Psychology: Perceptual Illusions

Perceptual Organization (based on Gestalt Psychology): Gestalt schools of psychology say that people perceive and experience objects as whole patterns. We don't focus on parts but rather we see them as part of the whole. Perceptual organization is a process involving distinction of "figures" from the "ground". Figures are the objects or parts perceived to stand apart from the background. Ground is the background against which the figure appears.
Visual Illusion: is a situation where the sensory cues create perceptual experiences that may (or may not) correspond to what is out there in the real world.

Observe the following drawing for few seconds. Try to see which ladders are going up and which are going down.

What do you see below? Do you see a young woman or an old woman?
Well you can see both a young and an old woman. It depends where you focus your attention on.

Do you see the black devils in this drawing that come to get you? Are you also able to see the white angels that come to rescue you? It depends on which of the two is perceived as the figure and which as the ground.

Do you see a spotted dog here? Why? Someone can claim that he/she sees black spots scattered all over the place. Why do we then see the dog? This is a Gestalt example that we don't see parts but we organize the parts and perceive them as a whole. We always try to organize (give meaning) to whatever information (raw data) we receive.

Another reversible figure that conforms the Gestalt principles of figure and ground. If you focus on the white middle part of the drawing you can see a vase. But if you focus on the blue part on the two sides of the drawing you can see two faces staring at each other.

Trident Optical Illusion: In this case, we go beyond what is sensed (blue lines on flat white surface) to perceive a three-dimensional object that isn't really there.

Muller-Lyer Illusion: Even though the bottom line shows to be longer than the upper one, they actually have the same length. The angular cues at the ends distort their real length. The angles turning inside make the line appear shorter but the angles turning outside make it appear longer.

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