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
0%
8%
73%
18%
49
flagthe United Kingdom
4%
7%
72%
14%
421
flagthe United Arab Emirates
10%
7%
71%
7%
28
flagPoland
4%
8%
70%
16%
16302
flagFrance
0%
7%
69%
19%
52
flagUnknown
2%
8%
68%
20%
1224
flagNorway
3%
13%
65%
17%
29
flagSweden
10%
0%
65%
25%
20
flagthe United States
5%
7%
64%
20%
803
flagGermany
5%
13%
64%
15%
195
flagItaly
9%
12%
62%
15%
32
flagCanada
4%
9%
59%
22%
62
flagthe Netherlands
7%
5%
58%
23%
51
flagthe Philippines
3%
9%
58%
25%
31
flagDenmark
15%
10%
57%
15%
19
flagRepublic of Ireland
6%
9%
55%
27%
43
flagIndia
6%
12%
53%
23%
216
flagSouth Africa
0%
29%
47%
17%
17

Gender

men68%
women73%
blue and red only
4%
4%
green and red only
8%
6%
green, blue and red
68%
73%
none
19%
15%

Language versions

question
answers
results
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Which lines are parallel?
1676
63%

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