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
flagSwitzerland
0%
0%
77%
22%
22
flagSpain
4%
8%
75%
8%
24
flagthe United Kingdom
4%
7%
72%
14%
439
flagAustralia
1%
7%
72%
17%
51
flagPoland
4%
8%
70%
16%
17098
flagthe United Arab Emirates
13%
6%
70%
6%
30
flagSweden
8%
0%
70%
20%
24
flagFrance
0%
9%
69%
18%
55
flagUnknown
2%
8%
67%
20%
1274
flagNorway
3%
13%
66%
16%
30
flagthe United States
5%
8%
64%
20%
807
flagGermany
4%
13%
63%
16%
207
flagthe Netherlands
7%
7%
61%
20%
65
flagItaly
9%
15%
60%
15%
33
flagCanada
4%
9%
59%
22%
62
flagDenmark
15%
10%
57%
15%
19
flagRepublic of Ireland
6%
9%
56%
27%
44
flagthe Philippines
6%
9%
56%
25%
32
flagIndia
6%
12%
53%
23%
225

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
flag
Which lines are parallel?
1710
63%

Details

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