To find out about some of the phenomena of perception, psychologists often study situations that pose problems in making sense of our sensations.
What do you learn about your own perception by trying to identify the object staring at you from this photo? Source: From Dallenbach, K. M. (1951). A puzzle-picture with a new principle of concealment. American Journal of Psychology.
Consider, for example, the image displayed above. To most people, the figure initially looks like a blur of meaningless shadings. A recognizable creature is staring them in the face, but they may not see it. When people finally realize what is in the figure, they rightfully feel “cowed.” The figure of the cow is hidden within the continuous gradations of shading that constitute the picture. Before you recognized the figure as a cow, you correctly sensed all aspects of the figure. But you had not yet organized those sensations to form a mental percept—that is, a mental representation of a stimulus that is perceived. Without such a percept of the cow, you could not meaningfully grasp what you previously had sensed.
The preceding examples show that sometimes we cannot perceive what does exist.
So, sometimes we perceive what is not there.
Other times, we do not perceive what is there.
And at still other times, we perceive what cannot be there.
The existence of perceptual illusions suggests that what we sense (in our sensory organs) is not necessarily what we perceive (in our minds). Our minds must be taking the available sensory information and manipulating that information somehow to create mental representations of objects, properties, and spatial relationships within our environments (Peterson, 1999).
The way we represent these objects will depend in part on our viewpoint in perceiving the objects.