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.
correct this question
Debbie Fox
reach: rather globalgeometryillusionsmathematicsoptical illusionstechnology
square
rhomboid
concave square
concave rhomboid
answers
flagSwitzerland
84%
3%
9%
3%
65
flagNorway
79%
7%
7%
5%
79
flagSpain
78%
0%
16%
6%
50
flagthe Netherlands
77%
7%
11%
2%
131
flagPoland
75%
10%
7%
5%
35055
flagSweden
74%
8%
9%
8%
62
flagUkraine
74%
7%
2%
10%
39
flagthe United Kingdom
73%
7%
11%
6%
836
flagGermany
72%
9%
8%
7%
437
flagItaly
72%
13%
7%
6%
65
flagthe United Arab Emirates
71%
11%
9%
7%
53
flagFrance
70%
9%
12%
7%
99
flagCanada
70%
12%
11%
3%
88
flagDenmark
69%
11%
16%
2%
42
flagthe United States
68%
10%
11%
6%
1242
flagRepublic of Ireland
67%
7%
9%
13%
95
flagAustralia
67%
12%
6%
13%
79
flagUnknown
66%
15%
9%
7%
2022
flagIndia
53%
11%
17%
14%
317
flagthe Philippines
45%
9%
19%
22%
61