In the image below, you will see a selection of coloured words. The idea of this effect is to say the COLOUR of the word. You will find as you continue to say the colour of the words as you read them, you will slow down. This is because the brain takes a little more time to process conflicting information.
This is called the 'Stroop' effect named after J. Ridley Stroop in the 1930's.
After pressing start, a series of about 12 coloured words will appear after each other, see if you can keep up by saying the correct COLOUR of each word as it appears.
The reason it's difficult:
We are so used to reading, that when we are subject to coloured text of conflicting information i.e. BLUE, RED, GREEN the reading takes precedence over the much less practiced skill of saying the colour.