Where is it going? Motion Perception

Motion Perception Neural pathways in the brain combine information about eye-muscle activity, the changing retinal image, and the contrast of the moving object to the stationary background. Brain views larger objects as moving more slowly than smaller objects Brain assumes shrinking objects are retreating and enlarging objects are approaching

Stroboscopic Motion The illusion of motion by the rapid projection of slightly changing images The concept a motion picture (movie) uses

Phi Phenomenon The illusion of motion when fixed lights are turned on and off in a sequence To see how this works click below: Stare at the X in the middle and notice what happens. Is the Green Dot Moving? Lilac Chaser Illusion OR goto http://www.weeville.com/eyetest.htm Want to know more about this? Click here to find out.

Induced Motion Karl Duncker studied this with the dot and moving rectangle. Rectangle moved but people thought it was the dot moving. This because of top-down processing (people expected the dot to move) and our assumption that the background is stationary.

Induced Motion Demo Click below to view video The “Flying” Airplane The plane is stationary, the background is what is moving. Check out more Induced Motion at the link below: Induced Motion

Spiral Motion Detectors Research shows that different neural pathways in the cerebral cortex process information about the depth of objects, movement, form, and color. As you view the spiral motion your spiral motion receptors are being used. When you look at a stationary object, they are still on for a brief instant causing the illusion.

Spiral Motion Check it out by clicking on video below: Spiral Motion & Buddha Stare without blinking at the center of the spiral. To view an even better spiral motion demo click on : Spiral Motion Detectors Demo

Click on the link to view: Motion Blindness Look steadily at one stationary point, such as one of the white discs. Don’t blink as blinks and sudden eye movements destroy the illusion. Notice that one, two or all of the white discs will disappear and reappear. Deals with your selective attention Click on the link to view: Motion Blindness Demo

Perceptual Constancy

Perceptual Constancy Perceiving objects as stable or constant (having consistent lightness, color, shape, and size) even as illumination and retinal images change Example: as a person walks away from you their retinal image decreases in size Example: A car in the distance is still known to be the same color and size as it was when it was driving past you. Important function of the perceptual system is to represent constancy in our environment even when the retinal image varies

Perceptual Constancy: Size Constancy

Size Constancy A person’s understanding that as an object moves further or closer to them its actual size stays the same As an object appears to become larger we realize it is getting closer, not bigger. As an object appears to become smaller we realize it is moving farther away, not getting smaller. Perceptions of the world depend on our experience - Colin Turnbull’s experiment with Kenge

Relationship Between Perceived Size and Perceived Depth To perceive the size of objects accurately we must also perceive their distance accurately Thus, many visual illusions occur simply because a particular image lacks sufficient depth cues Retina Pupil Image A B Hockenbury powerpoint (Schulman) Key point here: The retinal image is the same for the near and distant objects. For this to happen the distant object must be larger. This figure shows that image size depends upon both object size and distance

Size Constancy People are the same size even though their image sizes differ The depth cues such as linear perspective and relative size help the visual system judge the size accurately Hockenbury powerpoint (Schulman)

Size Distance Relationship

Size Distance Relationship

Size Distance Relationship

Perceptual Constancy: Shape Constancy

Shape Constancy The understanding that an object’s shape remains the same even though the angle of view makes the shape appear changed

Shape Constancy It is hard to tell if the figure on the upper right is a trapezoid or a square slanted backward. If we add texture, the texture gradient helps us see that it is actually a square Hockenbury powerpoint (Schulman)

Perceptual Constancy: Lightness Constancy

Light (Brightness) Constancy The ability to see an object as having a constant level of brightness no matter how the lighting conditions change If you look at a sheet of paper in bright sunlight it looks blazingly white. View the same sheet in a dimly lit room, and it appears gray. Has the paper changed? Of course not! We know the paper stays “white” no matter what the lighting conditions are.

Brightness Contrast Perceived lightness stays roughly constant as long as the context or surroundings stay the same. When the context changes you may perceive the color as changing. Although the interior squares are in fact identical, we perceive the one as lighter or darker because of the contrast with its surroundings. Want to see more of these perceptions? Goto http://www.skidmore.edu/~hfoley/Perc4.htm#lightcon

Brightness Constancy: Example Obviously A is a dark square in light and B is a light square in shadow, right? Both A and B are identical shades of gray! Can you believe that they are sending the identical level of light energy to your retina? The organization of the scene into lighted areas and shadowed areas must play a role in determining the perceived lightness of the squares. The white square (Square B) is reflecting so little light that it is reflecting the same amount of light as a black square in direct light (Square A).

Illusion of the Camera Play “Lights, Camera, Magic!” (12:53) Segment #10 from Scientific American Frontiers: Video Collection for Introductory Psychology (2nd edition).

Perceptual Interpretation To what extent do we learn to perceive? If our eyes were covered with blinders during our early years, would we enjoy normal perception if they were later removed? The adaptation goggles show us that our brain can adapt to changes that occur later in life.

Sensory Deprivation & Restored Vision Early visual experience can have a profound effect on perception. Blakemore & Cooper’s restricted environment with kittens. Do the kittens ever fully regain normal sensitivity to horizontal or vertical lines? NO. The “Use it or lose it” phenomenon. From the time their eyes first opened, and until the age of 5 months, these kittens were removed from darkness each day to spend 5 hours alone in a black-and-white striped cylinder with a clear glass floor. A stiff collar prevented the kittens from seeing anything else, even their own bodies. Afterward, these kittens had difficulty perceiving horizontal forms, compared with other kittens exposed only to horizontal forms.

Sensory Deprivation & Restored Vision These experiments show that lacking stimulation, the cortical cells had not developed normal connections making them functionally blind to shape. A sensory restriction does no permanent damage if it occurs later in life. This suggests that visual experiences during infancy are a critical period for normal sensory and perceptual development. Experience guides the organization of the brain’s neural connections. If deafness or blindness is corrected as an infant, it awakens the pertinent brain area. Nurture sculpts what nature has endowed.

Perceptual Set

Perceptual Set A mental predisposition to perceive something one way and not another If we believe we are going to see or hear something, we often do Example of top-down processing Influence of the “power of suggestion” (subliminal perception) Guided by schemas: concepts or mental frameworks that organize and interpret information

Schemas Children’s drawings reflect their schemas of reality, as well as their abilities to represent what they see. This drawing by 4-year-old Anna illustrates that the face has far greater importance than the body in young children’s schemas of essential human characteristics.

Face Schemas Which is the real Margaret Thatcher? We don’t have a schema for upside down faces. As it rotates you’ll find out when you cannot assimilate her mouth and eyes to into your schema for faces Click to below to view: The Thatcher Illusion

Perceptual Set The influence of prior assumptions and expectations on perceptual interpretations

Perceptual Set What do you see in the center picture: a male saxophonist or a woman’s face? Glancing first at one of the two unambiguous versions of the picture is likely to influence your interpretation.

Subliminal Perception Play “Studying the Effects of Subliminal Stimulation on the Mind” (4:46) Segment #9 from The Mind: Psychology Teaching Modules (2nd edition).

Context The setting or environment in which we interpret sensory stimuli Culture can also influence how we perceive information. Nativist Position – people throughout the world view the world the same way because they share the same biological perceptual rules. Empiricist Position – People actively construct their perceptions by drawing on their prior learning and cultural experiences. Carpentered-World Hypothesis – People living in urban and industrialized environments where there are more right angles and straight lines will be more susceptible to the Muller-Lyer Illusion than people in non-carpentered natural environments.

Context & Culture What is above the woman’s head? In one study, nearly all the East Africans who were questioned said the woman was balancing a metal box or can on her head and that the family was sitting under a tree. Westerners, for whom corners and boxlike architecture are more common, were more likely to perceive the family as being indoors, with the woman sitting under a window.

Context Effects The magician’s cabinet: Is the box in the far left frame lying on the floor or hanging from the ceiling? What about the one on the far right? In each case, the context defined by the inquisitive rabbits guides our perceptions.

Illusions

Illusions When we misperceive the true characteristics of an object or image. Help researchers understand how sensation and perception normally works

Müller-Lyer Illusion Perceptual psychologists have hypothesized that the top horizontal line looks longer because it also looks farther away Specifically, the inward pointing arrows signify that the horizontal line is closest to you, and the outward pointing arrows signify the opposite case Hockenbury powerpoint (Schulman)

Müller-Lyer Illusion

Müller-Lyer Illusion Most people think segment AB equals BC. In reality AB is much longer than BC.

Müller-Lyer Illusion

Müller-Lyer Illusion

Müller-Lyer Illusion

Müller-Lyer Illusion: Click below to view a video of how this works: Muller-Lyer Illusion Explanation

Ponzo Illusion Converging lines indicate that top line is farther away than bottom line Hockenbury powerpoint (Schulman)

The interplay between perceived size and distance (a) The monocular cues for distance make the pursuing monster look larger than the pursued. It isn’t. (b) This visual trick, called the Ponzo illusion, is based on the same principle as the fleeing monsters. The two red bars cast identical-sized images on our retinas. But experience tells us that a more distant object can create the same-sized image as a nearer one only if it is actually larger. As a result, we perceive the bar that seems farther away as larger.

Click Below to View an Explanation: Moon Illusion Moon appears larger when it is on the horizon than when it is directly overhead. Objects on the horizon are perceived as farther away than those above us The moon appears to be behind those objects on the horizon. Since it is bigger than those object it is perceived as huge! (click on box below for explanation) Click Below to View an Explanation: Moon Illusion

Ames Room Illusion: Secret Revealed We perceive the room to be as we are used to, a perfect square or rectangular. When in fact it is a trapezoid!

Poggendorff Illusion

See how this and others like it are done Impossible Figures These grouping principles help us construct reality but perceptual contradictions can lead us astray See how this and others like it are done

More Impossible Figures

More Impossible Figures

Escher’s Impossible Scenes

Chrysanthemum Is this 3-D?

Toying with your Perception Want to see more Optical Illusions? Optical Illusion Montage 1 Optical Illusion Montage 2 Contrast Asynchrony Illusion Contrast Asynchrony illusion

Water or Monks? Heads or Houses?

Rocks or Horses? In or out of the picture?

Ghost Perceptions? Watch the car commercial closely. What perceptual concept causes you to see the faint image of the “ghost?” Click Below to view: Ghostly Car Ad