<Tr> <Td> Impossible trident </Td> </Tr> <P> An early example of an impossible object comes from Apolinère Enameled, a 1916 advertisement painted by Marcel Duchamp . It depicts a girl painting a bed - frame with white enamelled paint, and deliberately includes conflicting perspective lines, to produce an impossible object . To emphasise the deliberate impossibility of the shape, a piece of the frame is missing . </P> <P> Swedish artist Oscar Reutersvärd was one of the first to deliberately design many impossible objects . He has been called "the father of impossible figures". In 1934 he drew the Penrose triangle, some years before the Penroses . In Reutersvärd's version the sides of the triangle are broken up into cubes . </P> <P> In 1956, British psychiatrist Lionel Penrose and his son, mathematician Roger Penrose, submitted a short article to the British Journal of Psychology titled "Impossible Objects: A Special Type of Visual Illusion". This was illustrated with the Penrose triangle and Penrose stairs . The article referred to Escher, whose work had sparked their interest in the subject, but not Reutersvärd, of whom they were unaware . The article was published in 1958 . </P>

What purpose does it serve for psychologists to study illusions and impossible figures