The researchers -- led by UCL psychologist Dr. Li Zhaoping -- recruited 10 volunteers for their study. The participants were shown a computer screen with more than 650 identical symbols -- including one upside-down version of the symbol -- and asked to identify on which side of the screen the inverted symbol appeared.
Li and colleagues found that when the participants were given a fraction of a second to look at the screen, they gave the correct answer 95 percent of the time. However, when the subjects were given longer than a second to examine the screen, they were only 70 percent accurate.
"This finding seems counter-intuitive," Li said. "You would expect people to make more accurate decisions when given the time to look properly."
According to Li, the participants were more accurate when making "snap" decisions because the subconscious brain -- which makes rapid, instinctive decisions -- recognized the inverted symbol on the screen as different from the original. Conversely, the conscious brain saw the symbol as identical to the right-side-up symbols, only in a different orientation.
"The conscious or top-level function of the brain, when active, vetoes our initial subconscious decision -- even when it is correct -- leaving us unaware or distrustful of our instincts and at an immediate disadvantage," Li said. "Falling back on our inbuilt, involuntary subconscious processes for certain tasks is actually more effective than using our higher-level cognitive functions."
Psychologist Kim Stephenson, a researcher of decision-making processes, said subconscious reactions evolved from when humans were forced to make snap decisions to quickly escape predators, and may prove more useful than the conscious mind in some situations.
"Your subconscious mind is more useful for specific things, where you don't have time and need to react quickly," he said. "It's not to say that if you've got to make a decision you should make it in a fraction of a second -- that is daft. But your body is designed to do some things very quickly, so using instincts would be better there."