Which lines are parallel?
blue and red only
green and red only
green, blue and red
none
This is a well known Zöllner illusion, first described in 1860. It may be caused by this impression of depth. The black lines are parallel, too!
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Answers by country
blue and red only
green and red only
green, blue and red
none
answers
Switzerland34
France17
Pakistan15
Austria59
Singapore32
Malaysia18
Unknown27
the Netherlands27
Australia82
Republic of Ireland19
Poland20143
Germany339
the United Kingdom249
Greece26
the United Arab Emirates28
the United States820
South Africa17
India327
the Philippines40
Canada63