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Psychology 1000: Chapter 5-8 Midterm.docx

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Western University
Psychology 1000
Laura Fazakas- De Hoog

Chapter 5 – Sensation and Perception  Sensation – the stimulus-detection process by which our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to the brain  Perception – active process of organizing the stimulus input and giving it meaning Sensory Processes  Stimulus detection – absolute threshold designated as the lowest intensity at which a stimulus can be detected 50% of the time  Signal detection theory – concerned with the factors that influence sensory judgments o Decision criterion – standard of how certain a person must be that a stimulus is present before they will say they detect it o Increased rewards for noticing stimuli often results in lower detection thresholds o Increased danger/punishment for noticing stimuli often raises detection threshold  Difference threshold – smallest difference between two stimuli that can be perceived 50% of the time (just noticeable difference – jnd) o Weber’s Law – to perceive a difference between two stimuli, one must differ by a constant ratio  Value for weights = 1/50, therefore if 50 lbs. is lifted, increased weight will only be detected at 51 lbs.  Smaller fraction = higher sensitivity  Doesn’t apply to extremely high or low stimulation intensities  Sensory adaptation – the diminishing sensitivity to an unchanging stimulus o Perception of stimuli will decrease if constantly present The Sensory Systems Vision  The Human Eye o Light enters eye through cornea (transparent protective structure) o Pupil – adjustable opening that dilates or constricts to control amount of light entering o Iris – controls the pupil o Lens – elastic structure that becomes thinner to focus on distant objects and thicker to focus on nearby objects  Image flipped and reversed onto retina  Ability to see clearly depends on lens’ ability to focus image onto retina  Myopia (nearsightedness) – lens focuses image in front of retina  Hyperopia (farsightedness) – lens focuses image behind retina o Retina – multi-layered tissue at rear of eyeball  Photoreceptors: Rods and Cones o Retina covered in light-sensitive receptor cells o Rods – black and white receptors  Function best in dim light o Cones – color receptors  Function best in bright light o In humans, rods are everywhere except fovea (direct center of retina)  Cones decrease in concentration distant from the fovea o Rods and cones send message to brain via two additional layers of cells  Bipolar cells have synaptic connections with rods and cones  Bipolar cells synapse with ganglion cells, whose axons form into optic nerve o Cones in the fovea each have private line to a single bipolar cell (unlike others, which have many rods/cones for each bipolar cell)  Visual acuity (ability to see fine detail) increases with image directly on fovea o Blind spot exists at point where ganglion cells exit to form optic nerve  Transduction - process where characteristics of a stimulus are converted into nerve impulses o Rods and cones accomplish transduction through photopigments o Absorption of light be photopigments increases release of neurotransmitters  Brightness Vision and Dark Adaptation o Dark adaptation – the progressive improvement in brightness sensitivity that occurs over time in low illumination  Cones adapt completely in 10 minutes  Rods continue adapting for 30 minutes, allowing extreme sensitivity to light  Color vision o Trichromatic theory – three types of color receptors in retina (blue, green, red)  All colors produced by combination of wavelengths between these three colors  Flaws in theory:  Yellow produced by red and green, yet people with red-green color blindness can see yellow  Color afterimage (image in different color appears after stimulus shown for a while then withdrawn) o Opponent-process theory – three color receptors, each responding to two different wavelengths (red-green, blue-yellow, black-white)  Explains color afterimage issue o Dual processes in color transduction  Modern dual-process theory combines both theories to account for color transduction process  Cones contain one of three different photopigments that are sensitive to blue, green, and red  Different combinations of intensities will produce different colors  Opponent processes occur, but not in cones  Ganglion cells respond in opponent-process by altering firing rate o Color-deficient vision  Dichromat – color blind to only one system (red-green or yellow-blue)  Monochromat – completely colorblind (only sees black-white)  Analysis and Reconstruction of Visual Scenes o Feature detectors  Optic nerve sends nerve impulses to brain (thalamus, then primary visual cortex)  Groups of neurons in the cortex are organized to receive and integrate sensory nerve impulses from specific regions of retina  Feature detector cells fire selectively to stimuli that have specific characteristics  Certain cells fire when horizontal line present, others when other angles present  Parallel processing – different cells analyze stimuli and construct unified image of its properties o Visual association processes  Information analyzed and reconstructed in primary visual cortex is routed to other regions known as visual association cortex Audition  Frequency – number of sound waves or cycles per second (Hz = one cycle per second)  Amplitude – vertical size of the sound waves (decibels – db)  Transduction system of ear is made up of bones, membranes, and tubes o Sound waves vibrate eardrum, which vibrates three bones (hammer, anvil, and stirrup)  Amplify sound waves more than thirty times o Cochlea – coiled, snail shaped tube that contain basilar membrane (sheet of tissue) o Organ of Corti rests on the basilar membrane  Has thousands of tiny hair cells that are actual sound receptors  Sound waves cause waves in liquid, which bend hairs, causing release of neurotransmitters  Sound localization – ability to notice location of sound due to timing difference in sound wave reception in ear  Two types of hearing loss: o Conduction deafness – problems involving the mechanical system that transmits sound waves to the cochlea o Nerve deafness – caused by damaged receptors within the inner ear, or damage to the auditory nerve Taste and Smell: The Chemical Senses  Taste (gustation) and smell (olfaction) are sensitive to chemical molecules rather than energy  Taste buds – chemical receptors along edges and back surface of tongue o Consists of bitter, sour, salty, and sweet receptors  Receptors of smell are long cells that project through the lining of the upper part of the nasal cavity and the mucous membrane  Pheromes – chemical signals found in natural body scents o Menstrual synchrony – tendency of women who live together to have similar menstrual cycles The Skin and Body Senses  Receptors in skin and internal organs sense pressure, pain, warmth, and cold o Mixtures form other sensations, such as itch  Kinesthesis – provides us with feedback about our muscles’ and joints’ positions and movements o Cooperates with the vestibular sense (sense of body orientation or equilibrium) Perception: The Creation of Experience  Two different types of processing functions: o Bottom up processing – takes individual elements of the stimulus and combines into a unified perception o Top down processing – sensory information is interpreted in the light of existing knowledge, concepts, ideas, and expectations  Accounts for psychological influences on perception Role of Attention in Perception  Attention involves processes of (1) focusing on certain stimuli, and (2) filtering out other incoming information o Studied through technique called shadowing  Participants hear two messages simultaneously through earphones, and must repeat one of the messages word for word  Most can complete this, but cannot repeat second message  Attention strongly influenced by nature and personal factors o Internal factors (motives and interests) influence which stimuli are noticed Perceptions Have Organization and Structure  Synthesia – stimuli in one sensory modality give rise to perceptions in other modalities  Gestalt theorists believe strongly in top-down processing o Wholes perceived are often more than the sum of their parts o Figure ground relations – perceptual organization in which a focal stimulus is perceived as a figure against a background of other stimuli o Gestalt laws of perceptual organization – four ways in which people group and interpret stimuli  Similarity – when parts of a perception are perceived as similar, they will be perceived as belonging together  Proximity – elements that are near one another are likely to be perceived as part of the same configuration  Closure – people tend to close the open edges of a figure or fill in gaps of an incomplete figure, so that their identification of the form is more complete  Continuity – people link individual elements together so that they form a continuous line or pattern that makes sense Perception Involve Hypothesis Testing  Perceptual schema – a mental representation or image of a stimulus to compare it with  Perception is an attempt to make sense of stimulus input, finding the best interpretation of sensory information that can be arrived at based on our knowledge and experience Perception is Influenced by Expectations  Perceptual set – a readiness to perceive a stimulus in a particular way based on expectations, motives, emotions, or beliefs Stimuli are Recognizable Under Changing Conditions  Perceptual constancies – ability to recognize stimulus characteristics under varying conditions o Example – ability to recognize both an open door and closed door as still being a door o Shape constancy allows the recognition of people and objects from many different angles o Brightness constancy causes the relative brightness of objects remains the same under different conditions of illumination Perception of Depth, Distance, and Movement  Brain translates information from retina (only in two dimensions – length and width) into three- dimensional perceptions using two cues: o Monocular depth cues – require only one eye  Use of light and shadow to create 3D image  Linear perception allows depth cues (two lines converging into the difference)  Interposition, height, clarity, and relative size also contribute o Binocular disparity – require both eyes  Perceptions from both eyes are combined into one image (example – 3D glasses)  Convergence – produced by feedback from muscles that turn eyes inward to view a near objects Perception of Movement  Primary cue for perceiving motion is movement of stimulus across the retina  Relative movement of an object against a structured background is a movement cue  Stroboscopic movement – illusory movement produced when a light is briefly flashed in darkness, and then, a few milliseconds later, another is flashed nearby o Light appears to move, though it is simply quick flashing of light in a movement pattern Illusions  Compelling but incorrect perceptions that can be understood as erroneous perceptual hypotheses about the nature of the stimulus  Size constancy may be distorted to create an illusion of distance Chapter 6 – States of Consciousness  Consciousness – our moment to moment awareness of ourselves and our environment o Has various characteristics:  Subjective and Private – reality and experience depend on the individual  Dynamic – consciousness experiences are ever-changing and a continuous flow of mental activity  Self-reflective and Central to Our Sense of Self – mind is aware of its own consciousness Levels of Consciousness  Freud proposed that the mind consists of three levels: o Conscious – contains thoughts, perceptions, and other mental events that we are aware of o Preconscious – outside of current awareness, but can be recalled under certain conditions (eg. Reminder is necessary) o Unconscious – cannot be brought into conscious awareness under ordinary circumstances (as it would arouse anxiety, guilt, or other negative emotions)  The Cognitive Unconscious o Reject notion of an unconscious mind driven by instinctive urges and repressed conflicts o View conscious mental life as complementary forms of information processing o Controlled vs. Automatic Processing  Controlled – voluntary use of attention and conscious effort (studying, planning, etc.)  Automatic – performed with little or no conscious effort (driving, etc.) o Divided Attention – ability to perform more than one activity at the same time  More difficult when tasks require similar mental resources  The Emotional Unconscious o Emotional and motivational processes also operate unconsciously and influence behaviour  The Modular Mind o Many models propose that the mind is a collection of largely separate but interacting modules o Information processing subsystems that perform tasks related to sensation, perception, memory, problem solving, etc. o Subjective experience of consciousness arises from the integrated activity of the various modules Circadian Rhythms: Our Daily Biological Clocks  Circadian rhythms – daily biological cycles within the body that occur on a 24 hour cycle  Most rhythms regulated by brain’s suprachiasmatic nuclei (SCN) in the hypothalamus o Linked to pineal gland, which secretes melatonin (relaxing hormone) at night when SNC is less active to reduce secretion  Gradual and sudden environmental changes can disrupt our circadian rhythms o Seasonal affective disorder – cyclic tendency to become psychologically depressed during certain months of the year o Jet lag caused by change in typical daily time cycle Sleep and Dreaming  Brain’s electrical activity mostly beta waves (high frequency, low amplitude) while awake  Alpha waves (lower frequency, slightly higher amplitude) while relaxed and frowsy Stages of Sleep  Stages 1 through 4 o Stage 1 – alpha waves turn into theta waves  Lasts a few minutes, can be easily awakened o Stage 2 – sleep spindles in brain-wave activity indicate transition to stage o Stage 3 – regular appearance of slow and large delta waves o Stage 4 – delta waves dominate brain wave activity  Within 60-90 minutes of falling asleep, stages proceed through 1-2-3-4-3-2  REM sleep – periods of sleep involving rapid eye movements o Periods of REM comes following stage 2 sleep o Period where dream occurs  Dreams can occur during non-REM sleep, but not as vivid o REM sleep paralysis – brain sends signals to make voluntary muscle movements more difficult  Body is highly aroused, but little or no muscle movement How Much Do We Sleep  Newborns began by sleeping 16 hours a day, almost half in REM  As people age, three important changes occur: o Sleep less (19-30 year olds: 8 hours average, elderly: under 6 hours average) o REM sleep dramatically decreases during early childhood, but remains stable afterwards o Time spent in stages 3 and 4 decline  Both genetics and environment can affect length of sleep  Sleep deprivation causes negative impact on functioning, mood, cognition, and physical performance Why Do We Sleep  Restoration model – sleep recharges our run-down bodies and allows us to recover from physical and mental fatigue o Researchers believe adenosine (decreases alertness, promotes sleep) may play a role in why we sleep  Evolutionary/circadian sleep models – sleep’s main purpose is to increase a species’ chances of survival in relation to its environmental demands o Those who left shelter at night would be killed by nighttime predators o Circadian pattern developed as adaptation to environment  REM sleep is vital for mental functioning o Memory consolidation – ability to transform short-term memory into long-term memory  REM may strengthen neural circuits required for this process Sleep Disorders  Insomnia – chronic difficulty in falling asleep, staying asleep, or experiencing restful sleep o Most common sleep disorder o Caused by genetics, medical conditions, mental disorders, drugs, stress, poor lifestyle, and circadian disruptions  Narcolepsy – extreme daytime sleepiness and sudden, uncontrollable sleep attacks that may last from one minute to one hour o Narcoleptics may go right into REM sleep  REM Sleep Behaviour Disorder – loss of muscle tone that causes normal REM sleep paralysis is absent  Sleep Apnea – disorder characterized by a repeated cycle in which the sleeper stops breathing, momentarily awakens, and then returns to sleep o Caused by an obstruction in the upper airways  Sleepwalking – typically occurs during stage 3 or 4 sleep  Nightmares – frightening dreams that occur often during REM sleep in the hours prior to awakening  Night Terrors – sleeper suddenly sits up and screams o No recollection of the episode in the morning o Most common during stage 3 or 4 sleep The Nature of Dreams  Dreams most common when brain is most active (brain activity highest during REM sleep, and during final hours of sleep)  Freud’s psychoanalytic theory o Main purpose of dreaming is wish fulfillment (gratification of unconscious desires and needs)  Desires are too unacceptable to be consciously acknowledged and fulfilled in real life o Manifest content – story the dreamer reports o Latent content – the disguised psychological meaning o Dream work is the process by which the latent content is transformed into the manifest content  Activation-synthesis theory o During REM sleep, the brain bombards higher brain centers with random neural activity (activation) o Cortex attempts to interpret activity by creating a best fit to the pattern of activation (synthesis) o Accounts for the bizarreness of dreams  Cognitive approaches o Problem-solving dream models – dreams can help us find creative solutions to our problems and conflicts because they aren’t constrained by reality o Cognitive-process dream theories – focus on the process of how we dream  Propose that dreaming and waking thought are produced by same brain systems  Dreaming requires imagery skills and other cognitive abilities that young children have not yet developed  Explains why ability to dream develops with age  Similar activity between dreaming and waking mental activity  Rapid content shifts due to change of thought Daydreams and Waking Fantasies  Involved greater visual imagery than other forms of waking mental activity  Less vivid, emotional, and bizarre than nighttime dreams Drugs and Altered Consciousness Drugs and the Brain  Drugs can pass through the blood-brain barrier and alter consciousness by facilitating or inhabiting synaptic transmission  Agonist – drug that increases that activity of a neurotransmitter o Activates receptor, enhances production/storage/release, prevents reuptake. o Examples:  Opiates (pain relievers) – activate endorphin receptors  Amphetamines (stimulants) – enhance production and prevent reuptake of dopamine and norepinephrine  Antagonist – drug that inhibits or decreases the activity of neurotransmitters o Many bind to receptors, but do not affect neuron Tolerance and Withdrawal  Tolerance – the decreasing responsivity to a drug o Larger doses required to reach same effects o Stems from body’s attempt to maintain a state of optimal physiological balance (homeostasis) o Brain produces compensatory reactions to oppose effects of drug (e.g. decrease heart rate)  Withdrawal – occurrence of compensatory responses after drug use is discontinued, causing the person to experience physiological reactions opposite to those that had been produced by the drug Learning, Drug Tolerance, and Overdose  Tolerance for drugs partly depends on the familiarity of the drug setting o Continued drug use in same setting causes progressively stronger compensatory responses, increasing the tolerance o Classically conditions drug users to have compensatory responses while in drug setting, causing withdrawal, and increasing craving for drug  If drug user takes typical high dose in unfamiliar setting, compensatory responses don’t respond as strongly  leads to overdose Facts about Drug Addiction and Dependence  Drug tolerance does not always lead to significant withdrawal at typical doses  Substance dependence can occur even without tolerance or withdrawal  Physiological dependence is not the major cause of drug addiction Depressants  Decrease nervous system activity  Alcohol – most widely used recreational drug in numerous countries o Increases activity of gamma-aminobutyric acid (GABA) o Alcohol myopia – shortsightedness in thinking caused by inability to pay attention  Barbiturates (sleeping pills) and Tranquilizers (anti-anxiety drugs) – used as sedatives and relaxants o Depress the nervous system by increasing activity of inhibitory neurotransmitters Stimulants  Increase neural firing and arouse the nervous system  Amphetamines – increase dopamine and norepinephrine activity o Amphetamine psychosis – schizophrenia-like hallucinations and delusions that occur when the brain’s dopamine activity is artificially increased far beyond normal levels by heavy amphetamine use o Ecstasy primarily alters serotonin functioning by causing release and blocking reuptake of it  Cocaine – increases activity of norepinephrine and dopamine by blocking reuptake Other Drugs  Opiates (morphine, cod
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