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%
87%
6%
16
flagAustralia
0%
6%
77%
15%
45
flagSpain
4%
9%
77%
4%
22
flagFrance
0%
6%
72%
17%
47
flagthe United Kingdom
4%
7%
71%
14%
363
flagPoland
5%
9%
69%
14%
11192
flagthe United Arab Emirates
11%
7%
69%
7%
26
flagUnknown
8%
5%
68%
16%
67
flagIndonesia
0%
0%
66%
33%
15
flagNorway
4%
17%
65%
13%
23
flagthe United States
5%
8%
64%
20%
781
flagItaly
9%
12%
64%
12%
31
flagGermany
5%
13%
63%
15%
158
flagthe Philippines
3%
3%
59%
29%
27
flagCanada
5%
10%
58%
23%
60
flagthe Netherlands
9%
4%
57%
23%
42
flagIndia
6%
11%
53%
23%
210
flagRepublic of Ireland
7%
10%
52%
30%
40
flagDenmark
21%
7%
50%
21%
14
flagSouth Africa
0%
31%
43%
18%
16

Gender

men68%
women73%
blue and red only
5%
4%
green and red only
10%
7%
green, blue and red
68%
73%
none
16%
14%

Language versions

question
answers
results
flag
Which lines are parallel?
1600
63%

Details

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