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%
4%
92%
4%
25
flagSpain
4%
8%
75%
8%
24
flagAustralia
1%
7%
73%
17%
52
flagSwitzerland
0%
7%
73%
19%
26
flagthe United Kingdom
4%
7%
71%
14%
464
flagSweden
5%
2%
71%
20%
35
flagPoland
4%
8%
70%
16%
18505
flagthe United Arab Emirates
13%
6%
70%
6%
30
flagFrance
0%
8%
69%
17%
62
flagUnknown
2%
8%
67%
20%
1357
flagNorway
3%
16%
64%
16%
31
flagthe United States
5%
8%
63%
20%
836
flagthe Netherlands
8%
7%
63%
18%
71
flagItaly
8%
13%
63%
13%
36
flagGermany
5%
13%
62%
18%
222
flagDenmark
17%
8%
60%
13%
23
flagCanada
4%
10%
58%
23%
65
flagRepublic of Ireland
6%
8%
57%
27%
47
flagthe Philippines
6%
9%
54%
27%
33
flagIndia
7%
12%
53%
22%
238

Gender

men68%
women74%
blue and red only
4%
4%
green and red only
8%
6%
green, blue and red
68%
74%
none
19%
14%

Language versions

question
answers
results
flag
Which lines are parallel?
1790
63%

Details

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