Motion Perception
• Motion simply means the relative/ progressive change in the position of the person in space with
time. Objects cannot be perceived fully when in motion. It is also difficult due to the fact that our
eyes cannot follow the moving object with great precision and efficiency all the time.
Relative Motion
• While looking at moving automobiles, the ones that are nearer seem to be moving more rapidly than those at a moderate distance, and those that are more distant seem to be moving along.
• Relative motion can also be interpreted through experience, when one can fairly tell the speed of a train or a bus by noticing outside the window asto how rapidly the nearby objects are passing.
Radical Motion
• A movement directly towards or away from the observer. Continuous and radical motion is being perceived when the retinal image continuously changes.
• The change in size of the retinal image gives the perception of motion.
Perceptual Constancy
• A perceptual tendency to perceive object as unchanging in size, shape, color, lightness etc., even though
changes in illumination and retinal image do take place.
There are a number of consistencies identified by psychologists
I. Lightness Constancy: Means that the object’s lightness or brightness remains the same in
spite of changes in illumination.
Lightness constancy illustrates an important perceptual principle: Perception is relative. Lightness constancy may occur because the white piece of paper reflects more light than any of the other objects in the room—regardless of the different lighting conditions. Another explanation, proposed by 19thcentury German physiologist Hermann von Helmholtz, is that we unconsciously take the lighting of the room into consideration when judging the lightness of objects.
II .Color Constancy: Closely related with lightness constancy and refers to the perception of color of
the object remaining the same in spite of changes in lighting conditions.
Color constancy can be seen if one has worn a pair of sunglasses with colored lenses. In spite of the fact that the colored lenses change the color of light reaching your retina, you still perceive white objects as white and red objects as red. The explanations for color constancy parallel those for lightness constancy. One proposed explanation is that because the lenses tint everything with the same color, we unconsciously “subtract” that color from the scene, leaving the original colors.
III. Shape Constancy: Means the shape of the object remains the same in spite of some changes in its
orientation.
To understand shape constancy, hold a book in front of your face so that you are looking directly at the cover. The rectangular nature of the book should be very clear. Now, rotate the book away from you so that the bottom edge of the cover is much closer to you than the top edge. The image of the book on your retina will now be quite different. In fact, the image will now be trapezoidal, with the bottom edge of the book larger on your retina than the top edge. (Try to see the trapezoid by closing one eye and imagining the cover as a two-dimensional shape.) In spite of this trapezoidal retinal image, you will continue to see the book as rectangular. In large measure, shape constancy occurs because your visual system takes depth into consideration.
IV. Size Constancy: refers to our ability or tendency to perceive objects as remaining of the same size
despite having distance from the observer.
When an object is near to us, its image on the retina is large. When that same object is far away, its image on the retina is small. In spite of the changes in the size of the retinal image, we perceive the object as of the same size. For example, when you see a person at a great distance from you, you do not perceive that person as very small. Instead, you think that the person is of normal size and far away. Similarly, when we view a skyscraper from far away, its image on our retina is very small—yet we perceive the building as very large.
Visual Illusion
• Also known as optical illusion.
Illusion is misperception, or false perception.
• It is when the physical stimulus constantly and persistently produces error in perception.
• There are various types of illusion of which the most famous are as follows;
i.Muller- Lyer Illusion
The visual illusion in which the two lines of the same lengths appear different because of the change in
position of arrows at each end of two lines__ arrows pointing out appear shorter than the arrows
pointing inwards.
Causes of Illusions
time. Objects cannot be perceived fully when in motion. It is also difficult due to the fact that our
eyes cannot follow the moving object with great precision and efficiency all the time.
Relative Motion
• While looking at moving automobiles, the ones that are nearer seem to be moving more rapidly than those at a moderate distance, and those that are more distant seem to be moving along.
• Relative motion can also be interpreted through experience, when one can fairly tell the speed of a train or a bus by noticing outside the window asto how rapidly the nearby objects are passing.
Radical Motion
• A movement directly towards or away from the observer. Continuous and radical motion is being perceived when the retinal image continuously changes.
• The change in size of the retinal image gives the perception of motion.
Perceptual Constancy
• A perceptual tendency to perceive object as unchanging in size, shape, color, lightness etc., even though
changes in illumination and retinal image do take place.
There are a number of consistencies identified by psychologists
I. Lightness Constancy: Means that the object’s lightness or brightness remains the same in
spite of changes in illumination.
Lightness constancy illustrates an important perceptual principle: Perception is relative. Lightness constancy may occur because the white piece of paper reflects more light than any of the other objects in the room—regardless of the different lighting conditions. Another explanation, proposed by 19thcentury German physiologist Hermann von Helmholtz, is that we unconsciously take the lighting of the room into consideration when judging the lightness of objects.
II .Color Constancy: Closely related with lightness constancy and refers to the perception of color of
the object remaining the same in spite of changes in lighting conditions.
Color constancy can be seen if one has worn a pair of sunglasses with colored lenses. In spite of the fact that the colored lenses change the color of light reaching your retina, you still perceive white objects as white and red objects as red. The explanations for color constancy parallel those for lightness constancy. One proposed explanation is that because the lenses tint everything with the same color, we unconsciously “subtract” that color from the scene, leaving the original colors.
III. Shape Constancy: Means the shape of the object remains the same in spite of some changes in its
orientation.
To understand shape constancy, hold a book in front of your face so that you are looking directly at the cover. The rectangular nature of the book should be very clear. Now, rotate the book away from you so that the bottom edge of the cover is much closer to you than the top edge. The image of the book on your retina will now be quite different. In fact, the image will now be trapezoidal, with the bottom edge of the book larger on your retina than the top edge. (Try to see the trapezoid by closing one eye and imagining the cover as a two-dimensional shape.) In spite of this trapezoidal retinal image, you will continue to see the book as rectangular. In large measure, shape constancy occurs because your visual system takes depth into consideration.
IV. Size Constancy: refers to our ability or tendency to perceive objects as remaining of the same size
despite having distance from the observer.
When an object is near to us, its image on the retina is large. When that same object is far away, its image on the retina is small. In spite of the changes in the size of the retinal image, we perceive the object as of the same size. For example, when you see a person at a great distance from you, you do not perceive that person as very small. Instead, you think that the person is of normal size and far away. Similarly, when we view a skyscraper from far away, its image on our retina is very small—yet we perceive the building as very large.
Visual Illusion
• Also known as optical illusion.
Illusion is misperception, or false perception.
• It is when the physical stimulus constantly and persistently produces error in perception.
• There are various types of illusion of which the most famous are as follows;
i.Muller- Lyer Illusion
The visual illusion in which the two lines of the same lengths appear different because of the change in
position of arrows at each end of two lines__ arrows pointing out appear shorter than the arrows
pointing inwards.
Causes of Illusions
- Sensory deficits and defects
- Readiness and expectation
- Atmospheric variables
- Effect of drugs
- Artistic manipulation
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