Optical illusions are fascinating for a number of reasons. They provide us with a visual illustration of how our minds work. They provide us with the typical 'aha' moment--a moment of insight of a humorous nature. They also provide us with a little diversion from the tedium of the everyday world, where things like optical illusions do not (as a rule) exist.

Most of these optical tricks will solve themselves if you just look at them patiently for a few seconds or so, (however some, like the first, require much more than a few seconds!)

If they don't instantly start giving up their secrets , try blinking or closing your eyes for a few seconds.

Another technique I use is to let my gaze rove gently over the picture and allow yourself to focus on different parts of the puzzle. As you do so you will find different aspects, colours, shapes and patterns will present themselves to you that you may not have seen the first time.

If you are patient you will enjoy the 'aha' moment. It will come if you relax and don't force it. There is no time limit to seeing these illusions with their extra optical dimensions. ( It is not an intelligence test.) Just something you should have fun exploring!

One explanation of just why these illusions work, is found in the German word "Gestalt" meaning "whole". The brain has evolved, according to this theory, to complete things on it's own that it perceives to be missing from what it sees.

That is to say the eye takes in some perception, it 'cognizes' some thing in the environment which is not recognizable for one reason or another, and the brain then makes up the difference so to speak, filling-in the missing part, or what I takes to be the missing part, (according to it's innate programming) and sends the signal or the message to consciousness that this missing thing is such and such.

This can be more easily seen with an illustration. In the figure to the right, you can see that there is clearly no 'actual' triangle drawn there. However, your brain most certainly DOES see one! This is an instance of the brain's need to make a Gestalt out of what it sees from the environment (environment being anything outside of the eyes which the eyes perceives...things, pictures, etc.)

The illusion of course is created for us when we 'realize' the ambiguity of there being a triangle there, to our perception, but at the same time, we know that objectively there is NO triangle drawn there.

This is the basis of how all cognitively based optical illusions work.