In this image, you can see a change quite clearly. The human visual system is very good at detecting such events. Even if you weren't initially fixating the region of the change with your narrow field of high-resolution vision (the fovea), the low-resolution peripheral field is well suited to detecting the flicker and subsequently a saccade would be executed to bring the changing area to the centre of attention.

In the next step of the demonstration, you can see how easily our threshold for detecting such changes can be raised. You will see two alternating frames of an image as above, but in between each image there will be a brief (100 millisecond) interruption in which the entire image turns grey. Try to see if you can detect the change in the image...

Go to the next step in the demonstration...