Chapter four Sensation and Perception Understanding sensation How

Chapter four Sensation and Perception • • Understanding sensation How we see and hear Our other important senses Understanding perception © 2014 John Wiley & Sons, Inc. All rights reserved.

realworldpsychology Things You’ll Learn in Chapter 4 Q 1 Do athletes have a higher pain tolerance than non -athletes? Q 2 Can looking at a photograph of a loved one lead you to feel less pain? Q 3 How can listening to loud music on headphones damage your hearing? Q 4 Why do premature babies grow faster when they receive skin-to-skin contact? Q 5 Why do people rate themselves as more athletic if they compare themselves to the Pope than to a professional basketball player? © 2014 John Wiley & Sons, Inc. All rights reserved.

Understanding Sensation • While your brain floats in complete silence and darkness, your body is bombarded with stimuli from outside. What are • Sensing the stimuli is not some of these enough – our brains must stimuli? receive, convert and adapt the information into meaningful representations of the world © 2014 John Wiley & Sons, Inc. All rights reserved.

Understanding Sensation • Sensation = process of detecting, converting and transmitting raw sensory information from the external and internal environments to the brain • Perception = process of selecting, organizing, and interpreting sensory info into meaningful patterns © 2014 John Wiley & Sons, Inc. All rights reserved.

UNDERSTANDING SENSATION © 2014 John Wiley & Sons, Inc. All rights reserved.

Sensation: the basics 1. Receptor cells in sense organs detect appropriate stimuli 2. Convert stimuli (transduction) into neural impulses (action potential) 3. Transmit message to brain through different routes, allowing brain to differentiate physical stimuli (coding) 4. Brain assigns meaningful sensory information © 2014 John Wiley & Sons, Inc. All rights reserved.

Stimulation Overload? • Some brain structures purposely reduce some sensory information they receive • What types of things can humans What if this sensory not detect? – Ultraviolet light, microwaves, dog whistle, infrared heat patterns reduction didn’t occur? • Field of psychophysics studies link between physical stimuli and psychological experience © 2014 John Wiley & Sons, Inc. All rights reserved.

What Can We Detect? • Consciously aware of only a narrow range of stimuli at one time • Difference Threshold (AKA Weber’s Law of just noticeable differences or JND) = minimal difference in stimulus strength that is detectable 50% of the time (Ernst Weber) • Absolute Threshold = minimum stimulation needed to consciously detect stimulus 50% of the time (Gustav Fechner) How could these be measured? © 2014 John Wiley & Sons, Inc. All rights reserved.

Subliminal Stimuli • Studies on subliminal perception use a tachistoscope to flash images too quickly for conscious perception (but slowly enough for the brain to register them) • At the movies “eat popcorn”? satanic verses when music is played backward? hidden sexual messages in Disney films? Can subliminal stimuli change your behavior? • Subliminal stimuli are WEAK and don’t lead to subliminal persuasion © 2014 John Wiley & Sons, Inc. All rights reserved.

Sensory Adaptation • Suppose you visit a neighbor’s house with 10 cats. You smell the animals, but the owner doesn’t. Why • Sensory adaptation = when a constant stimulus not? is presented, the sensory receptors become less sensitive and fire less frequently • Normally, smell and touch experience sensory adaptation readily; vision and intense stimuli do not. Why? What perspective in psychology might explain this? © 2014 John Wiley & Sons, Inc. All rights reserved.

realworldpsychology • Intense pain often resists sensory adaptation to signal danger Q 1 Do athletes have a higher pain tolerance than non-athletes? • Endorphins are the body’s natural painkiller and are released during physical exertion – Does the experience of playing sports change pain tolerance? – Or are people with high pain tolerance drawn to athletics? © 2014 John Wiley & Sons, Inc. All rights reserved.

What about pain? • Gate-control theory = experience of pain depends on whether the message gets past the “gatekeeper” in the spinal cord – Normally, the gate is shut and pain signals are blocked, but when body tissue is damaged, impulses open the gate to allow the message of pain through – Messages from the brain also control the gate, allowing some to continue through the pain (athletes, military, first responders) © 2014 John Wiley & Sons, Inc. All rights reserved.

realworldpsychology • Massaging an injury eases discomfort because pressure on larger-diameter neurons interferes with pain signals Q 3 Can looking at a photograph of a loved one lead you to feel less pain? • Endorphins from the brain, distraction by fear or competition, actively listening to music – or looking at a picture – can close the gate and reduce pain and anxiety • Focusing on pain amplifies it © 2014 John Wiley & Sons, Inc. All rights reserved.

What about pain? • Phantom limb pain = when amputee continues to feel sensations (pain, tickling) in the missing limb • Nerve cells send conflicting messages to the brain, producing “static” that is interpreted as pain • Prosthetic limbs and mirror visual therapy can help reduce phantom limb pain © 2014 John Wiley & Sons, Inc. All rights reserved.

HOW WE SEE AND HEAR © 2014 John Wiley & Sons, Inc. All rights reserved.

Vision • Receptor cells in retina (rods and cones) convert light waves into messages sent along the optic nerve © 2014 John Wiley & Sons, Inc. All rights reserved.

Vision Problems • Visual acuity problems result from small abnormalities in the shape of the eye, causing the image not to be in focus at the retina – Nearsightedness – image reaches focus in front of the retina – Farsightedness – image reaches focus behind the retina • Presbyopia – lenses lose elasticity with age • Blind spot – no receptor cells where the optic nerve exits the eye • Rods manage dark adaptation – changing from sunny to dark environment leaves you temporarily blind • Cones manage light adaptation – changing from dark to bright environment activate cones © 2014 John Wiley & Sons, Inc. All rights reserved.

Hearing • Outer ear captures sound, three tiny bones in middle ear transmit eardrum’s vibration to the inner ear where cochlea transforms waves into neural impulses © 2014 John Wiley & Sons, Inc. All rights reserved.

Pitch and Volume • Frequency of sound waves provides information about pitch of sound – Place theory for hearing = hair cells at different locations along the basilar membrane are stimulated by highpitched sounds – Frequency theory for hearing = hair cells vibrate at the same low frequency as the low-pitched sounds they detect • Loud sounds have higher peaks and lower valleys than soft sounds, measured by decibels © 2014 John Wiley & Sons, Inc. All rights reserved.

Hearing Problems • Conduction hearing loss (conduction deafness) = problems with mechanics of sending sound waves to cochlea. Hearing aids and some surgery help • Sensorineural hearing loss (nerve deafness) = damage to hair cells or auditory nerve Q 3 How can listening to loud music on headphones damage your hearing? • Result of loud noise, disease, and biological changes; damage to receptor cells and auditory nerve is irreversible © 2014 John Wiley & Sons, Inc. All rights reserved.

OUR OTHER IMPORTANT SENSES © 2014 John Wiley & Sons, Inc. All rights reserved.

Smell • Smell and taste are “chemical senses” because they use chemoreceptors and are sensitive to chemical molecules • Olfactory receptors in the nose transduce info from odorants (molecules with odor) directly to olfactory bulb at base of frontal lobe, where info is processed and sent to other brain regions • Olfaction is the only sensory system NOT routed through the thalamus © 2014 John Wiley & Sons, Inc. All rights reserved.

Taste • Purpose of taste is to avoid poisonous foods (which are usually bitter); nonpoisonous foods with good energy are often sweet • Dissolved food particles pass over papillae on the tongue and down into taste buds (taste receptors), which transduce info to the brain • Taste buds are distributed all over the tongue, NOT in dedicated regions by taste • Umami – savory; sensitivity to glutamate found in meat, broth, MSG © 2014 John Wiley & Sons, Inc. All rights reserved.

Taste Preferences Shaped in Utero Mennella, Jagnow & Beauchamp, 2001 • Group 1: carrot juice 4 x week for 3 weeks during pregnancy • Group 2: carrot juice 4 x week for 3 weeks after baby was born (breast-feeding mothers) • Group 3: no carrot juice • Mothers rated babies’ facial reactions to different foods and quantity of carrot-flavored cereal baby would eat • Babies exposed to carrots in utero or through breast milk liked the taste of carrots better © 2014 John Wiley & Sons, Inc. All rights reserved.

Body Senses – Skin Sense • Skin sense detects pressure, temperature, and pain • Touch receptors are most concentrated in face and hands (that’s why paper cuts hurt!) Q 4 Why do premature babies grow faster when they receive skin-to-skin contact? • Kangaroo care – skin-to-skin contact between mother and baby recommended immediately after birth, especially for low-birth-weight babies • Provides warmth, reduces pain, lowers stress arousal, improves sleep, which leads to growth © 2014 John Wiley & Sons, Inc. All rights reserved.

Body Senses - Vestibular • Vestibular sense tells the brain how our body (especially head) is oriented in 3 -dimensional space • Hair cells in the semicircular canals of the inner ear and in the vestibular sacs transduce the position of the head into neural impulses © 2014 John Wiley & Sons, Inc. All rights reserved.

Body Senses - Kinesthesis • Kinesthesis provides information about body posture, orientation and movement of individual body parts • Kinesthetic receptors in muscles, joints, and tendons tell the brain what is moving, how weight is distributed, where body parts are in relation to the whole © 2014 John Wiley & Sons, Inc. All rights reserved.

UNDERSTANDING PERCEPTION Perception = process of selecting, organizing, and interpreting incoming sensations into useful mental representation of the world © 2014 John Wiley & Sons, Inc. All rights reserved.

Perception Problems • “Seeing is believing, but seeing isn’t always believing correctly” (Lilienfeld et al, 2010, p. 7) What does this mean? • Illusion = false or misleading impression produced by errors in the perceptual process or by actual physical distortions • Illusions are NOT the same as hallucinations (false sensory experience WITHOUT external stimuli) or delusions (false beliefs) © 2014 John Wiley & Sons, Inc. All rights reserved.

Selection • Cannot pay attention to all stimuli • Selective attention = paying attention to important information and filtering the rest • Feature detectors = specialized neurons to respond to specific stimuli, like faces – Prosopagnosia – inability to identify person by facial features • Habituation = decrease in responding to repeated stimulation of same stimuli; more responsive to changes in environment – Compliments from strangers are more exciting than from longterm partner! – The song you HATED on first listen might grow on you! © 2014 John Wiley & Sons, Inc. All rights reserved.

realworldpsychology • How do advertisers and political campaigns use selective attention, feature detectors, and habituation? • Capture attention with intense, novel, moving, contrasting stimuli and repetition © 2014 John Wiley & Sons, Inc. All rights reserved.

Organization: Form Perception • Gestalt psychologists studied how the brain organizes sensory impressions into a “form” or “whole” • Figure-Ground: objects are distinct from the background © 2014 John Wiley & Sons, Inc. All rights reserved.

Organization: Depth Perception • Depth Perception: ability to perceive 3 dimensional space using binocular and monocular cues re a lw o r l dp s y c h o l o g y • Visual cliff: crawling infants refuse to move to the “deep end” © 2014 John Wiley & Sons, Inc. All rights reserved.

Organization: Constancies Perception • Perceive the environment as stable, despite changes in object’s size, shape, color and brightness Why is this important? © 2014 John Wiley & Sons, Inc. All rights reserved.

Organization: Color Perception • Trichromatic theory of color = three “color systems”, each of which is sensitive to red, green and blue; mixing lights of these three colors yields the full spectrum of colors • Opponent-process theory = each of the color systems is sensitive to two opposing colors (ex: either blue or yellow) – Black-and-white systems respond to differences in brightness © 2014 John Wiley & Sons, Inc. All rights reserved.

© 2014 John Wiley & Sons, Inc. All rights reserved.

Color-Deficient Vision • Color confusion on specific color spectrums, such as red-green or blue-yellow Is anyone here “colorblind”? What is it like? © 2014 John Wiley & Sons, Inc. All rights reserved.

Organization: Interpretation • Perceptual set = readiness to perceive stimuli in a particular manner, based on expectations • We see what we expect to see • Frame of reference = perception is influenced by context Q 5 Why do people rate themselves as more athletic if they compare themselves to the Pope than to a professional basketball player? © 2014 John Wiley & Sons, Inc. All rights reserved.

Processing • Bottom-up processing = raw sensory data “sent up” to the brain for higher level analysis • Top-down processing = perceptual analysis starts “at the top” with expectations and knowledge driving the process of perception • You learn to read from bottom-up processing of letters and words • Now, your aiblity to raed uisng top-dwon prcessoing mkes it psosible to unedrstnad this sntenece desipte its mnay mssiplllengis © 2014 John Wiley & Sons, Inc. All rights reserved.

Sixth Sense? • Extrasensory Perception (ESP) = “psychic” perceptual abilities that supposedly go beyond the known senses – Telepathy, clairvoyance, precognition • Research in ESP don’t withstand scrutiny, failure to replicate by rival research labs • Why do some believe in ESP? – Motivation and interests influence our perceptions, creating selective perception – Strong emotions about the subject mask faulty reasoning © 2014 John Wiley & Sons, Inc. All rights reserved.

© 2014 John Wiley & Sons, Inc. All rights reserved.