Israeli scientists: We've mapped unconscious human thought

Seventy years after the death of Sigmund Freud, researchers from Tel Aviv University say they have outlined unconscious thought and can even characterize the cerebral activity behind it.

Freud, the Austrian-Jewish neurologist who revolutionized the way we view the human mind, studied the human defense mechanism of repression and presumed to reveal a world of unconscious desires and impulses beneath a thin veil of conscious behavior.

As founder of the psychoanalytic school of psychology, Freud argued that the activity of this unconscious existence can be deduced, even if not directly identified. Dreams, he went on to say, were an example of how the unconscious mind manifests itself.

In a study published in the Journal of Cognitive Neuroscience, Moti Salti, Dominique Lamy and Yair Bar-Haim, all of Tel Aviv University's psychology department, stress that the unconscious activity with which their research deals is not identical to the unconscious mind described by Freud in his writings.

"We're not talking about an unconscious existence of traumas and impulses, but about unconscious perception," said Salti. "You walk around and are exposed to many stimuli from all directions, but are aware of few."

The study's aim was to outline the difference between cerebral activity related to conscious perception and activity associated with unconscious perception.

To achieve this, the researchers conducted experiments in which they exposed participants to visual stimulation in the form of a square shape on a computer screen. The researchers tried to identify when the participants saw the square, even as they continued no to be consciously aware of it.

This occurred when participants said they had not seen the square despite it appearing. Asked to guess where the square might have appeared, they were nonetheless able in many cases to point to the exact spot.

Salti says that participants were able to pinpoint the square - which they contended had not appeared - in 50 percent of cases. "This shows the information was processed but was not conscious," he said.

Participants were hooked up to an electroencephalograph, which measures brain activity. The readings showed that consciousness sets in almost half a second after perception. "This means we sometimes feel we want to do things only after we have already done them," suggested Salti.

He added: "On a philosophical level, it raises questions about the concept of volition. It's disturbing on a personal level."