However, the tricks that our brains learn can sometimes allow us to be fooled by things that don’t follow the rules the tricks are supposed to help us with. For example, the picture above shows four Pac Man objects but we see a square. This would be a very useful skill if a square was being blocked by an object because we would know that the square still exists behind the object. Our brains are tricked into seeing a square because they assume the square is being blocked by an object even when it is not. If we had never seen objects being blocked this would not happen and we would only see Pac Men.
To understand this a little further let me tell you a story about cats. These cats were raised in a cage with only vertical or horizontal lines.
After their upbringing they were allowed to come out of their cages but were unable to “see” the type of lines that were not in their cages while they were growing (Myers, 2000). For example, if raised in a vertical line cage they would play with a rod held vertically but not horizontally and vice versa.
There are many other tricks our visual perception plays on us but for each example of visual illusions there is a visual short cut that we are using and that we learn by growing up in this world. Another example, is the following problem. Which line is the longest?
Our brain thinks that the line on the bottom is longer but that is only because we have had experience with corners of rooms.
If we look at the picture above we can easily tell which is the tallest line and which is the shortest because of the shape of the lines that come out of the top of the vertical lines.
When we see lines like this
They look closer to us because of our experience with corners coming at us.
However, if we see a line this
It looks further away because of our experience with corners of rooms far away from us.
The perception of the first line being closer and the second line being further away creates the illusion that one is bigger then the other. Remember that these illusions are experience dependent.