Images Dated 31st August 2004

Wundt illusion

Wundt illusion. This illusion was created by the psychologist Willhelm Wundt in the 19th century. It is the exact opposite of the Hering illusion. It exploits the brain's understanding of perspective to fool it into thinking that the two horizontal red lines bow inwards. In fact they are straight and parallel. This is achieved due to the presence of the grey lines radiating from 2 points. They give the appearance of depth, with the middle of the image appearing closer than the top. The brain compensates for this, and the illusion is created

© SCIENCE PHOTO LIBRARY

Zoellner illusion

Zoellner illusion. The vertical lines are parallel but seem to be tilted. There are 2 theories as to why this is the case. The first is that the small crossing lines create a perception of depth and our brain's interpretation of perspective leads to the illusion. The second is that the effect is a result of our visual system's propensity to try to minimise acute angles - applied to the small crossing lines

© SCIENCE PHOTO LIBRARY

Researcher testing Lego robots playing Pacman

Lego Pacman game. Researcher testing a three dimensional game of Pacman played by Lego robots. In this game the player operates the "good" yellow robot by remote control whilst the "bad" red robots will automatically try to capture it. The game is played in a maze marked out with black lines on a white background. The red robots are controlled by Mindstorm computer Lego bricks which are programmed to chase and capture the yellow robot. The red robots negotiate the maze with the help of optical sensors that recognize the black lines. The bad robots also have optical sensors that help them to locate the good robot. Photogra- phed at LegoLab, University of Aarhus, Denmark

© VOLKER STEGER/SCIENCE PHOTO LIBRARY