How is this polygon called? (the one over the circles)

square
rhomboid
concave square
concave rhomboid
In this Ehren­stein illusion the sides of a square placed inside a pattern of con­cen­tric circles take an apparent curved shape. But in reality, the sides are straight.

Answers distribution

square
rhomboid
concave square
concave rhomboid
answers
flagFinland
96%
0%
0%
3%
29
flagCzech Republic
83%
10%
3%
3%
30
flagSpain
80%
0%
14%
4%
41
flagNorway
78%
8%
8%
3%
57
flagPoland
75%
10%
8%
5%
21431
flagthe Netherlands
75%
7%
15%
1%
76
flagthe United Kingdom
72%
8%
12%
5%
627
flagGermany
72%
10%
8%
7%
298
flagItaly
72%
16%
8%
4%
50
flagFrance
70%
8%
11%
7%
79
flagCanada
70%
12%
12%
4%
74
flagthe United States
69%
10%
11%
6%
1050
flagUnknown
68%
13%
11%
5%
117
flagAustralia
68%
12%
7%
12%
57
flagthe United Arab Emirates
67%
10%
10%
10%
37
flagSweden
67%
14%
10%
7%
28
flagRepublic of Ireland
66%
8%
8%
12%
78
flagDenmark
63%
13%
20%
3%
30
flagIndia
55%
9%
17%
13%
252
flagthe Philippines
46%
8%
15%
28%
45

Gender

men76%
women75%
square
76%
75%
rhomboid
10%
10%
concave square
7%
7%
concave rhomboid
5%
5%

Language versions

question
answers
results
flag
How is this polygon called? (the one over the circles)
2058
65%

Details

Author: Debbie Fox
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