Ambiguous image

One of the earliest examples of this type is the rabbit–duck illusion, first published in Fliegende Blätter, a German humor magazine.

[1] Other classic examples are the Rubin vase,[2] and the "My Wife and My Mother-in-Law" drawing, the latter dating from a German postcard of 1888.

[5] Middle vision is the stage in visual processing that combines all the basic features in the scene into distinct, recognizable object groups.

When finding edges, the brain's visual system detects a point on the image with a sharp contrast of lighting.

For example, consider an image that involves an opposite change in magnitude of luminance between the object and the background (e.g. From the top, the background shifts from black to white, and the object shifts from white to black).

The opposing gradients will eventually come to a point where there is an equal degree of luminance of the object and the background.

Although there is no complete image to be seen, the brain is able to accomplish this because of its understanding of the physical world and real incidents of ambiguous lighting.

[8] The visual system accomplishes this by making inferences beyond the information that is presented in much the same way as the luminance gradient.

In mid-level vision, the visual system utilizes a set of heuristic methods, called Gestalt grouping rules, to quickly identify a basic perception of an object that helps to resolve an ambiguity.

[3] This allows perception to be fast and easy by observing patterns and familiar images rather than a slow process of identifying each part of a group.

[6] For example, when looking at a chess board, we perceive a checker pattern and not a set of alternating black and white squares.

This can include unique spatial location, such as two objects occupying a distinct region of space outside of their group's own.

[6] The visual system can also aid itself in resolving ambiguities by detecting the pattern of texture in an image.

This can be due to a shading effect on the edges of one region of texture, giving the appearance of depth.

Street artists often use tricks of point-of-view to create two-dimensional scenes on the ground that appear three-dimensional.

Recognizing an object plays a crucial role in resolving ambiguous images, and relies heavily on memory and prior knowledge.

To counter the problem of viewpoint, the visual system detects familiar components of an object in 3-dimensional space.

[14] Our memory has a large impact on resolving an ambiguous image, as it helps the visual system to identify and recognize objects without having to analyze and categorize them repeatedly.

Without memory and prior knowledge, an image with several groups of similar objects will be difficult to perceive.

[6] The act of priming the participant with an exposure to a similar visual stimulus also has a large effect on the ease of resolving an ambiguity.

[6] From 1903 to 1905 Gustave Verbeek wrote his comic series The Upside Downs of Little Lady Lovekins and Old Man Muffaroo.

In 2012 a remake of a selection of the comics was made by Marcus Ivarsson in the book 'In Uppåner med Lilla Lisen & Gamle Muppen'.

The children's book, Round Trip, by Ann Jonas used ambiguous images in the illustrations, where the reader could read the book front to back normally at first, and then flip it upside down to continue the story and see the pictures in a new perspective.