角度、方向的錯覺( illusions of angle and direction )

圖二稱為波根多夫（Poggendorff）錯覺，即圖中斜線看來像是兩條平行線，但事實上它們是一條直線被分隔開來。
The Poggendorff illusion figure (1860).   http://www.michaelbach.de/ot/ang_poggendorff/index.html

Which of four nail points at the bottom of the board go with the head at the top? You probably think that it is the most left one.

However, the correct answer is the second one from the left. Of course, this illusion also occurs when a rectangle and lines are used instead of a board and nails. This illusion is most profound when the angle between the board and the nails (or the rectangle and the lines) is 30 -45°. It is believed that this illusion is caused by overestimation of the angle as in the Zollner, Hering, and Orbison illusions. On the other hand, the Poggendorff illusion disappears when the angle between the board and nails (or the rectangle and the lines) is 90°. This is probably because we can accurately judge near-vertical and near-horizontal orientations. This is also true for other illusions.

彎曲圖形(illusions of straightness and curvature)

Do the horizontal lines below look straight or curved

Café Wall Illusion

The café wall illusion, sometimes also called the Münsterberg illusion (Ashton Raggatt McDougall 2006), is an optical illusion produced by a black and white rectangular tessellation when the tiles are shifted in a zigzag pattern, as illustrated above. While the pattern seems to diverge towards the upper and lower right corners in the upper figure, the gray lines are actually parallel. Interestingly, the illusion greatly diminishes if black lines are used instead of gray.
The illusion disappears when the position of tiles are not shifted or shifted by the whole size of the squares. These properties are somewhat similar to those of the Fraser illusion.


它的技巧，是在方格邊緣都鑲上了跟平行線一樣色澤比較淡的線條，我們的大腦就隨著直排線上格子的進進出出將水平線給zigzag啦！！！----當橫線間的距離越大或顏色對比減少時，這種錯覺就會減少嘍！
http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/cafe_wall.html  這裡有個連結可以去玩玩看



The original of the Café Wall, St Michael?s Hill, Bristol.
Gregory and Heard (1979) first noticed theillusion on the wall decoration of a café in Bristol, England. The caféwall illusion is only one among many visual distortion effectsinvolving parallel lines. The most famous example of this kind is Zöllner\'s illusion.


The image above shows a picture of a building in Melbourne, Australia designed to exhibit this illusion (C. L. Taylor, pers. comm., Aug. 5, 2006). The building, completed in 2006, is part of Melbourne\'s Digital Harbour Port 1010 and houses the Australian Customs Service (Ashton Raggatt McDougall 2006).