Why is a thinner eyebrow better than a thicker one?

A survey was conducted among 163 women and 38 men (Hwang and Kim, 2018). They were asked to view illustrations of the 4 brow thickness levels and to choose which they thought were ideal, young-looking, healthy-looking, and sexy-looking. Brow thickness was defined in reference to the width of the palpebral fissure (eye width), as follows:

1.Thick(Tk - 1 / 3): the thickness of the eyebrow is 1 / 3(33 %) of the eye width at the lateral canthus.
2.Medium(Med - 1 / 4): the thickness of the eyebrow is 1 / 4(25 %) of the eye width at the lateral canthus.
3.Thin(Tn - 1 / 5): the thickness of the eyebrow is 1 / 5(20 %) of the eye width at the lateral canthus.
4.Very thin(VTn - 1 / 6): the thickness of the eyebrow is 1 / 6(16 %) of the eye width at the lateral canthus.

Results demonstrated that medium brow thickness(med-1 / 4(61.2 %, 123)) was significantly preferred over thick brow. Though thick brow was most often(40.8 %, 82) considered young-looking, there was no significant difference between thick and medium(35.3 %, 71) brow thickness. Thick brow(48.8 %, 98) was most often considered to be healthy - looking, followed by medium brow thickness(30.8 %, 62).On the other hand, thin brow was most commonly considered to be sexy - looking(40.8 %, 82), followed by very thin brows(25.9 %, 52).