On 2015 Sep 04, Lydia Maniatis commented:

Lower region was not a new cue in 2002. Rubin discussed it in his article "Visual wahrgenommene Figuren" (1921). I haven't read it, but Kohler mentions it in a book called "Dynamics in Psychology" ((1940): "Rubin found that in such cases certain rules decide which part will preferably acquire the figure-character. One of these rules says that, if two adjacent areas appear one above the other, and if no other principle interferes, the lower part rather than the upper will be seen as shaped and as substantial" (p. 23).

It might be worth translating Rubin's original work into English.

On 2015 Sep 04, Lydia Maniatis commented:

Lower region was not a new cue in 2002. Rubin discussed it in his article "Visual wahrgenommene Figuren" (1921). I haven't read it, but Kohler mentions it in a book called "Dynamics in Psychology" ((1940): "Rubin found that in such cases certain rules decide which part will preferably acquire the figure-character. One of these rules says that, if two adjacent areas appear one above the other, and if no other principle interferes, the lower part rather than the upper will be seen as shaped and as substantial" (p. 23).

It might be worth translating Rubin's original work into English.