<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2015) (Learn how and when to remove this template message) </Td> </Tr> <P> Rubin's vase (sometimes known as the Rubin face or the figure--ground vase) is a famous set of ambiguous or bi-stable (i.e., reversing) two - dimensional forms developed around 1915 by the Danish psychologist Edgar Rubin . They were first introduced at large in Rubin's two - volume work, the Danish - language Synsoplevede Figurer ("Visual Figures"), which was very well received; Rubin included a number of examples, such as a Maltese cross figure in black and white, but the one that became the most famous was his vase example, perhaps because the Maltese cross could also be easily interpreted as a black and white beachball . </P>

Where is the negative space in this well known image called the rubin vase