Poggendorff Illusion

A real 'classic' illusion, this is where people find it hard to judge whether the lines outside the rectangle/central stripe will meet or not.

The union jack flag allows for this effect by offsetting the lines of the Saint Patrick's Cross (the red diagonal lines) so that they appear to match up - when actually they don't:

Look at the white spaces (or check them with a ruler!)

Another illusion

Here's another one - shows it works in colour too! The 'yellow' square in the middle of the front face and the 'brown' one in the middle of the top face are the same colour. They are. They really are.

In some ways, examples of how our visual perception can be mislead are simple enough to get your head around. Perhaps it makes you wonder, though, how much of your other perceptions are distorted. Can you think of an argument, for example, when you and another were both convinced that you were right about something, even though you disagreed?

Illusions

Hi,

Talking about illusions in class today - this is one of my favourite ones, and I think it works better on the screen than on paper:

Yes - believe it or not, squares 'A' and 'B' are exactly the same shade of grey.

Illusions like this help us to understand a key idea of the 'cognitive perspective' - the world that we percieve is to a large extent constructed by our mental processes. How we respond to objects and events can depend on our expectations and thought processes.

In this example, we expect square 'A' to be black and square 'B' to be white - so that is what we see!