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!

Answers distribution

blue and red only
green and red only
green, blue and red
none
answers
flagCroatia
0%
6%
86%
6%
15
flagAustralia
0%
6%
77%
15%
45
flagSpain
4%
9%
77%
4%
22
flagthe United Kingdom
4%
7%
71%
13%
345
flagFrance
0%
6%
70%
18%
44
flagPoland
5%
9%
69%
15%
10773
flagthe United Arab Emirates
13%
8%
69%
8%
23
flagUnknown
8%
6%
68%
17%
47
flagItaly
6%
13%
66%
13%
30
flagIndonesia
0%
0%
66%
33%
15
flagGermany
5%
14%
64%
14%
152
flagFinland
14%
21%
64%
0%
14
flagthe United States
5%
7%
63%
21%
771
flagNorway
4%
18%
63%
13%
22
flagthe Philippines
3%
3%
59%
29%
27
flagCanada
5%
10%
57%
22%
57
flagthe Netherlands
9%
4%
57%
23%
42
flagIndia
6%
12%
53%
22%
205
flagRepublic of Ireland
7%
10%
52%
30%
40
flagSouth Africa
0%
31%
43%
18%
16

Gender

men68%
women72%
blue and red only
5%
4%
green and red only
10%
7%
green, blue and red
68%
72%
none
16%
14%

Language versions

question
answers
results
flag
Which lines are parallel?
1568
63%

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