In the previous videos, we've looked at how we perceive color, shape, and depth. Next, we'll address the question of how we're able to perceive motion. When you see the image currently displayed on your screen, do you perceive any movement in the circles?
Within the brain, there are specific areas responsible for detecting movement, implying that humans have specialized motion detectors. However, In addition to being able to visually perceive real movements, we are also able to perceive illusionary movements or apparent movement, which is defined as the perception that a stationary object is moving. And this is why you may have perceived movement within the image shown in the previous slide.
Apparent movement is what happens when you watch an IMAX movie and feel as if you're moving when you're actually not. Or sometimes you may be sitting in a parked car and feel as if your car is moving when it's actually the car beside you that's moving. These are all examples of apparent movement, and psychologists are equally interested in real movements and apparent movements.
Here's another example of apparent movement. If you see some type of movement in this stationary picture, then you're experiencing apparent movement. There's also one more element in the perception of visual stimuli, that makes it easier for us to interpret the objects we see around us, which is the perceptual constancy of an object. Even with the ever-changing world around us, we recognize that objects do not physically change despite how their retinal images or how the objects appear in our retina change. There are three types of perceptual constancies which allow us to perceive the size, shape, and color of objects as being constant.
Size constancy allows you to determine that an object remains the same size even though the retinal image of the object may change in size. In this picture, you can see that the person standing by the column is still the same size even when he moves to stand next to the column farther away from you. Because size constancy tells you that the person is still the same person, and thus the same size, no matter how much he moves away from you.
You can experience the same phenomenon when you see a car move away from you. As the car travels farther and farther, then the car would appear smaller and smaller. Yet in your mind, you do not believe that the car is shrinking owing to size constancy. Shape constancy, on the other hand, allows you to recognize that an object is still the same shape even when its orientation changes.
I'm sure you'd agree that the first, second, and third, and fourth images all depict a door. If you pay close attention to the shape of the green door, you'll see that the door in the first image is rectangular, while the door in the third image is a trapezoid. Yet, despite its changing shape, you would still say that a door is rectangular in shape. This is due to your ability to perceive shape constancy. As with the previous image, your ability to perceive a coin as circular, no matter how much you twist and turn the coin, is also thanks to shape constancy.
Lastly, color constancy allows you to perceive an object as having the same color even with changes in the lighting of the environment. If I ask you what color a banana is, you'd probably say yellow. If I then ask you the color of a banana that is hidden in a backpack, you'd still say that the banana is yellow. What if I now store the banana in a dark storage room? Is it still yellow?
Sure. What if I place the banana in a room with... pink fluorescent lighting. Is the banana still yellow then?
Of course. Your ability to perceive a banana as yellow, despite changes in the lighting of the environment where the banana is kept, demonstrates your color constancy ability. In this picture, we see both square A and the square pointed by the red arrow as black.
even though in reality, if you compare the two squares, you'll realize that square A is much lighter in color. Similarly, we see square B and the square pointed by the purple arrow as white, even though square B is much darker in color. This, once again, demonstrates color constancy. You should remember that perception involves interpreting and attaching meaning to a sensory stimulus received by the sensory receptors. Because we have to interpret sensations into meaningful perception, sometimes we may end up being fooled by our own senses, as you've demonstrated yourself in some of the previous examples provided.
This is especially true in the case of our eyes. When you're fooled by your own eyes, you are said to be experiencing perceptual illusions. For examples on the different kinds of perceptual illusions that may occur, please search for this group of pictures in your textbook and read the information that comes along with each picture. You can try to compare what you perceive from the images with what the physical images actually illustrate.
The following are several examples of perceptual illusions. The first is the Müller-Lyer illusion. A German psychologist by the name of Franz Karl Müller-Lyer in the year 1889 discovered this illusion.
The illusion shows that a line of the same length can be perceived differently as a result of the addition of either inward facing angles or outward facing ones at the ends of the line. In daily life, We experience this illusion when we perceive the vertical line in the corner of a room as being taller when we look at it from the inside of the room than when we look at the same line from the outside of the room. The second illusion is the vertical horizontal illusion.
We tend to perceive a vertical line as longer than a horizontal line even when they're both the exact same length. The Ames Room Illusion was invented by Adalbert Ames Jr. in the year 1946. The illusion demonstrates the application of the gestalt principle of relative size, in which our perception of the size of a person may be distorted in such a way that creates an optical illusion. If we look at this picture, the person who should be tallest looks the shortest, while the child who should be the shortest looks the tallest. This illusion occurs because when we look at the room from a hole in one of the walls, we are forced to look at the inside of the room using one eye only, therefore distorting the perception of depth that would have normally resulted from binocular cues, or from using both eyes to view the room. As a consequence, we are unable to determine that the wall inside the room is actually built diagonally, and the floor is slanted.
The illusion also shows that despite conflicting visual information, a person viewing the room tends to believe in their own expectation that a room should be cubical and thus ends up ignoring the possibility that it's the room that is shaped oddly, while readily accepting that it is the people inside the room that change in size. The next illusion is the Ponzo illusion which was invented by Mario Ponzo, an Italian psychologist. in the year 1913. The ponzo illusion demonstrates how the human mind judges the size of an object based on contextual and background cues. Here we can see that two horizontal lines of the same length can be perceived differently as a result of the addition of two lines that suggest linear perspective. A similar phenomenon occurs when we perceive the horizontal lines in a chain track.
The Zollner illusion shows that when there is a pattern that overlaps parallel lines, the pattern would cause us to perceive the parallel lines as misaligned. The following are some other examples of the Zollner illusion. In addition to static visual illusions that we just saw, there are two other illusions of movement, or apparent movements, that we tend to perceive.
One of them is beta movement, which is an apparent movement that occurs when a number of images that are actually separate are presented in quick succession one after another. Due to this quick sequential presentation, we perceive them as one continuous movement. Beta movement is responsible for our perception of animated films as a movement, wherein the quick succession of individual images creates the illusion of an uninterrupted motion.
The next apparent movement is phi-phenomenon, which is what happens when we see the lights on a Christmas tree is moving, even though it's simply due to the lights turning on and off one after another. This is because when we perceive visual images appearing close together in space and time, we tend to infer virtual movement from them. You can learn more about perceptual or optical illusions from the YouTube links provided to you by your course instructor. Based on what you've learned in this video, you should now comprehend that what we perceive is a result of our own interpretation of the visual stimuli detected by our sense organs. And this interpretation is not always consistent with reality.
Things like experiences and expectations play an important role in our perception of our immediate surrounding. Even stationary objects can sometimes be perceived as moving. Distant objects can seem as though they're near.
This shows that contextual information surrounding a particular stimulus can result in a distorted perception of the stimulus.