Chapter 5 Perceiving the World

Some Key Terms Perception: How we assemble sensations into meaningful patterns Bottom-up processing: Analyzing information starting at the bottom (small units) and going upward to form a complete perception Top-down processing: Pre-existing knowledge that is used to rapidly organize features into a meaningful whole

Selective Attention Giving priority to a particular incoming message. Dividing Attention: Allotting mental space or effort to various tasks or parts of a task

Perceptual Expectancies Perceptual expectancy (set): Past experiences, motives, contexts, or suggestions that prepare us to perceive in a certain way

Attention and Perception Inattentional blindness: Failure to perceive a stimulus that is in plain view, but not the focus of attention Orientation response: Bodily changes that prepare an organism to receive information from a particular stimulus

Perceptual Grouping Figure–ground organization: Inborn; part of a stimulus stands out as an object (figure) against a plainer background (ground) Reversible gigure: Figure and ground that can be reversed

A challenging example of perceptual organization A challenging example of perceptual organization. Once the camouflaged insect (known as a giant walking stick) becomes visible, it is almost impossible to view the picture again without seeing the insect. Fig. 5-6, p. 156

Gestalt Principles of Organization Nearness: Stimuli that are near each other tend to be grouped together Similarity: Stimuli that are similar in size, shape, color, or form tend to be grouped together Continuation, or continuity: Perceptions tend toward simplicity and continuity

Gestalt Principles of Organization (cont) Closure: Tendency to complete a figure so that it has a consistent overall form Contiguity: Nearness in time and space; perception that one thing has caused another Common region: Stimuli that are found within a common area tend to be seen as a group

More on Perception Size constancy: Perceived size of an object remains constant, despite changes in its retinal image size Native perception: A perceptual experience based on innate processes

Convergence For a simple illustration of convergence, have students focus on a distant point and then bring a finger up into the line of sight. The finger will appear “transparent” because the line of sight is nearly parallel. If students then look directly at the finger, it will once again become “solid” (convergence). A variation on this (which also illustrates retinal disparity and fusion) involves again fixating on a distant point. This time the tips of the index fingers of both hands should be brought together in the line of sight, about twelve inches from the eyes. Students should see a small “sausage” forming and disappearing between their fingertips as the two retinal images overlap.

(a) Linear perspective. (b) Relative size. (c) Light and shadow (a) Linear perspective. (b) Relative size. (c) Light and shadow. (d) Overlap. (e) Texture gradients. Drawings in the top row show fairly “pure” examples of each of the pictorial depth cues. In the bottom row, the pictorial depth cues are used to assemble a more realistic scene. Fig. 5-15, p. 162

Some More Key Terms Empirical perception: A perception strongly influenced by prior experience Shape constancy: The perceived shape of an object is unaffected by changes in its retinal image Brightness constancy: Apparent brightness of an object stays the same under changing lighting conditions

What do you see in this painting? This painting by abstract artist Al Held is 9 feet by 9 feet. If you process the painting “bottom-up,” all you will see is two small dark geometric shapes. Would you like to try some top-down processing? Knowing the painting’s title will allow you to apply your knowledge and see the painting in an entirely different way. The title? It’s The Big N. Can you see it now? Figure 5.1 Fig. 5-1, p. 151

Depth Perception Definition: Ability to see three-dimensional space and to accurately judge distances Visual cliff: Apparatus that looks like the edge of an elevated platform or cliff on one side and a tabletop on the other

Depth Depth cues: Features of the environment, and messages from the body, that supply information about distance and space Binocular depth cue: Depth cue that can be sensed with two eyes Monocular depth cue: Depth cue that can be sensed with one eye

Muscular Cues for Depth Perception Retinal disparity: Discrepancy in the images that reach the right and left eyes Stereotopic vision: Three-dimensional sight; perception of space and depth caused by the fact that the eye receives different images

Relative Motion (Motion Parallax) Nearby objects move a lot as your head moves; distant objects move slightly People are more likely to say trucks are moving faster than cars because they are bigger

Figure 5.16 • Figure 5.21. On a dry lake bed, relative size is just about the only depth cue available for judging the camera’s distance from this vintage aircraft. What do you estimate the distance to be? For the answer, look ahead to Fig. 5-16, p. 163

Figure 5.21 Before you can use familiar size to judge distance, objects must actually be the size you assume they are. Either these men are giants, or the model airplane was closer than you may have thought when you looked at • Figure 5.16. Fig. 5-21, p. 165

Some Illusions Moon illusion: Apparent change in size that occurs as the moon moves from the horizon (large moon) to overhead (small moon) Apparent-distance hypothesis: Horizon seems more distant than the night sky

Figure 5.8 (a) An impossible figure — the “three-pronged widget.” Fig. 5-8a, p. 156

Figure 5.8 (b) It might seem that including more information in a drawing would make perceptual conflicts impossible. However, Japanese artist Shigeo Fukuda has shown otherwise. (“Disappearing Column” © Shigeo Fukuda, 1985.) Fig. 5-8b, p. 156

Figure 5.29 Some interesting perceptual illusions. Such illusions are a normal part of visual perception. Fig. 5-29, p. 170

Figure 5.20 The Ponzo illusion may help you understand the moon illusion. Picture the two white bars as resting on the railroad tracks. In the drawing, the upper bar is the same length as the lower bar. However, because the upper bar appears to be farther away than the lower bar, we perceive it as longer. The same logic applies to the moon illusion. Fig. 5-20, p. 165

Perceptual Habits Ingrained patterns of organization and attention Other-race effect: Tendency to be better at recognizing faces from one’s own racial group than faces from other racial or ethnic groups Active movement: Self-generated action; accelerates perceptual adaptation Korean Monks

Perceptual Comparisons 4 volunteers are going to guess my height and weight They leave the classroom Two more volunteers stand on either side of me for each person guessing Rest of class, write down their guesses Did the guesses change based on who was around me?

Context Context: Information surrounding a stimulus; affects perception Frames of reference: Internal standards for judging stimuli

Figure 5.24 The Ames room. From the front, the room looks normal; actually, the right-hand corner is very short, and the left-hand corner is very tall. In addition, the left side of the room slants away from viewers. The diagram shows the shape of the room and reveals why people appear to get bigger as they cross the room toward the nearer, shorter right corner. Fig. 5-24a, p. 166

Illusions: Is What You See What You Get? Illusion: Length, position, motion, curvature, or direction is constantly misjudged Hallucination: When people perceive objects or events that have no basis in external reality Stroboscopic movement: Illusory motion perceived when objects are shown in rapidly changing positions

Müller-Lyer Illusion Two equal-length lines tipped with inward or outward pointing V’s appear to be of different length; based on experience with edges and corners of rooms and buildings

Extrasensory Perception (ESP) Purported ability to perceive events in ways that cannot be explained by known capacities of sensory organs Parapschology: Study of ESP and other psi phenomena (events that seem to defy accepted scientific laws)

Parapsychological “Abilities” Clairvoyance: Purported ability to perceive events at a distance or through physical barriers Telepathy: Purported ability to read minds Precognition: Purported ability to accurately predict the future Psychokinesis (mind over matter): Purported ability to influence inanimate objects by willpower

More ESP Terms Zener cards: Deck of 25 cards, each having one of five symbols Run of luck: Statistically unusual outcome that could occur by chance alone (e.g., getting five heads in a row, two jackpots within six pulls of a slot machine)

Throughout your lecture, I made a small but novel gesture every few minutes. The gesture should be something that would draw little attention if done once. Did you become aware of the gesture as it was repeated? Or were you used to it? Discuss their perceptions near the end of the session.

Stroop Effect Handouts