© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E PSYCHOLOGY IN ACTION Sixth Edition by Karen Huffman PowerPoint  Lecture Notes Presentation Chapter 4 Sensation & Perception Paul J. Wellman Texas A&M University

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Lecture Overview Experiencing Sensations Vision Other Senses Perception –Selection –Organization –Interpretation

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Sensation and Perception Sensation is the process of receiving, converting, and transmitting information from the outside world –Sensory organs contain receptors that transduce sensory energy into nerve impulses that are carried to the brain Perception involves organization and interpretation of sensory input –Interpretation of sensory input is an active process –Perceptions can differ among people Top-down processing versus bottom-up processing

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Sensation/Perception Transduction: sensory receptors convert a physical energy into nerve impulses

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Sensory Thresholds Each sensory system has a threshold level of energy that is required to activate that sense –Absolute threshold: The smallest amount of energy that can be detected by a system –Difference threshold: The smallest difference in sensory energies that can be detected Different people can have widely varying sensory thresholds Thresholds can change within a person over time and as a function of hormone status –Olfactory sensitivity during pregnancy –Ability to taste foods as we get older

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Modification of Sensation A key function of sensory systems is to detect change within the environment –Movement in the peripheral aspects of the eye may signal food or danger –Constant pressure of an object on the skin may not be important A stimulus that moves across the skin may be a snake or a spider The skin adapts to constant pressure –Constant pain is unpleasant and wastes body resources Pain is offset by a control system involving opiates

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Vision External light falls on receptors within the eye to generate the visual message Light = electromagnetic radiation –Wavelength of light determines color

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Anatomy of the Eye

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Photoreceptors Photoreceptors are light-sensitive cells found within the retina –Rods are sensitive to light, but not color, and are active under low-light conditions –Cones are sensitive to color, are not active in low-light conditions, and allow for fine detail –Rods and cones use different photopigments that react to light so as to generate nerve potentials

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Retinal Photoreceptors Light passes through the retinal layers to reach the photoreceptors at the inner retinal surface Photoreceptors and bipolar cells conduct potentials to the ganglion cells, which in turn initiate action potentials which are transmitted to the thalamus

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Sensory Coding Activation of retinal cells by light results in action potentials that travel along neurons that project to the occipital cortex

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Hearing Receptors within the ear are tuned to detect sound waves (changes in sound pressure level) –Sound waves vary in terms of Frequency: corresponds to pitch Amplitude: corresponds to loudness Sound loudness is measured in decibels

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Sound Loudness (dB)

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Anatomy of the Ear (Sound Waves)

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Pitch and Loudness Sound waves vibrate the basilar membrane within the cochlea of the ear –Hair cells containing receptors bend in response to vibration of the membrane –Hair cells trigger action potentials that are carried to the auditory cortex –Different frequencies produce maximal vibration of different areas along the membrane: produces place coding of pitch

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Perception Perceptual processes include –Selection refers to choosing which of many stimuli that will be processed –Organization involves collecting the information into some pattern –Interpretation involves understanding the pattern Perceptions can be in error –Illusions are visual stimuli that are misinterpreted

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Horizontal-Vertical Illusion WHICH LINE IS LONGER?

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Form Perception Figure and background are basic organizational themes for perception Gestalt psychologists examined properties that make for a good figure –Figure is perceived as distinct from the background –Figure is closer to the viewer than the background

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Gestalt Organizational Principles

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Color Perception Humans are able to discriminate 7 million different hues Colors convey important information –Ripeness of food –Danger signals (traffic lights; for some people…) 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

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Extrasensory Perception ESP refers to the ability to perceive stimuli that are outside the 5 senses –Telepathy: the ability to read minds –Clairvoyance: the ability to perceive objects or events –Precognition: the ability to predict the future –Psychokinesis: the ability to move objects

© 2002 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN ACTION, 6E Copyright Copyright 2002 by John Wiley & Sons, Inc., New York, NY. All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission of the copyright owner.