People can process short sentences and solve equations before they're aware of the words and numbers in front of their eyes, finds new research that suggests we might not actually need full consciousness to perform rule-based tasks like reading and arithmetic.

In a series of experiments at the Hebrew University of Jerusalem, more than 300 student participants were unconsciously exposed to words and equations through a research technique known as Continuous Flash Suppression (CFS). With this method, a static image appears in front of one eye while rapidly changing pictures flash in front of the other eye. The changing pictures dominate awareness at first, letting the still image register subliminally before popping into consciousness.

In the first part of the study, one eye was presented with a static phrase or sentence, which was "masked" by changing colorful shapes flashing in front of the other eye. The students were instructed to press a button as soon as they became aware of the words. It usually took about a second, but negative phrases like "human trafficking" and jarring sentences such as "I ironed the coffee" typically registered quicker than positive expressions and more coherent phrases such as "I ironed clothes," the study found.

The researchers say these results suggest that the sentences were fully read and comprehended subconsciously, and certain phrases broke out of suppression faster because they were more surprising.

In the second part of the study, the scientists examined how the unconscious brain processes math problems. Using the CFS technique again, the researchers subliminally exposed the participants to three-digit equations, such as "9 − 3 − 4," for two seconds or less. Then, the participants were shown a number (without CFS masking it) and told to say it out loud. The students were quicker to read aloud a number that was the right answer to the equation they had just subconsciously seen. For example, after being exposed to "9 − 3 − 4," they were quicker to pronounce "2" than "3." This suggests they subconsciously worked out the problem and had the answer on their lips.

Other recent studies have shown that humans might be able to unconsciously perform tasks that have typically been associated with consciousness, such as learning and forming intuitions. The new study adds complex, rule-based operations to that list.

Psychology researcher Ran Hassin, who was involved in the study, said the results suggest current theories about unconscious processes need to be revised.

"These revisions would bring us closer to solving one of the biggest scientific mysteries of the 21st century: What are the functions of human consciousness?"

The research was published this week in the journal Proceedings of the National Academy of Sciences.

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