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Scientific News  Biology The theories and researches of life HUMAN EYES CAN BE IN TWO PLACES AT ONCE
HUMAN EYES CAN BE IN TWO PLACES AT
ONCE
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Watch it: our eyes can focus on two places
at the same time |
Students who suspect teachers have eyes in
the back of their heads may be right - in a way: researchers have proven for the
first time that human eyes can focus on more than one point simultaneously.
The German study, which used a sophisticated computer version of the card game 'snap',
asked the 15 subjects to concentrate on a point on a computer screen while four
different symbols were also flashed on the screen. They had to press a button
when they saw two symbols that matched.
Matthias Muller from the University
of Leipzig, who led the study, found that the
subjects were able to identify when there were two matching symbols on different
parts of the screen.
This result helps to answer a long-standing controversy about whether the 'spotlight'
of spatial attention only has one beam, or if it can be divided into several
locations. The results are published in this week's issue of the journal, Nature.
Previous results of many behavioural and electrophysical studies had supported
the single spotlight view. But the new research shows that the brain can
simultaneously focus on multiple regions, rather than just rapidly switching its
attention between them.
The researchers eliminated the possibility of the subjects quickly alternating
their vision between the two symbols by flashing the symbols at a rate of 181
milliseconds (thousands of a second). This is faster than humans can switch
between two locations, which has previously been measured at between 200 and 500
milliseconds.
Each of the symbols was flickering at a different rate, which meant the
researchers could distinguish symbols from one another using their measuring
equipment.
The subjects, who were linked up to 30 scalp electrodes on an elastic cap, were
able to determine when there were two matching symbols - this demonstrates that
human eyes are able to focus on two things at once.
"The present findings provide evidence that the spotlight may be divided
for sustained periods. This would appear to be a highly efficient early
selection mechanism for distributing attention optimally to dispersed stimuli in
the visual surroundings," Muller concluded in his paper.
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Publishing date: July 30, 2003
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