Schroeder stairs (Schröder's stairs) is an

optical illusion Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide v ...

which is a two-dimensional drawing which may be perceived either as a drawing of a staircase leading from left to right downwards or the same staircase only turned upside down, a classical example of perspective reversal in psychology of perception. It is named after the German

natural scientist Natural science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatabili ...

Heinrich G. F. Schröder Heinrich Georg Friedrich Schröder (28 September 1810 – 12 May 1885) was a German natural scientist (physicist, chemist), mathematician and educator.Alexander KipnisSchröder, Georg Friedrich Heinrich In: Neue Deutsche Biographie (NDB). Band 23, ...

, who published it in 1858.Alwyn Scott, ''Stairway to the Mind: The Controversial New Science of Consciousness''
p. 95
/ref> It is sometimes called "Schouten steps", in reference to a small sheet-metal staircase given to M.C. Escher by Prof. Schouten and which was an inspiration for Escher's "Convex and Concave". This illusion is also seen in another Escher's work, "Relativity". Barile, Margherita.
Schroeder Stairs''
from

Eric W. Weisstein Eric Wolfgang Weisstein (born March 18, 1969) is an American mathematician and encyclopedist who created and maintains the encyclopedias ''MathWorld'' and ''ScienceWorld''. In addition, he is the author of the '' CRC Concise Encyclopedia of M ...

's MathWorld This drawing may be variously described as an "

ambiguous figure Ambiguous images or reversible figures are visual forms that create ambiguity by exploiting graphical similarities and other properties of visual system interpretation between two or more distinct image forms. These are famous for inducing the ...

", " reversible figure" or " bistable figure". The first classification refers to the likelihood that the drawing may be perceived as two (or more) different objects. The second refers to the phenomenon that after some time of staring at the figure the perception of its orientation becomes involuntarily reversed. The third one emphasizes the fact that there are two (rather than one) stable perceptions of the drawing.''Nonlinear Dynamics in the Life and Social Sciences'', edited by William H. Sulis, Irina Nikolaevna Trofimova
p. 315
/ref> This illusion, among others, has been used in studies of perception. In particular, in one study it was established that involuntary switch of perception occurs with approximate frequency of once in 7.5-12.5 seconds. The change of perception may be attributed either to neuronal fatigue or to conscious selection.As cited in ''Nonlinear Dynamics...''

References

{{DEFAULTSORT:Schroeder Stairs Optical illusions Stairways