Are the two x's shown in the two different colored boxes different colors? Or are they the same?? It appears that there are two different colored figures but the two x's are actually connected in the middle. Look at where the line crosses the line between the two colors. The two x's turn out to be the same color! This confuses the whole color context issue. How one color close to another can change its appearence.
Look at the image with the deep green on the right and the gray on the left. Above them are two obviously different colored stripes, the lower a brownish-green and the upper a yellowish-orange. The small rectangles look to be the same. Focus your eyes on a spot between the two rectangles. The rectangles happen to correspond with the two stripes previously mentioned. This illusion proves the author's manipulation of color called subtraction of color (how to get rid of too much light or dark in a color). Again, this demonstrates the effects of colors close by, similiar to the first except in this case when the rectangles look the same they are in fact not.
With this image, the illusion is some what apparent. The two walls have different backgrounds, white and black. Do the colors of the bricks look different to you? They, in fact, are not different. The background is what makes them appear to be lighter and darker. The background color can actually manipulate the foreground color.
To create an afterimage from this stimulus, stare at the black dot found in the yellow circles. Your eyes must stay focused on that black dot or the effect will not occur. When 30 seconds have passed, shift your eyes to the white square next to the original stimulus. Focus on the black dot in the center. You should experience a visual containing the opposite of the original. The circles should appear white and the voids (white spaces between the circles) should appear yellow. This is a result of the image being burnt onto your retina when the receptor cells get tired they go into "reverse". Now look at a plain part of the wall and the images of the diamonds should look larger. If they do not, try it again only staring at the original image for a longer period of time. This occurrence is similar to what goes on in a movie theater with the projection of an image. Your eyes are now the projector and the wall is now the screen.
Flashbulb: This afterimage is presented to the retina through a flash of bright light. When the retina has adjusted to the darkness, the figure that is illuminated by the light is burnt onto the retina. When you move your eyes, the image should move as well, as a result of the burning. In order for this procedure to work properly you must be looking in the general direction of your lab assistant.
Black and White: This afterimage is similar to the yellow circles in the way that the eye is effected by it. Due to the direct color contrast of white and black, you see a color that falls in the middle of the two. When you stare at the white dot in the center square and then shift your focus to the black dot you will see little grey dots in the white lines between the grids. Once again the stare should last for thirty seconds or more. The way that the grey dots are always moving emphasizes the point that your eyes are always in motion. This image is another result of the visual receptors getting overloaded.
Isle of Dogs: This image introduces the figure-ground theory. Figure-ground deals with the concept of differentiating between the object of the image and its surroundings. In this illusion one can see either a pair of dogs resting together or two hills. The visual cues presented in this image such as water and other geographical markings influence the subject to see two hills rather than the two dogs resting. However, once the subject realizes the two dogs resting it is difficult for him or her to see anything else. You can only see one or the other at any moment. You cannot see both at the same time.
Camouflage: The opposite to figure-ground is camouflage. Instead of distinguishing between object and background, the two become equally as important. The ability of seeing the image is directly related to how intertwined the background and the foreground really are. In this image the term "WAY" should appear with some effort.
Depth Perception: When perceiving three-dimensional images on a two-dimensional plane depth can be distorted. When the majority of depth cues are consistent with each other and one is not that inconsistent cue becomes forced by the brain to be consistent. That cue is then seen in a distorted fashion. In this image the grids create the appearance of a corridor. Depending on where the human figures are placed the brain perceives them as being either close by or far away. The brain has been conditioned to perceive objects that are far away as smaller but yet all figures are equal in size. So the ones further away look bigger.
Mental Set: Depending on which way the stimulus is read, one would see either a "B" or a "13." This is a result of the mental set which is also the expectations derived from the reading of the stimulus. Life experience manipulates the way this image is perceived. If one first reads and "A" then they will not consider the next to be a "13."
Perceptual Set: The words in the following image have been cut up in various ways. To the extent that one is familiar with these words or the amount of lettering that is left contributes to the ability of the subject to recognize the word. Those toward the bottom tend to be more difficult.
Word Perception: This illusion demonstrates the influence that sound can have over what we see. When people read this paragraph they tend to skip certain appearances of the letter "f." For instance, the word "of" presents the "f" being pronounced as a "v" so it is more likely to be skipped. The word "phenomenon" does not get picked even though it sounds like it starts with the "f" sound. When counting the "f"'s in this paragraph you should total a number of eleven.
Just a Clown?: When looking at this illusion one can see either a clown or the entire circus. What you see depends on the position of your head. When trying to see the entire circus you should tilt your head to the left.