the headset will come bundled with a game, set on a magical mountain, that includes practice exercises, said Geoffrey Mackellar, Emotiv's research and development manager. "You clear the mind," he said, and then do 30 to 40 seconds of training, by concentrating, for instance, on visualizing a block lifting from the earth. "On the first or second attempt, you can lift it at will."

Other, harder challenges follow. In constant feedback, he said, the machine learns more about how users think just as users grow more skillful at concentrating.