Sensation (1 of 6) LO 4.1a Identify the basic principles that apply to all senses. 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. Bottom-up vs. top-down processing Perception depends on sensory data and beliefs/expectations.

Sensation/Perception Transduction: sensory receptors convert a physical energy into nerve impulses © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Sensation (2 of 6) LO 4.1a 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.

Sensory Thresholds Psychophysics: testing limits and changes Absolute Threshold: smallest amount of a stimulus we can detect Difference Threshold: minimal difference needed to detect a a stimulus change; also called the just noticeable difference (JND) © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Sensation (4 of 6) LO 4.1a 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 4.1 Just Noticeable Differences (JNDs) Adhere to Weber’s Law

Signal Detection Theory © 2011 The McGraw-Hill Companies, Inc.

Figure 4.4 The Visible Spectrum Is a Subset of the Electromagnetic Spectrum.

Physical/Perceptual properties of light © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Properties of Light wavelength: distance between peaks perceived as hue some wavelengths beyond human sensation amplitude: height of wave perceived as brightness purity: mixture of wavelengths perceived as saturation © 2011 The McGraw-Hill Companies, Inc.

Light (2 of 2) LO 4.2a 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 4.5 Additive and Subtractive Color Mixing

Figure 4.6 The Key Parts of the Eye

The Eye (1 of 7) LO 4.2a Explain how the eye starts the visual process. The sclera is the white portion of the eye. The iris is the colored portion and controls how much light enters the eye. The pupil is the hole where light enters the eye.

The Eye (2 of 7) LO 4.2a Explain how the eye starts the visual process. The 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.

Eye as optical instrument Light refraction © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

The Eye (3 of 7) LO 4.2a 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

Structure of the Eye: Retina © 2011 The McGraw-Hill Companies, Inc.

Structure of the Eye: Retina Rods sensitive to even dim light, but not color function well in low illumination humans have ≈ 120 million rods Cones respond to color operate best under high illumination humans have ≈ 6 million cones © 2011 The McGraw-Hill Companies, Inc.

The Eye (4 of 7) LO 4.2a Explain how the eye starts the visual process. 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 4.8 Perception and the Visual Cortex

Color Perception Humans are able to discriminate 7 million different hues. Colors convey important information: Ripeness of food Danger signals Trichromatic theory Eye contains 3 different color sensitive elements Blue, green or red elements Trichromatic theory accounts for color mixing of lights. Opponent-Process theory Visual system is organized into red-green, blue-yellow and black-white units. Theory can account for negative color afterimages. © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Figure 4.12 Afterimages: Opponent Processes in Action

When We Can’t See or Perceive Visually LO 4 When We Can’t See or Perceive Visually LO 4.2c Describe different visual problems. 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

Sound LO 4.3a Explain how the ear starts the auditory process. 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

Figure 4.14 The Audible Spectrum (in Hz)

Sound Loudness (dB) © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Figure 4.15 The Human Ear and Its Parts

The Structure and Function of the Ear (1 of 4) LO 4 The Structure and Function of the Ear (1 of 4) LO 4.3a 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 Structure and Function of the Ear (2 of 4) LO 4 The Structure and Function of the Ear (2 of 4) LO 4.3a 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.

Cross-section of cochlea © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Theories of Hearing Place Theory of Pitch Perception location of stimulation is important only explains perception of high frequencies Frequency Theory of Pitch Perception frequency of nerve firing limitations of neuronal firing rate volley principle cell clusters can exceed limitations of firing rate © 2011 The McGraw-Hill Companies, Inc.

Hearing Loss Conduction deafness: Middle-ear deafness resulting from problems with transferring sound waves to the inner-ear. Nerve Deafness: Inner-ear deafness resulting from damage to the cochlea, hair cells, or auditory nerve. © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Smell and Taste LO 4.4a Identify how we sense and perceive odors and tastes. Olfaction (smell) and gustation (taste) work hand in hand. Work together to enhance liking or disliking of some foods Described as the “chemical senses”

What Are Odors and Flavors. LO 4 What Are Odors and Flavors? LO 4.4a 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. Although they take different paths, our smell and taste senses converge in the orbitofrontal cortex.

Figure 4.19 Smell and Taste

Form Perception: Gestalt Principles Source: Based on psychologists Max Wetheimer, Wolfgang Kohler, and Kurt Koffka

Perceptual Constancies 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.

Figure 4.25 Shape Constancy

Size Constancy © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

The Checker-Shadow Illusion: Lightness or Color Constancy Source: © 1995 Edward H. Adelson

Perceptual Hypotheses (6 of 7) LO 4 Perceptual Hypotheses (6 of 7) LO 4.6b Describe how we perceive people, objects, and sounds in our environment. Depth perception 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

Monocular Cues © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E

Retinal Disparity © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 7E