I asked 50 people to which of the below images was the "illusion." This was of course entirely subjective:

Image A:

4652244142_95c422435c_b

or Image B:

The results: the images were split in terms of which was the "illusion" (26 A vs 24 B), but those who said image B took longer to do so (28.9 seconds on average for A vs 37.9 seconds on average for B).

Was just a simple thing that came to mind while taking the Pierley/Redford Dissociative Affect Diagnostic.  

See the CSV of results here