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Psychology Textbook Notes - Chapter 3 & 4.docx

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McGill University
PSYC 100
Jens C Pruessner

Chapter 3  How does the Nervous system operate? o Intro:  Responsible for everything we think, feel, and do  Basic components:  Neurons: basic units of nervous system; cells that receive, integrate, and transmit info. Operate through electrical impulses, communicate with other neurons through chemical signals, and form neural networks.  Central nervous system (CNS): brain and spinal cord  Peripheral nervous system (PNS) all other nerve cells in the body o Neurons are specialized for communication  Nerve cells are powered by electrical impulses; communicate with other nerve cells through chemical signals  Three basic phases:  Reception: chemical signals are received from neighboring neurons  Integration: incoming signals are assessed  Transmission: signals are passed on to other neurons. o Types of Neurons:  Sensory (afferent) neurons: detect info from the physical world and pass that info along to the brain  Somatosensory nerves provide info from the skin and muscles  Motor (efferent) neurons: direct muscles to contract or to relax  Interneurons: communicate within local or short-distance circuits. o Neuron Structure:  4 structural regions:  Dendrite: detects chemical signals from neighboring neurons  Cell body (soma): collects and integrated info  Axon: transmits electrical impulses  Terminal buttons: bulbous end of an axon  Synapse: supports chemical communication between neurons  Synaptic cleft: narrow gap btwn terminal button (presynaptic membrane) and dendrite (postsynaptic membrane) of neighboring neuron  Myelin sheath: encases and insulates axons  Composed of glial cells  Nodes of Raniver: spaces between glial cells. o Resting membrane potential is negatively charged:  Resting membrane potential: ratio of negative to positive ions is greater inside the neuron than outside  Polarized: when a neuron has more negative ions inside than out  Polarization: creates the electrical energy necessary to power the firing of the neuron o The roles of Sodium and Potassium Ions  Sodium ions and potassium ions contribute to a neuron’s resting membrane potential  Ions pass through the cell membrane channels  Flow of ions through each channel is controlled by a gating mechanism  Sodium-potassium pump: increases potassium and decreases sodium inside the neuron o Action Potentials cause neural communication  Action potential: neural impulse that passes along the axon and subsequently causes the release of chemicals from the terminal buttons. o Changes in electrical potential lead to action  Dendrites receive chemical signals.  Excitatory: depolarize cell membrane – increases likelihood of neuron firing  Inhibitory: hyperpolarize the cell membrane – decreases likelihood of neuron firing  These signals tell neuron whether to fire by affecting polarization  When neurons fire, the inside becomes more positively charged than the outside  After firing, the inside of the neuron returns to its slightly negative resting state. o Action potentials spread along the axon  Propagation: When the neuron fires, the cell membrane’s depolarization moves along the axon like a wave  Sodium ions rush through their ion channels, causing adjacent sodium channels to open  The action potential always moves down the axon away from the cell body to the terminal buttons  Whole process takes about 1/1000 of a second. o All or None Principle:  Neurons are barraged with thousands of excitatory and inhibitory signals, and its firing is determined by the number and frequency of those signals.  All-or-none Principle: a neuron fires with same potency each time, and although frequency can vary, a neuron either fires or doesn’t – it cannot partially fire. o Neurotransmitters Bind to receptors across the synapse  Neurons are separated by the synaptic cleft  Action potentials cause neurons to release chemicals from terminal buttons. The chemicals travel across the synaptic cleft and are received by other neurons’ dendrites.  Presynaptic neuron: The neuron that sends the signal  Postsynaptic neuron: the neuron that receives the signal  Inside each terminal button are vesicles containing neurotransmitters  Neurotransmitters: chemical substances carrying signals from one neuron to another.  Receptors: specialized protein molecules on the postsynaptic membrane; neurotransmitters bind to these molecules after passing the synaptic cleft. o Neurotransmitters bind with specific receptors  60+ chemicals convey info in the nervous system  Neurotransmitters stimulate specific receptors and block new signals until terminated  The effects (excitatory/inhibitory) of a neurotransmitter are a function of the receptors that the neurotransmitters bind to  Events that terminate the neurotransmitter’s influence in the synaptic cleft are:  Reuptake: Neurotransmitter is reabsorbed into the presynaptic terminal buttons  Enzyme deactivation: Enzyme destroys the neurotransmitter  Autoreception: signal the presynaptic neuron to stop releasing the neurotransmitter o Neurotransmitters influence mental activity and behavior  Drugs and toxins alter a neurotransmitter’s actions in three ways:  1: alter how it is synthesized  2: raise or lower amount of neurotransmitter released from terminal buttons  3: by blocking reuptake, changing the way neurotransmitter is deactivated in synaptic cleft, and affect the concentration of the neurotransmitter.  Agonists: drugs enhancing actions of neurotransmitters  Antagonists: drugs inhibiting actions of neurotransmitters o Types of neurotransmitters:  9 Types: 1) Acetylcholine (Ach): Motor control over muscles, and learning, memory, sleeping, and dreaming 2) Epinephrine: Energy 3) Norepinephrine: Arousal and vigilance 4) Serotonin: Emotional states and impulsiveness, and dreaming 5) Dopamine: Reward and motivation, Motor control over voluntary movement a. Depletion is implicated in PARKINSON’S DISEASE (PD), discovered in 1917 6) GABA (gamma-aminobutyric acid): inhibition of action potentials, anxiety reduction, and intoxication (through alcohol) a. People with low GABA use Valium, and alcohol 7) Glutamate: Enhancement of action potentials, learning and memory 8) Endorphins: pain reduction, reward 9) Substance P: Pain perception, mood and anxiety.  Monoamines: Regulate arousal, feelings, and motivate behavior.  Epinephrine, norepinephrine, serotonin, and dopamine  Deep Brain Stimulation: 1987  Surgical implantation of electrodes deep within the brain and using mild electrical stimulation in the regions affected by the disorder, similar to a pacemaker for the heart.  What are the basic brain structures and their functions? o Intro  Adult human brain weighs 3 lbs / 1.4 kgs  It is a collection of interacting neural circuits accumulated and developed throughout human evolution.  Has evolved mechanisms to regulate breathing, food intake, sexual behavior, body fluids, as well as sensory systems to aid in navigation and assisting in recognizing friend and foe.  Franz Gal and Johann Spurzheim proposed Phrenology:  Idea that brain operates through functional localization  Karl Lashley built his research on idea of Equipotentiality  Specific brain regions were involved in motor control and sensory experiences, whereas all other parts contributed equally to mental abilities.  DISCREDITED. o Brain consists of patchwork of highly specialized areas  Paul Broca:  1961 autopsy on Monsieur Leborgne. Discovered: o Broca’s Area: small portion of left frontal region of the brain crucial to production of language. o The Brain Stem Houses the Basic Programs of Survival  Spinal cord is a rope of neural tissue  Runs inside hollows of vertebrae  Pelvis to skull base  Functions:  Coordination of reflexes  Carry sensory info up to the brain and motor signals from the brain to body parts below to initiate action.  Composed of two tissue types:  Gray matter: dominated by neuron’ cell bodies  White matter: consists of axons and fatty sheaths surrounding them o Gray and White matter is seen in the brain too  Brain Stem: extension of spinal chord housing structures controlling functions associated with survival such as breathing, swallowing, vomiting, urination, and orgasm  Consists of:  Medulla oblongata  Pons  Midbrain  Contains:  Neuron of network known as the reticular formation o Projects up into cerebral cortex, affecting general alertness, and inducing and terminating sleep stages. o Cerebellum is essential for movement  Cerebellum: located at back of brain, below the cerebral cortex and behind the brain stem  Important for motor function properly  Motor learning and motor memory  Involved in the experience of empathy o Subcortical Structures Control Emotions and Appetitive behaviors  Forebrain: above cerebellum and brain stem  Consists of the two cerebral hemispheres  Cerebral cortex  Subcortical regions: lie under the cortex  Subcortical structures:  Hypothalamus o Regulates body function  Thalamus o Sensory gateway  Hippocampus o Memory  Amygdala o Emotion  Basal ganglia o Movement o Reward  Limbic system: border between evolutionarily older parts of the brain (stem and cerebellum) and newer parts (cerebral cortex)  Control appetite behaviors and emotions o Hypothalamus:  Hypothalamus: involved in regulation of bodily functions including body temperature, blood pressure, and blood glucose levels, Also influences basic motivated behaviors  Thirst, hunger, aggression, lust  Located above roof of mouth. o Thalamus:  Thalamus: gateway to brain. Receives almost all incoming sensory info before that info reaches the cortex.  All senses except smell o Hippocampus and Amygdala:  Hippocampus: associated with the formation/storage of memories  Creates new interconnections within the cerebral cortex with each new experience  Grows larger with increased use o London Taxi Driver Study  Amygdala: serves a vital role in learning to associate things with emotional responses and processing emotional info.  Located in front of the hippocampus  Intensifies function of memory during times of emotional arousal o Frightening experience can be (inaccurately) seared into your memory for life  Developed over evolution to protect animals from danger  2004: Hamman and colleagues found activity increases when people view sexually arousing stimuli o The Basal Ganglia:  Basal Ganglia: system of subcortical structures important for production of planned movement  Receives info from entire cerebral cortex  Project that input to the motor centres of the brain stem  Via Thalamus, they also project the input back to the motor planning area of the cerebral cortex  Nucleus Accumbens: important for experiencing reward and motivating behavior. o Cerebral cortex underlies complex mental activity  Cerebral cortex: outer layer of brain tissue, which forms the convoluted surface of the brain.  Site of all thoughts, detailed perceptions, and complex behaviors  Allows us to comprehend selves, others, and outside world  2 hemispheres  4 lobes EACH(?) o Occipital parietal temporal and frontal.  Corpus callosum: o Massive bridge of millions of axons connecting hemispheres and allowing info to flow between them  Occipital lobes: regions of cerebral cortex at the back of the brain important for vision  Primary visual cortex: major destination for visual info  Parietal lobes: regions of cerebral cortex in front of occipital and behind frontal lobes important for sense of touch and conceptualizing special layout of an environment  Info is directed to primary somatosensory cortex o Strip in front part of lobe running from top of brain down the sides o Groups nearby sensations: sensations on fingers are near sensations on the palm… o Covering the primary somatosensory area is a distorted representation of the entire body: the somatosensory homunculus. o Homunculus is based on mappings by neuro- researcher Wilder Penfield  Temporal Lobe: regions of cerebral cortex below the parietal lobes and in front of occipital lobes important for processing auditory information, for memory, and for object and face perception  Holds the primary auditory cortex responsible for hearing  Fusiform face area  Frontal Lobes: regions of cerebral cortex at the front of the brain important for movement and higher-level psychological processes associated with prefrontal cortex  Primary motor cortex includes neurons projecting onto the spinal cord and moving body’s muscles.  Prefrontal Cortex: frontmost portion of the frontal lobes, especially prominent in humans; important for attention, working memory, decision making, appropriate social behavior, and personality  Occupies 30% of human brain  What makes humans unique o Prefrontal Cortex in Close-Up  Phineas Gage:  In 1848 he was 25, and got into an accident  Rod through his prefrontal cortex  Led to personality changes.  He “was no longer Gage”  Had epileptic seizures 12 years later and died in months  Some areas of the brain in fact have specific functions  Prefrontal cortex (area destroyed for Gage) is concerned with social phenomena (that Gage lost the ability to carry out)  Lobotomy: deliberate damaging of the prefrontal cortex to subdue mental patients  How does the brain communicate with the body? o Intro:  Peripheral nervous system transmits a variety of info to the CNS.  It responds to messages from the CNS to perform specific behaviors or make bodily adjustments  Both systems interact with a different mode of communication within the body: the endocrine system o The Peripheral Nervous System includes the somatic and autonomic systems  Two Components of the PNS:  Somatic Nervous System: a component of the peripheral nervous system that transmits sensory signals and motor signals between the CNS and the skin, muscles, and joints  Autonomic Nervous System (ANS): A component of the PNS that transmits sensory signals and motor signals between the CNS and the body’s glands and internal organs o Sympathetic and parasympathetic divisions:  2 types of signals travel from CNS to organs and glands, controlling their activity:  Sympathetic division: division of the autonomic nervous system that prepares the body for action  Parasympathetic division: division of the autonomic nervous system that returns the body to its resting state o The endocrine system communicates through hormones  Endocrine system: a communication system that uses hormones to influence thoughts, behaviors, and actions  Brain receives info from the nervous system about potential threats to the organism. The brain communicates with the endocrine system to prepare to deal with those threats  Main diff btwn nervous and endocrine systems:  Modes of communication. o Nervous system: electrochemical signals o Endocrine system: hormones  Hormones: chemical substances, released from endocrine glands, that travel through bloodstream to targeted tissues; the tissues are subsequently influenced by the hormones o Hormones’ effects on sexual behavior  Gonads: main endocrine glands involved in sexual behavior: in males, the testes; in females, the ovaries.  The 2 major gonadal hormones are identical in males and females  What differs is the quantity: o Androgens – Testosterone – more prevalent in males o Estrogens – estradiol and progesterone – more prevalent in females  Women’s sexual activity is not particularly linked to the menstrual cycle  But, ovulating women find masculine men more attractive o Actions of the Nervous system and endocrine system are coordinated  Communications systems link neurochemical and physiological processes to behaviors, thoughts, and feelings  Endocrine system is under the CNS’s control  Brain interprets external and internal stimuli, then sends signals to the endocrine system, which responds by initiating various effects on the body and on behavior  Most of central control of endocrine system is accomplished by the hypothalamus  Pituitary Gland: a gland located at the base of the hypothalamus that sends hormonal signals to other endocrine glands, controlling their release of hormones  Neural activation causes the hypothalamus to secrete a particular releasing factor  The releasing factor causes the pituitary to release a hormone specific to that factor  The hormone travels through the bloodstream to endocrine sites throughout the body  Once the hormone reaches the target sites, it touches off the release of other hormones which then affect bodily reactions or behavior  Growth Hormone (GH): hormone released from pituitary gland prompting bone, cartilage, and muscle tissue to grow or helps them regenerate after injury  Growth hormone releasing factor (GRF): stimulates release of GH which relies on protein to build bones and muscles  What is the Genetic Basis of Psychological Science? o Intro:  Do genes determine our thoughts and behaviors? How do environmental influences, such as cultures we are raised in, alter how our brains develop and change?  Genetics: usually talks about characteristics like hair color, height, etc., but also refers to processes involving turning genes on or off.  Environment’s affects our genes o All of Human Development has a genetic basis  Within nearly every cell in the body is the genome for making the entire organism  Genome: master blueprint providing detailed instructions for everything from how to grow a gallbladder to where the nose goes on the face  Chromosomes: structures within cell body made up of deoxyribonucleic acid (DNA), which consists of genes.  DNA consists of two intertwined strands of molecules in a double helix shape  Every cell has 23 pairs  half from mother and half from father  Genes: units of heredity that help determine the characteristics of an organism  Each gene specifies and exact instruction to manufacture a distinct polypeptide.  One or more polypeptide makes up a protein  Proteins are the basic chemicals that make up the structure of cells and direct their activities  The environment determines which and when proteins are produced  Although each cell contains the same DNA, cells become specialized depending on which genes are expressed  Gene expression determines the body’s basic physical makeup, and specific developments throughout life  Human Genome Project: found that we have only from 20,000- 30,000 genes o Heredity involves passing along genes through reproduction  Mechanisms responsible for heredity were discovered by the monk Gregor Mendel C.1866  Selective breeding, strictly controlling which plants bred with other plants  Dominant gene: gene that is expressed in the offspring whenever it is present  Recessive gene: gene that is expressed only when it is matched with a similar gene from the other parent o Genotype and Phenotype:  Genotype: genetic constitution of an organism, determined at the moment of conception  Phenotype: observable physical characteristics resulting from both genetic and environmental influences  Genetics, or nature, is one of the two influences on phenotype  Phenylketonuria (PKU): unable to break down phenylalanine enzymes, and can lead to severe brain damage o Polygenic effects:  Polygenic: a trait that is influenced by many genes as well as by the environment  The rich variety of skin colors (phenotype) is not the end product of a single dominant/recessive gene pairing (genotype). It shows the effects of multiple genes. o Genotypic Variation is created by sexual reproduction  Females have two X chromosomes  Males have one X and one Y chromosome  Reproductive cells divide to produce gametes, the egg and sperm cells  Each gamete contains half of every chromosome pair  After one sperm and one egg combine during fertilization, the resulting fertilized egg, known as a zygote, contains 23 pairs of chromosomes.  Zygote grows through cell division, which has 2 stages:  First: chromosomes duplicate  Then, cell divides into two new cells with an identical chromosome structure  Cell division is the basis of the life cycle and is responsible for growth and development o Errors during cell division: lead to mutations o Can be adaptive or maladaptive o If advantageous/adaptive, it can spread through the gene pool. o Genes affect behavior:  Your abilities and psych traits are influenced by the interaction of your genes and the environment in which you were raised or to which you are now exposed  The study of how genes and environment interact to influence psych activity is known as behavioral genetics o Behavioral Genetics methods  Differences between siblings exist  Therefore, behavioral genetics use 2 methods to asses the degree to which traits are inherited:  Twin Studies: compares similarities between different types of twins to determine the genetic basis of specific traits  Adoption Studies: compares the similarities between biological relatives and adoptive relatives  Monozygotic twins: identical twins; twin siblings resulting from one zygote splitting in two and therefore sharing same genes  Dizygotic twins: fraternal twins; twin siblings resulting from two separately fertilized eggs and therefore are no more genetically similar than non-twin siblings  One way to conduct behavioral genetic study is to compare monozygotic twins who have been raised together with ones who were raised apart.  Minnesota Twin Project: twins, raised together or apart, are likely to be similar o Jim Twins (married and divorced and kids and dogs all same names) o Oskar Stohr and Jack Yufe (one a Nazi and one a Jew) o Understanding Heritability:  Heredity: transmission of characteristics from parents to offspring by means of genes  Heritability: statistical estimate of the extent to which variation in a trait within a population is due to genetic factors  Depends on variation: measure of overall diff among a group of people for a particular trait  Refers to populations, not individuals o Social and Environmental Contexts influence Genetic Expression  Nature and nurture together affect behavior  Nature and nurture are inextricable entwined  Genes predispose people to certain behaviors  Those behaviors prompt others to respond in particular ways  Together, the behaviors, the repsonses, and subsequent actions shape people’s phenotypes.  Because genes and social contexts interact, separating their independent effects is very difficult/impossible o Genetic Expression can be Modified  Researchers can enhance or reduce the expression of a particular gene or even to insert a gene from one animal species into the embryo of another  Knockouts: particular genes have been knocked out of the animal  Changing one gene’s expression leads to the expression of a series of other genes  Genes seldom work in isolation to influence mind and behavior  Complex interaction among thousands of genes give rise to the complexity of human experience  How Does the Brain Change? o Intro:  In a perfect illustration of how nurture can influence nature, the brain can reorganize itself based on which parts of it are used lightly and which are used heavily  Plasticity: property of the brain allowing it to change as a result of experience, drugs, or injury. o The interplay of Genes and Environment Wires the Brain  Gene expression is profoundly affected by environment  Which cells express which genes and to what extent, depends to a large extent on environment  Brain plasticity reflects the interactive nature of our biological and environmental influences o Cell identity becomes fixed over time  In developing embryo, each new cell receives signals from its surroundings determining what type of cell it will become  If cells from one part of an embryo are surgically transplanted onto another part, the transplant’s success depends on how well developed the cell’s identity is.  Tissue transplanted early enough completely transforms into whatever type is appropriate for its new location  As an embryo develops, each cell becomes more and more committed to its identity, so transplanting cells too late may disfigure the organism  Fetal cells are undeveloped to become any type of tissue, so they may be used to cure diseases o Experience fine tunes neural connections  Connections form between brain structures when growing axons are directed by certain chemicals that tell them where to go and where not to go.  Major connections are established by chemical messengers, but detailed connections are governed by experience.  Plasticity has critical periods  Particular experiences must occur for development to proceed normally during these periods  Experience is important for normal development and maybe even more so for superior development o Culture affects the brain  Cultural experiences shape how we view the world and how we think  Contribute to different patterns of brain activity  Cultural experience appears to fine-tune the brain’s responses to important environmental cues. o The brain rewires itself throughout life  Brain plasticity decreases with age  Into old age, the brain can still grow new connections among neurons and even grow new neurons.  Rewiring and growth within the brain represents the biological basis of learning o Change in the strength of connections underlies learning  Memories are reflected in the brain’s physical changes  Changes in the brain are most likely not in its larger wiring or general arrangement.  Changes are mainly in the strength of existing connections  When two neurons fire simultaneously, the synaptic connection between them strengthens.  Strengthened synaptic connection makes these neurons more likely to fire together in the future  Donald Hebb: (1940’s) “fire together, wire together” accounts for the “burning in” of an experience, and the ingraining of habits  Sometimes, entirely new connections grow between neurons  This is a major factor in the recovery from brain injury  New neurons are produced in some brain regions: neurogenesis  Occurs in the hippocampus  Social environment can strongly affect brain plasticity. Neurogenesis may underlie neural plasticity. o Changes in the brain  Functions of portions of the cerebral cortex shift in response to their activity  Phantom limb: when amputees still feel their amputated limb’s sensations and feelings. Can be recreated through touching the place closest on the body in the homunculus o The Puzzle of Synesthesia  Synesthesia: cross-sensory experience (e.g. a visual image has a taste).  Phantom limb is caused primarily by environment, but synesthesia is caused primarily by genetics o Females’ and Males’ brains are similar and different  Hormonal differences might affect brain development, and thus might influence the way males and females differ on some cognition tasks including ease with which they mentally rotate objects or recall parts of a story  Sex diffs in anatomy are referred to as sexual dimorphism  Males have larger brains generally, but larger does not necessarily mean better  Halves of women’s brains are connected by more neural fibers than men’s are  Corpus callosum connective tissue is larger in women o The brain can recover from injury  Following an injury in the cortex, the surrounding gray matter assumes the function of the damaged area  Such plasticity involves all levels of the CNS, from the cortex to the spinal chord  Radical hemispherectomy: surgical removal of an entire cerebral hemisphere for children paralyzed by epilepsy  Transplantation of human fetal tissue to repair damage  Transplanted tissue consists of stem cells  Master cells can regenerate themselves, and develop into any type of tissue (muscle or nerve cells, etc.)  Challenge is to get the newly introduced cells to make the proper connections so that the damaged circuits regrow. Chapter 4  How do we sense our worlds? o Intro:  Divide the way we experience the world into two distinct phases:  Sensation: the sense organs’ detection of external stimuli, their responses to the stimuli, and the transmission of these responses to the brain.  Perception: the processing, organization, and interpretation of sensory signals; it results in an internal representation of the stimulus.  What we sense is the result of how we perceive  Brain processes actively construct perceptual experiences from sensory experiences  Constant conversion of sensation to perception allows us to adapt to the details of our environments  They sometimes fill in info that the environment has not provided  Perception is based on prior experiences, which shape our expectations about new sensory experiences. o Stimuli must be coded to be understood by the brain  Sensory Coding: Sensory organs translate physical properties of stimuli into patterns of neural impulses  Brain cannot process physical stimuli directly, so stimuli must be translated into chemical and electrical signals the brain can interpret.  Transduction: process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation.  Sensory Receptors: specialized sense organ cells that receive physical or chemical stimulation and pass the resulting impulses to connecting neural impulses.  Most sensory info goes to thalamus  Neurons in the thalamus send info to the cortex, where incoming neural impulses are interpreted as sight, smell, sound, touch, or taste.  Each sense organ contains different types of receptor cells. Each type of receptor is designed to detect different types of stimulus energy  The brain needs qualitative and quantitative info about a stimulus o Regardless of color, quantitative info includes the brightness of light. o Identify qualitative differences because different sensory receptors respond to qualitatively different stimuli.  In contrast quantitative diffs in stimuli are coded by the rate of a particular neuron’s firing. o More rapid neuron firing is responding at higher frequency to a more intense stimulus  Course Coding: o Sensory qualities are coded by only a few different types of receptors o Psychophysics measures the relationship between stimuli and perception  Ernst Weber and Gustav Fechner  Examine our psychological experiences of physical stimuli. o Sensory thresholds:  Absolute threshold: minimum intensity of stimulation required prior to experiencing a sensation.  Stimulation intensity you would detect more often than by chance (+50%)  Difference threshold: the just noticeable difference between two stimuli  The minimum amount of change required for a person to detect a difference.  Weber’s Law: the just noticeable difference between two stimuli is based on a proportion of the original stimulus rather than on a fixed amount of difference. The more intense the stimulus, the bigger the change needed for you to notice o Signal Detection Theory:  Signal Detection Theory (SDT): perception theory based on idea that detection of a faint stimulus requires a judgment, not an all-or-none process  Any research on signal detection involves a series of trials in which a stimulus is presented in only some trials.  Stimulus Present: o Detected: hit o Undetected: miss  Stimulus absent: o Detected: false alarm o Undetected: correct rejection  Sensitivity to the signal is usually computed by comparing the hit rate with the false alarm rate  Response bias is the tendency to report detecting the signal in an ambiguous trial  Personal beliefs and expectations as well as the situation influence how a person experiences changes because they might require responses  Sensory Adaptation: a decrease in sensitivity to a constant level of stimulation  What are the Basic Sensory Processes o In taste, taste buds detect chemicals  Gustation: the sense of taste  To keep poisons out of our digestive systems while allowing good food in.  The stimuli for taste are chemical substances from food that dissolve in saliva  Taste Buds: sensory organs in the oral cavity containing the receptors for taste  Mostly on tongue, inside papillae  We have 8-10,000 taste buds
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