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
Switzerland
30
France
17
Pakistan
15
Austria
55
Singapore
32
Malaysia
18
Germany
301
Unknown
27
the Netherlands
26
Australia
80
Republic of Ireland
19
Poland
20001
the United Kingdom
242
Greece
24
the United Arab Emirates
28
the United States
790
South Africa
17
India
322
the Philippines
40
Canada
63