Fishing in the stream of consciousness, researchers now can detect our intentions and predict our choices before we are aware of them ourselves. The brain, they have found, appears to make up its mind 10 seconds before we become conscious of a decision -- an eternity at the speed of thought.

Their findings challenge conventional notions of choice.

"We think our decisions are conscious," said neuroscientist John-Dylan Haynes at the Bernstein Center for Computational Neuroscience in Berlin, who is pioneering this research. "But these data show that consciousness is just the tip of the iceberg. This doesn't rule out free will, but it does make it implausible."

Through a series of intriguing experiments, scientists in Germany, Norway and the U.S. have analyzed the distinctive cerebral activity that foreshadows our choices. They have tracked telltale waves of change through the cells that orchestrate our memory, language, reason and self-awareness.

In ways we are only beginning to understand, the synapses and neurons in the human nervous system work in concert to perceive the world around them, to learn from their perceptions, to remember important experiences, to plan ahead, and to decide and act on incomplete information. In a rudimentary way, they predetermine our choices.