Confused Perceptions

Gestalt Theory

Confused perceptions

Visual illusions occur when our perception conflicts with reality. We are not seeing the world as it really is. We see an illusion when we misinterpret the stimulus, so the physical reality and our perception disagree. There are three main types:

· Fictions

· After effects (not included in the three main)

· Ambiguous Figures

· Distortions

Fictions

A fiction illusion occurs when you perceive a shape that is not there. Sometimes we perceive edge and believe that a shape exists when there is no actual boundary.

If you look at the illustration below you will see 2 triangles in the centre of the images.

This is a fiction as there is no physical triangle in the stimulus. This is called an illusory contour. You perceive a contour or edge that isn’t really there in the stimulus, so it is an illusion.

After effects

A special group of illusion are called after-effects. They are like fictions because they involve perceiving something like movement or a shape that is not in the stimulus. This happens when we look at a stimulus for a long time then look away. The after-effect is a perception that is the opposite of the stimulus.. Imagine staring at a picture of a white cat on a black background. The opposite would be a white cat on a black background and this is what the after-effect would look like.

Count to 20 staring at the queen’s nose then look at the empty space beside, what can you see?

You can experience a motion after-effect at the end of a film. When the credits roll, watch the words moving upwards. If you look to the side of the screen when they end, the wall or curtains will appear to move downwards! This is because you are perceiving movement in the opposite direction from the stimulus.

Ambiguous figures

When a figure is ambiguous, you can only perceive one of the possible interpretations at a time. You can often swap between the two alternatives. Think of the Neckar Cube. You can see it either as a see-through box with a red dot at the back, or a solid box with a red dot on the front.

With the Necker Cube at least one of the interpretations is possible to see. For some it is hard to see the alternative.

Distortions

Knowing what you are seeing is wrong, is one way to describe a distortion illusion. Look at the two images below to help understand that:

It happens when our perception is deceived by some aspect of the stimulus. A straight line may be perceived as curved, or a shape may look bigger or smaller than it really is.