The thing about illusions is, they trick you even when you know why. Understanding that you are making a visual error doesn’t help you to correct it.

Below are some examples of illusions.  There are also some visual stimuli where the figure and ground swap depending on which part of the picture you focus on. Some of the visual stimuli below promote more than one possible interpretation, either through the figure-ground swap or because they are ambiguous in some other way.

To watch the video below, you will need to click on the link and go to Youtube.
http://www.youtube.com/watch?v=4u64HDXoKVM&feature=related

These so-called ambiguous figures show how the visual system works. Our expectations influence what we ultimately perceive; they also lead us to and make hypotheses about what we are seeing and test them until the evidence before our eyes matches our hypothesis.

More examples of illusions, ambiguous stimuli and other visual phenomena are shown below.

♦For each one, observe whether your way of perceiving it is always the same. Do you find yourself switching from one organisation or interpretation to another?

If so, this image is serving to illustrate for you the way in which humans make hypotheses about the visual stimuli before them, imposing meanings on the stimuli according to expectation, experience or motivation. The context in which the stimulus appears can also influence how we interpret it.


The Necker Cube, kindly provided by http://www.wpclipart.com

Illusions and ambiguous figures also illustrate the difference between visual sensation and visual perception. In the case of ambiguous figures, we are receiving the same pattern of light energy, converting it and shooting it off to the brain in exactly the same way, yet the brain can organise that sensory information in more than one way. One set of visual sensations can yield more than one possible perception.


The Relative Size Illusion, kindly provided by http://www.wpclipart.com

The famous figure-ground swapping Rubin's vase - or is it two faces? Picture provided by www.wpclipart.com

The famous figure-ground swapping Rubin's vase - or is it two faces? Picture provided by www.wpclipart.com

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