<< If the foot touching the ground is perceived to be the left foot, the dancer appears to be spinning clockwise (if seen from above); >>
<< if it is taken to be the right foot, then she appears to be spinning counterclockwise >>
<< the way people perceive the Silhouette Illusion , a popular illusion that went viral and has received substantial online attention, has little to do with the viewers' personality, or whether they are left- or right-brained, despite the fact that the illusion is often used to test these attributes in popular e-quizzes >>
<< Niko Troje says that a reported preference for seeing the silhouette spinning clockwise rather than counter-clockwise is dependent upon the angle at which the viewer is seeing the image >>
<< Our visual system, if it has a choice, seems to prefer the view from above >>
New study debunks myth about popular optical illusion (Update). Dec. 21, 2010
https://m.medicalxpress.com/news/2010-12-debunks-myth-popular-optical-illusion.html
Nikolaus F Troje, Matthew McAdam. The Viewing-from-Above Bias and the Silhouette Illusion. Jan. 1, 2010
http://journals.sagepub.com/doi/abs/10.1068/i0408
also:
https://www.ncbi.nlm.nih.gov/m/pubmed/?term=silhouette+illusion