Size Constancy

We perceive objects as having a constant size, even while our distance from them varies.

When we view the NYC sky line from a distance, we know the buildings are enormous, even though they would seem tiny if we held our hand out next to the view.  Our brains know the buildings in the background are tall, because of they are deep in our visual field.

Convergence (Binocular Cue)

Convergence is a neuromuscular cue caused by the eyes' greater inward turn when they view a near object.

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Because her finger is close to her face, the girls eyes' turn inward to look at it. This is an example of convergence. 

Retinal Disparity (Binocular Cue)

Human eyes receive slightly different images because of the distance apart they are. The brain compares the two images, and the difference is called Retinal Disparity. It's an important cue to the relative distance of different objects.

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When you hold your two index fingers in front of your eyes, like the boy, you should see a floating "finger sausage". This is called the retinal disparity. It comes from your two retinas seeing different things.

Visual Illusions

Visual illusions involve visual deception. Due to the arrangement of images, effect of colors, impact of light source or other variable, a wide range of misleading visual effects can be seen.

Example 1:

This insect uses visual deception to evade its predators.  When first looking at this insect, many animals (and humans too!) would think he was a leaf.

Example 2:

Believe it or not, this building is simply made out of parallel lines and staggering blocks.  Because of visual deception though, our eyes view the lines as sloping and the building as crooked.  The contrast of the black and white colors come into affect as well, because if other colors were used the effect would go away.

Example 3:

This faucet with running water appears to our eyes as though it is floating.  Our eyes deceive us and make us wander how there is enough water pressure to be holding a faucet that high up in the sky. In reality, there is a very big tube down the middle of it that holds the structure up.

Texture Gradient (Monocular Cue Cont.)

Texture gradient is when a gradual change from a coarse or distinct texture to a fine, indistinct texture signals increasing distance.
Objects far away appear smaller and more densely packed.


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The flowers' texture in this photograph grows more and more indistinct until all you can really pick out is the color red. This indicates distance.

Interposition (Monocular Cue Cont.)

Interposition is when one object partially blocks our view of another, we perceive the blocked object as farther away and the object blocking to be closer.

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In this photograph of some baby penguins, there are three that are blocking the others partially, making them seem closer to the camera than the ones that are behind them.

Perceptual Constancies: Shape Constancy

Sometimes an object whose actual shape cannot change seems to change with the angle of our view. We perceive the form of familiar objects as constant even while our retinal images of them change.













Even though our view of the cereal box changes in these images, we still maintain that the cereal box has a box-like shape. The different angles of the cereal boxes causes a change of shape on our retinas, but our brains are still able to retain its box-like configuration.