PSYCHOLOGY from inquiry to understanding CHAPTER THIRD EDITION Copyright © 2014, © 2011, © 2009 by Pearson Education, Inc. All Rights Reserved Sensation.

PSYCHOLOGYPSYCHOLOGYfrom inquiry to understanding

CHAPTER

THIRD EDITION

Copyright © 2014, © 2011, © 2009 by Pearson Education, Inc.All Rights Reserved

Sensation and PerceptionHOW WE SENSE AND CONCEPTUALIZE THE WORLD

4

Slides prepared by Matthew Isaak

Understanding Psychology: from Inquiry to Understanding, Third EditionLilienfeld | Lynn | Namy | Woolf

Learning Objectives

LO 4.1 Identify the basic principles that apply to all senses.

LO 4.2 Discuss the role of attention and the nature of the binding problem.

LO 4.3 Explain how the eye starts the visual process.

LO 4.4 Identify the different kinds of visual perception.

LO 4.5 Describe different visual problems.LO 4.6 Explain how the ear starts the auditory

process.


Learning Objectives

LO 4.7 Identify the different kinds of auditory perception.

LO 4.8 Identify how we sense and perceive odors and tastes.

LO 4.9 Describe the three different body senses.LO 4.10 Explain how pain perception differs from

touch perception.LO 4.11 Describe the field of psychology called

human factors.LO 4.12 Track how our minds build up perceptions.


Learning Objectives

LO 4.13 Describe how we perceive people, objects, and sounds in our environment.

LO 4.14 Distinguish subliminal perception from subliminal persuasion.

LO 4.15 Analyze the scientific evidence for and against the existence of ESP.


Lecture Preview

• Sensation and perception• The visual system• The auditory system• Smell and taste• Our body senses• When our senses meet our brains


Sensation and Perception

• Sensation is the detection of physical energy by our sense organs, which send that information to the brain.

• Perception is the brain's interpretation of raw sensory data.

LO 4.1 Identify the basic principles that apply to all senses.


SensationLO 4.1 Identify the basic principles that apply to all senses.

• Despite their differences, all our senses rely on a handful of principles.

• The external stimulus is converted by a sense receptor into neural activity via transduction.

• Activation is highest when stimulus is first detected, then sensory adaptation occurs.


PsychophysicsLO 4.1 Identify the basic principles that apply to all senses.

• Study of how we perceive sensory stimuli based on their physical characteristics

• Absolute threshold is the lowest level of a stimulus we can detect 50% of the time– A single candle 30 miles away– 50 odorant molecules


PsychophysicsLO 4.1 Identify the basic principles that apply to all senses.

• The just noticeable difference is the smallest amount of stimulus change we can detect.

• Follows Weber's law—the stronger the stimulus, the greater the change necessary for the detection of a difference.


Figure 4.2 Just Noticeable Differences (JNDs) Adhere to Weber's Law. In this example, changes in light are shown measured in lumens, which are units equaling the amount of light generated by one candle standing one foot away. Weber's law states that the brighter the light, the more change in brightness is required for us to be able to notice a difference.


Signal Detection TheoryLO 4.1 Identify the basic principles that apply to all senses.

• Theory regarding how stimuli are detected under different conditions


Cross-Modal EffectsLO 4.1 Identify the basic principles that apply to all senses.

• Phosphenes, the McGurk effect, and the rubber hand illusion all demonstrate sensory cross-modality.

• This may help to explain synesthesia—the experience of cross-modal sensations, like hearing sounds when one sees colors.


The Role of Attention

• Selective attention allows us to choose which sensory inputs to focus on and which to "turn down."

• The other "channels" are still being processed at some level, though.– Cocktail party effect

LO 4.2 Discuss the role of attention and the nature of the binding problem.


The Role of AttentionLO 4.2 Discuss the role of attention and the nature of the binding problem.

• We're poor at detecting stimuli in plain sight if our attention is focused elsewhere.

• Inattentional blindness and change blindness are two similar phenomena.


Blinding ProblemLO 4.2 Discuss the role of attention and the nature of the binding problem.

• One of the great mysteries of psychology is just how our brains combine all the various stimuli around us into a coherent whole.

• The look, feel, smell, and taste of an apple all rely on different areas of the brain to process, but we just see an apple!


Light

• The human visible spectrum is a narrow band of light that we respond to.

• Other animals may have a more restricted or broader spectrum.

LO 4.3 Explain how the eye starts the visual process.


Figure 4.6 The Visible Spectrum Is a Subset of the Electromagnetic Spectrum. Visible light is electromagnetic energy between ultraviolet and infrared. Humans are sensitive to wavelengths ranging from slightly less than 400 nanometers (violet) to slightly more than 700 nanometers (red).


LightLO 4.3 Explain how the eye starts the visual process.

• We perceive brightness (intensity) and hue (color).

• Mixing lights produces white (additive).

• Mixing pigments produces black (subtractive).


Figure 4.7 Additive and Subtractive Color Mixing. Additive color mixing of light differs from subtractive color mixing of paint.


The EyeLO 4.3 Explain how the eye starts the visual process.

• Sclera is the white portion of the eye• Iris is the colored portion and controls

how much light enters the eye• Pupil is the hole where light enters the

eye



• Cornea contains transparent cells that focus light on the back of the eye

• The lens changes curvature (accommodation) to retract light onto back of eye.

• Glasses change the way light enters the eye to help correct myopia or hyperopia.


The RetinaLO 4.3 Explain how the eye starts the visual process.

• The retina is a thin membrane at the back of the eye.

• The fovea in its center is responsible for acuity.

• Light hits two types of sense receptors on the retina—rods and cones.– Dark adaptation


Figure 4.8 The Key Parts of the Eye.



• The optic nerve exits the back of the eye and is composed of the axons of the ganglion cells.– Causes a blind spot

• Most of the axons go to the thalamus and then the visual cortex, but some go to midbrain.


Figure 4.10 Perception and the Visual Cortex Visual information from the retina travels to the visual thalamus. Next, the visual thalamus sends inputs to the primary visual cortex (V1), then along two visual pathways to the secondary visual cortex (V2; see p. 136 ). One pathway leads to the parietal lobe, which processes visual form, position, and motion; and one to the temporal lobe, which processes visual form and color.


Perceiving Shape and Contour

• Different cortical cells respond maximally to different types of stimuli.

• Feature detector cells allow us to detect lines and edges.– Simple cells—detect orientation-specific

slits of light in a particular location– Complex cells—also orientation-specific,

but less dependent on location than simple cells

LO 4.4 Identify the different kinds of visual perception.


Color PerceptionLO 4.4 Identify the different kinds of visual perception.

• Different theories of color perception explain different aspects of our ability to detect color.

• Trichromatic theory says color vision is based on our sensitivity to three primary colors.– Consistent with three types of cones in

eyes– Explains color blindness


Color PerceptionLO 4.4 Identify the different kinds of visual perception.

• Opponent process theory sees color vision as a function of complementary, opposing colors: red v. green or blue vs. yellow.

• As an example, stare at the white dot in the middle of the flag on the next slide see what happens.


Figure 4.13 Opponent Processes in Action. Find a patch of blank white wall or place a blank sheet of white paper nearby before you begin. Then relax your eyes and fix your gaze on the white dot in the image above for at least 30 seconds without looking around or away. Afterward, stare at the white wall or paper for a few seconds. What do you see?


When We Can't See

• Blindness—results in heightened touch, reorganization of visual cortex

• Blindsight—above-chance visual performance of cortically blind individuals with damage to area V1

• Visual agnosia—object recognition deficit; damage to higher visual cortical areas

LO 4.5 Describe different visual problems.


Hearing and Sound

• Audition (our sense of hearing) is the sense we rely on most after sight.

• Sound is simply vibration traveling through a medium (usually air) and has:– Pitch—wave frequency (Hz)– Loudness—amplitude of the sound

waves (dB)– Timbre—complexity of sound

LO 4.6 Explain how the ear starts the auditory process.


The EarLO 4.6 Explain how the ear starts the auditory process.

• The outer, middle, and inner ear do different jobs to transduce sound into neural activity.

• The outer ear (pinna and ear canal) tunnels sound waves onto the eardrum.

• On the other side of the eardrum, the ossicles (hammer, anvil, stirrup) vibrate and transmit sound to the inner ear.


The EarLO 4.6 Explain how the ear starts the auditory process.

• In the inner ear, the cochlea converts vibration into neural activity.

• The organ of Corti and basilar membrane convert auditory information into action potentials.


Figure 4.16 The Human Ear and Its Parts. A cutaway section through the human ear and a close-up diagram of the hair cells.


Pitch PerceptionLO 4.7 Identify the different kinds of auditory perception.

• Place theory – Different tones excite different areas of the basilar membrane and primary auditory cortex.– Explains perception of high-pitched

tones


Pitch PerceptionLO 4.7 Identify the different kinds of auditory perception.

• Frequency theory and volley theory – Neurons' rate of firing reproduces the frequency of the sound.– Explains perception of low and middle

pitches


Smell and Taste

• Olfaction (smell) and gustation (taste) work hand in hand.

• Work together to enhance liking or disliking of some foods

• Described as the "chemical senses"



Odors and FlavorsLO 4.8 Identify how we sense and perceive odors and tastes.

• Odors are airborne chemicals that interact with lining in our nasal passages.

• We are sensitive to five basic tastes:– Sweet, salty, sour, bitter, umami– There is some evidence for a "fatty"

taste as well.


Smell and Taste Sense ReceptorsLO 4.8 Identify how we sense and perceive odors and tastes.

• Each olfactory neuron contains a single type of receptor, which recognizes odorants based on their shape.

• The tongue contains separate taste buds for each basic taste.– 25% of people are supertasters, with

more taste buds.


Olfactory and Gustatory Perception


• Although they take different paths, our smell and taste senses converge in the orbitofrontal cortex.


Figure 4.20 Smell and Taste. Our senses of smell and taste enter the brain by different routes but converge in the orbitofrontal cortex.


Our Body Senses

• Three body systems that work in tandem:– Somatosensory (touch and pain)– Proprioception (kinesthetic sense –

body position)– Vestibular sense (equilibrium and

balance)

LO 4.9 Describe the three different body senses.


Somatosensory SystemLO 4.9 Describe the three different body senses.

• Responds to pressure, temperature, and injury

• We sense these with specialized nerve endings in the skin and with free nerve endings.


Figure 4.21 The Sense of Touch. The skin contains many specialized and free nerve endings that detect mechanical pressure, temperature, and pain.


Somatosensory PathwaysLO 4.9 Describe the three different body senses.

OR


Pain Sensations

• Pain comes in many types, usually related to the pain-causing stimulus.

• Gate control model – pain is blocked from consciousness by neural mechanisms in the spinal cord.

• Pain is influenced by emotional and cultural factors.

LO 4.10 Explain how pain perception differs from touch perception.


Body Position and BalanceLO 4.9 Describe the three different body senses.

• Proprioception, our kinesthetic sense, helps us keep track of where we are, allowing us to move efficiently.

• Muscle stretch receptors vs. tendon force detectors


Body Position and BalanceLO 4.9 Describe the three different body senses.

• Vestibular sense, our sense of equilibrium, enables us to sense and maintain our balance as we move about.

• Due to three fluid-filled semicircular canals in the inner ear

• Our awareness of this sense is limited.


Ergonomics: Human Engineering

• Human factors – field that optimizes technology to better suit our sensory and perceptual capabilities

• Uses what we know about psychology and sensory systems to build more ergonomic gadgets and tools

LO 4.11 Describe the field of psychology called human factors.


When Senses Meet the Brain

• After being transduced, our brains then organize the sensory data into meaningful concepts.

• Our brains piece together: – What's in our sensory field– What was there a moment ago– What we remember from our past

LO 4.12 Track how our minds build up perceptions.


The Multitasking BrainLO 4.12 Track how our minds build up perceptions.

• We attend to multiple senses at once, called parallel processing.

• Bottom-up vs. top-down processing– Perception depends on sensory data and

beliefs/expectations.


Figure 4.23 What Do You See? Due to the influence of top-down processing, reading the caption "saxophone player" beneath this ambiguous figure tends to produce a different perception than reading the caption "woman."


Perceptual HypothesesLO 4.12 Track how our minds build up perceptions.

• Perceptual sets occur when our expectations influence our perceptions.



H or A?



Old or young?



• Perceptual constancy allows us to perceive stimuli consistency across conditions.

• We don't see the size, shape, or color of an object changing despite the objective fact that they do.

• Color perception in particular derives from context.


Figure 4.26 Shape Constancy. We perceive a door as a door whether it appears as a rectangle or a trapezoid.


Figure 4.27 The Checker-Shadow Illusion. We perceive a checkerboard pattern of black and white alternating squares, and because of color constancy, we ignore the dramatic change due to the shadow cast by the green cylinder. Believe it or not, the A and B squares are identical. (Source: © 1995 Edward H. Adelson)


Figure 4.28 Color Perception Depends on Context. Gray can appear like a color depending on surrounding colors. The blue-colored squares on the top of the cube at the left are actually gray (see map below the cube). Similarly, the yellow-colored squares on the top of the cube at the right are actually gray (see map below the cube). (Source: © Dale Purves and R. Beau Lotto, 2002)


Gestalt PrinciplesLO 4.12 Track how our minds build up perceptions.

• Rules that govern how we perceive objects as wholes within their overall context


Figure 4.30 Gestalt Principles of Perception. As Gestalt psychologists discovered, we use a variety of principles to help us organize the world.


Face Perception

• Depends on neurons in the lower part of the temporal lobe and in the hippocampus

• Though some neurons respond selectively to specific faces, face perception depends on broad neural networks.

LO 4.13 Describe how we perceive people, objects, and sounds in our environment.


Motion PerceptionLO 4.13 Describe how we perceive people, objects, and sounds in our environment.

• To determine motion, the brain compares visual frames of what is to what was.– Phi phenomenon

• Motion blindness—inability to perceive seamless motion


Motion PerceptionLO 4.13 Describe how we perceive people, objects, and sounds in our environment.

Image from Wikimedia Commons


Localizing SoundLO 4.13 Describe how we perceive people, objects, and sounds in our environment.

• We rely on binaural cues to tell us where sounds are coming from.

• These cues include differences between the two ears in the timing and intensity of sound waves.


Depth PerceptionLO 4.13 Describe how we perceive people, objects, and sounds in our environment.

• Monocular depth cues rely on one eye.– Relative size, texture gradient,

interposition, linear perspective, height in plane, light and shadow

• Binocular depth cues require both eyes.– Binocular disparity and binocular

convergence


When Perception Deceives UsLO 4.13 Describe how we perceive people, objects, and sounds in our environment.

• We often misperceive information around us and understanding why provides insight into how we make sense of our surroundings.

• Examples of such misperception include the moon illusion; the Ames room; and the Muller-Lyer, Ponzo, vertical-horizontal, and Ebbinghaus illusions.


Figure 4.35 How Well Can You Judge Relative Size?


Subliminal Perception

• We process many sensory inputs unconsciously and many of our actions occur with little to no forethought or deliberation.

• If we can detect stimuli without knowing it, does that change our behavior?

LO 4.14 Distinguish subliminal perception from subliminal persuasion.


Subliminal PerceptionLO 4.14 Distinguish subliminal perception from subliminal persuasion.

• The processing of sensory information that occurs below the level of conscious awareness

• Can have a brief, short-term impact on behaviors and attitudes

• Effect disappears when subjects are aware of or suspect subliminal influences


Subliminal PersuasionLO 4.14 Distinguish subliminal perception from subliminal persuasion.

• Fairly unlikely to produce large-scale or enduring changes in attitudes or decisions

• Subliminal self-help tapes have been shown to be ineffective.

• Reversed subliminal messages are also ineffective.


Extrasensory Perception

• The perception of events outside the known channels of sensation

• According to parapsychologists, there are three major types:– Precognition– Telepathy– Clairvoyance



Evidence for ESPLO 4.15 Analyze the scientific evidence for and against the existence of ESP.

• Early studies by Rhine (1934) using Zener cards reported positive results.

• But, methodological problems plagued the study and no one could replicate his results.



Photo 4.27 Zener cards



• Ganzfield technique studies, fMRI studies, and others all fail to find positive effects for ESP.

• ESP proponents explain away negative findings, citing such factors as experimenter effects.

• These are ad-hoc explanations, though.


Why People BelieveLO 4.15 Analyze the scientific evidence for and against the existence of ESP.

• Over 40% of American adults believe in ESP.

• Why?– Illusory correlations– Not understanding chance events

underestimating the likelihood of coincidences



How many people must be in a room before there is a 50% chance that two will share a birthday?


Figure 4.36 The "Birthday Paradox." As we reach a group size of 23 people, the probability that at least two people share the same birthday exceeds 0.5, or 50 percent. Research demonstrates that most people markedly underestimate the likelihood of this and other coincidences, sometimes leading them to attribute these coincidences to paranormal events.


Failed Psychic PredictionsLO 4.15 Analyze the scientific evidence for and against the existence of ESP.

• Specific predictions ("Nazi flag found on moon!") do not come true.

• So "psychics" use other methods to make it seem as if they are accurate.– Multiple end points– Cold reading techniques

PSYCHOLOGY from inquiry to understanding CHAPTER THIRD EDITION Copyright © 2014, © 2011, © 2009 by Pearson Education, Inc. All Rights Reserved Sensation.

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