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
flagSwitzerland
81%
3%
10%
3%
55
flagNorway
80%
6%
7%
5%
78
flagthe Netherlands
78%
7%
11%
1%
123
flagSpain
78%
0%
16%
6%
50
flagPoland
74%
10%
8%
5%
33205
flagSweden
73%
8%
9%
8%
61
flagthe United Kingdom
72%
7%
12%
6%
800
flagGermany
72%
9%
8%
7%
412
flagCroatia
72%
10%
10%
0%
37
flagItaly
71%
14%
7%
6%
64
flagFrance
70%
9%
12%
7%
97
flagCanada
70%
12%
11%
3%
87
flagthe United Arab Emirates
70%
12%
10%
8%
50
flagDenmark
70%
10%
17%
2%
40
flagthe United States
69%
10%
11%
6%
1174
flagAustralia
68%
12%
6%
12%
73
flagUnknown
67%
15%
9%
7%
1953
flagRepublic of Ireland
66%
7%
9%
13%
93
flagIndia
54%
10%
16%
15%
298
flagthe Philippines
45%
9%
18%
24%
53

Gender

men72%
women77%
square
72%
77%
rhomboid
12%
10%
concave square
8%
7%
concave rhomboid
6%
5%

Language versions

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answers
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How is this polygon called? (the one over the circles)
2413
64%

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Author: Debbie Fox
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