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%
32
flagCzech Republic
83%
10%
3%
3%
30
flagNorway
81%
7%
7%
4%
69
flagSpain
79%
0%
14%
6%
48
flagthe Netherlands
75%
7%
14%
2%
89
flagPoland
74%
10%
8%
5%
28555
flagGermany
73%
8%
8%
7%
345
flagItaly
73%
14%
7%
5%
56
flagthe United Kingdom
72%
7%
12%
5%
719
flagCanada
70%
11%
12%
3%
77
flagthe United Arab Emirates
70%
9%
9%
9%
41
flagthe United States
69%
10%
11%
5%
1096
flagFrance
69%
9%
12%
7%
85
flagAustralia
68%
10%
7%
13%
66
flagUnknown
67%
14%
9%
7%
1681
flagRepublic of Ireland
67%
8%
8%
13%
82
flagDenmark
66%
12%
18%
3%
33
flagSweden
61%
11%
14%
11%
34
flagIndia
55%
9%
17%
14%
259
flagthe Philippines
48%
8%
16%
26%
49

Gender

men72%
women76%
square
72%
76%
rhomboid
12%
10%
concave square
8%
7%
concave rhomboid
6%
5%

Language versions

question
answers
results
flag
How is this polygon called? (the one over the circles)
2187
65%

Details

Author: Debbie Fox
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