Is the rabbit hole as deep as you think it is? Perception Is the rabbit hole as deep as you think it is?

Group A You are going to look briefly at a picture and then answer some questions about it. The picture is a rough sketch of a poster for a costume ball. Do not dwell on the picture. Look at it only long enough to “take it all in” once. After this, you will answer YES or NO to a series of questions.

Group B You are going to look briefly at a picture and then answer some questions about it. The picture is a rough sketch of a poster for a trained seal act. Do not dwell on the picture. Look at it only long enough to “take it all in” once. After this, you will answer YES or NO to a series of questions.

Picture

In the picture was there . . A car? A man? A woman? A child? An animal? A whip? A sword? A man’s hat? A ball? A fish?

Conclusion Top Down processing – you go beyond the sensory information to try to make meaning out of ambiguity in your world What you expect (your experiences and your perceptual set) drives this process Today we will see what expectations we all have in common.

The first step in Perception is Attention We sense 11,000,000 bits of information per second. We consciously only process about 40 bits (Wilson 2002). The process by which we attend to these bits is called selective attention Selective Attention can miss things! (Click here)

Inattentional Blindness Daniel Simons and Christopher Chabris (1999) Participants told to count how many times the black jersey team passes the ball 50+% of the participants completely missed the following. . . . Click here Change Blindness (click here)

Perceptual Organization When vision competes with our other senses, vision usually wins – a phenomena called visual capture. How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that the brain creates a coherent perceptual experience that is more than simply the sum of the available sensory information, and it does this in predictable ways OBJECTIVE 3| Describe Gestalt psychology's contribution to our understanding of perception.

How do we perceive forms? 1. We organize the visual field into objects (figures) that stand out from their surroundings (ground). OBJECTIVE 4| Explain the figure-ground relationship and identify principles of perceptual grouping in form perception. How good are you at this? And what does that say about you?

How do we perceive forms? 2. After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using GROUPING rules. Closure

It doesn’t always work. Although grouping principles usually help us construct reality, they may occasionally lead us astray.

CLOSURE

What happens when there aren’t enough clues? Ambiguous figures – proof of perception You can’t hold two different perceptions at the same time.

Apply what you’ve learned Take the worksheet in you quads and apply what we have done today to each of the figures Tell me why we perceive the world as we do.

How do we perceive forms? Perceptual Constancy Our tendency to perceive objects as stable and unchanging despite changing sensory information Size constancy Shape constancy Color constancy

Depth Perception Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. OBJECTIVE 5| Explain the importance of depth perception, and discuss the contribution of visual cliff research to our understanding of this ability. Innervisions Visual Cliff

Binocular Cues Retinal disparity: Images from the two eyes differ. While focusing far away try touching your fingers about 5 inches directly in front of your eyes. You will see a “finger sausage” The amount of disparity (difference) between the two images can be used as a cue for distance Try holding up two fingers one in front of the other. Focus on the front one (you should now see two images of the back one). Now move the back one away from, then back towards you, whil still focusing on the front one.

Binocular Cues Convergence: Neuromuscular cues. When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects. OBJECTIVE 6| Describe two binocular cues for perceiving depth, and explain how they help the brain to compute distance.

Monocular Cues Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away. OBJECTIVE 7| Explain how monocular cues differ from binocular cues, and describe several monocular cues for perceiving depth.

Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer.

Monocular Cues Relative Clarity: Because light from distant objects passes through more light than closer objects, we perceive hazy objects to be farther away than those objects that appear sharp and clear.

Monocular Cues Texture Gradient: Closer objects tend to have a courser texture than to far way objects © Eric Lessing/ Art Resource, NY

Monocular Cues Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. © The New Yorker Collection, 2002, Jack Ziegler from cartoonbank.com. All rights reserved.

Monocular Cues Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the ones that are shaded on top are seen as “sticking out toward us” From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved.

Perception of Movement Apparent movement Illusion that still objects are moving Autokinetic illusion Perceived motion of a single object due to eye movements on an ‘impoverished background’ Stroboscopic motion Created by a rapid series of still pictures Phi phenomenon Apparent motion created by lights flashing in sequence