What is Perception?

Definition of Perception:

Very simple definition of Perception is
Sensation + Meaning = Perception

“Give meaning of any things through his sensation is called Perception”.

“Thus perception in humans describes the process whereby sensory stimulation is translated into organized experience.”

Types of Perception:
1- Form perception.
2- Color perception.
3- Perception of Movement.
4- Time Perception.
5- Perception of Space and Depth.

There are many different ways of perceiving the world. One of these ways is by perceptual organization. Perceptual organization are processes used to group basic sensory elements together into perceivable objects. The two basic principles of perceptual organization involves perceiving figures embedded in a perceptual background and organizing what you see, or what you perceive, in the simplest form possible. Another type of perception is depth perception, which is primarily utilized by visual or auditory senses. The organ used for visual perception is the eye. The eye is an extremely complex organ. It is composed of multiple of structures each having it’s own specific function or functions (refer to diagram). The cornea is a clear protective membrane which allows for the passage of light but blocks the entrance of dust. The lens is just behind the cornea and it focuses the light entering into the eye. The light forms an image which falls on the retina. This image is upside down and is processed by the brain. The amount of light entering the eye is controlled by the iris, the colored structure of the eye. The pupil is a black dot in the center of the eye through which light passes. The retina contains over 100 million nerve cells known as rods and cones. Cones are responsible for colored vision and rods are used for black and white vision.

1-Figure Ground Perception:

Suppose ! You can see the figure of rabbit and tree. If you see the tree then rabbit go to the ground and tree called the figure. Suppose that if you see the rabbit then tree go to ground and rabbit called the figure. I hope you understand.

Figure ground perception is the tendency to discriminate between target and background stimuli. The stimulus we perceive as being the target is referred to as the figure. The other stimuli that we do not perceive as the target make up the background, or ground.
The vase seen at right can be perceived in two different ways. If the black is perceived as the background, you will see a vase. However, if you perceive the vase as the background, you will see two faces.

An interesting phenomenon occurs when looking at a square centered over top of several, closely spaced concentric circles. In the figure at left, all of the sides of the square are perfectly straight. Go ahead and check with a straight edge. However, the sides of the square will appear to bend inward toward the center of the circles. This is known as background mediated illusion. The background is responsible for the distortion seen in the figure.

Organization of Perception

The Law of Pragnanz, also known as the Law of Simplicity, states that we tend to perceive the world in the simplest form possible. There are two major parts to this law: closure and grouping. Closure is the tendency to fill in missing portions from a perceptual array, or to fill in the gaps. Grouping occurs when similar or proximal stimuli are perceived as belonging together in a group.

A common example used to illustrate closure is the perception of a complete triangle from three lines. This can be obseved at right. If you look closely you can actually see two triangles in the figure. Grouping can be observed by looking at the collection of black dots below. Your brain groups the dots together.

Depth Perception

Humans perceive depth in a seemingly two dimensional world by interpreting binocular visual cues from the environment. They interpret those stimuli in the brain. Two depth cues that require both eyes are binocular disparity and convergence. Your eyes are separated by a space. This allows them to receive two slightly different images. As distance from your eyes increases the difference between the two images decreases. Binocular disparity is the depth cue that is based on the difference between these two images. Your brain interprets images that are very similar in both eyes as far away, and images that are different in both eyes as closer.

Another way for you brain to interpret the distance to objects is known as convergence. This is when your brain interprets the tension in the muscles that control eye movement. Binocular disparity is used with images that are farther away, perhaps up to 1000 feet. Convergence is used when the object is eighty feet away or closer.

An artistic use of the human processing of depth perception is utilized in stereograms. Have you ever looked at a stereoscopic image, or “magic eye”? They are two dimensional images, but they can be perceived as three dimensional images in brain. The feeling of “depth” that you get by looking at a statue instead of looking at a photo of the same statue, is due to the fact that the human body has two eyes. By having two pictures of the same object, taken by two different positions, which is the case of the human eyes, you can get a “three dimensional image.” In the same way, the eyes forward to the brain two slightly different pictures. It is the brain that must “compute” a 3-D representation of the scene. The brain can make mistakes in this process of designation of pairs! It is these mistakes which make possible the 3-D feeling that we get from viewing a stereogram.
To see some examples of stereograms follow any of the links below.

Size Constancy

Imagine yourself outside looking up at an airplane high in the sky. You lift up your hand and see that the plane is smaller than your finger, yet you still know that the plane is large enough to hold hundreds of people. Due to the information in your memory stores, you are still able to perceive the actual size of the airplane despite a change in the size of the retinal image. This concept is known as size constancy.
Despite the fact that you know images that are far away are actually the same size as if they were closer, your brain can be fooled. An example of this is the moon illusion, in which the moon on the horizon appears larger than one higher in the sky. The moon doesn’t actually changes size, but it’s relationship to the horizon can make it seem larger lower in the sky. This phenomenon can also be explained using the figure below. The center circles are actually both the same size, yet they appear to different because of their relationship to the surrounding circles. Our brain perceives the circle surrounded by larger circles as smaller, because it is smaller in relation to the surrounding circles. The opposite is true for the circle surrounded by smaller circles.

I hope you like my blog which about Perception. I hope you enjoy it.