Psychology Reading Notes

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Psych 1 (part 1 of 2 textbook notes)

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Psychology Reading Notes: • Week 2 ◦ Hans the horse – teaches lesson on scientific attitude and methods ▪ owner: von Osten, psychologist who found the truth: Oskar Pfungst ▪ people saw what they expected to see ◦ terms: ▪ fact/observation – an objective statement usually based on direct observation ▪ theory – an idea or conceptual model designed to explain existing facts and make predictions about new facts that might be discovered ▪ hypothesis – predictions about new facts that is made from a theory ◦ value of... (in scientific experimentation) ▪ skeptism – logical foundation of scientific testing ▪ controlled experimentation – observations made in a controlled environment ▪ avoidance of a communication of expectation to subjects (observer-expectancy effects) ◦ Research Strategies: ▪ 3 dimensions to research study • research design – experiments, correlation studies, and descriptive studies ◦ experiments – procedure in which a researcher systematically manipulates one or more independent variables and looks for changes in one or more dependent variable while keeping all other variables constant ▪ independent and dependent variable ▪ subjects/participants ▪ within-subject experiments – each subject tested in each of the different conditions of the independent variable • can often be done with one subject ▪ between-groups experiments – separate group of subjects for each different condition of the independent variable ◦ correlation studies – study in which researcher does not manipulate any variable, but observes or measures two or more already existing variables to find the relationship between them ▪ doesn't tell us directly if change in one variable causes the change in another (cause-and-effect), due to the multitudes of different variables ◦ descriptive studies – aims to describe the behavior of an individual or set of them without assessing relationships between different variable • setting – place in which study is conducted: field or laboratory ◦ laboratory study – one in which subjects are brought to a specially designated area that has been set up to facilitate the researcher's collection of data or control over environmental conditions ▪ more control, more artificial ◦ field study – one where setting is not a laboratory (ex. People's home, mall, part of subject's real environment) ▪ less control, more natural behavior • data-collection method – self-report, observation ◦ self-report – people are asked to rate or describe their own behavior or mental state (ex. questionnaire, interview) ◦ observational – researchers observe and record the behavior of interest ▪ naturalistic observation – researcher aboids interfering with the subject's behavior ▪ tests – researcher deliberately presents problems, tasks, or situations to which subject responds



Week 3 ◦ Two Categories of Statistical Methods in Psychology ▪ descriptive statistics – helps summarize sets of data • includes all numerical means of summarizing a set of data ◦ mean, median can both represent the central tendency of a set of data ◦ variability – degree to which numbers in a set differ from one another and the mean ▪ commonly measured by standard deviation ◦ correlation coefficient – coefficient ranging from -1 to +1 that assesses strength and direction of the relationship between two variables ▪ strong/moderate “positive correlation” or “negative correlation” ▪ inferential statistics – used to assess likelihood that relationships observed are real and repeatable or due merely to chance • necessary due to chance being a major contributor to variability • statistical significance ◦ inferential statistical methods – procedures for calculating probability that the observed results could derive from chance alone ◦ p (level of significance) – the probability that a correlation coefficient as large or larger than that observed would occur by chance if, in the larger population, there were no difference between the two means ▪ things labeled as “statistically significant” if the value of p is less than 5% (or less) ▪ components of calculation • size of the observed effect • number of individual subjects or observatios • variability of the data within each group – comparing group means, index of variabilities. ◦ Variability can be thought of as an index of the degree to which chance factors influence a set of data. (ex. Greater variability in depression within a treatment group indicates a greater randomness attributable to chance) ◦ Error and Bias ▪ error – random variability in results, not a big problem as it tends to even out with averages ▪ bias – nonrandom (directed) effects caused by some factor(s) extraneous to the research hypothesis • big problem due to inability of statistical techniques to identify or correct it → may lead to wrong conclusion • 3 types: sampling bias, measurement bias, and expectancy bias ◦ sampling bias - has to do with the way individuals are selected, in which members of a certain group are initially different from those of another group or of the larger general population ◦ measurement bias ▪ reliability of measurement – getting consistent measurements not greatly affected in a random manner by the tools or subject ▪ validity of measurement – when measurement procedure measures or predicts what it's meant to measure or predict. • when a procedure has “face validity” it means that common sense tells us that the procedure assesses the intended characteristics • a more certain way to gauge validity of measuremnt is to correlate its scores with another, more direct index of the characteristic we want to measure ◦ criterion – the more direct index ◦ criterion validity ◦ expectancy bias ▪ observer-expectancy effects – when a researcher conveys a desire / expectation of a subject to act a certain way and thereby influences the subject • facilitated communication ◦ autism – congenital (present at birth) disorder of development, charaterized by a deficit in the ability to form emotional bonds and to communicate with other ▪ facilitators were actually the ones typing the message • best way to prevent it is to keep the observer blind (uninformed) about the aspects of the study that might bias him or her ▪ subject-expectancy effects







a subject's expectation more than the experiment may account for what is observed to avoid, subjects should also be kept blind about aspects that might affect them, such as the treatment that they are getting • placebo – an inactive substance that looks like a drug ▪ double blind experiment – both observer and subject are blind Evolution by Natural Selection ▪ natural selection - selective breeding occurring in nature • dictated by the obstacles to reproduction imposed by the natural environment (predators, food supply, temperature, etc) • as a result, species vary in the number of offspring they produce – as long as inheritable differences that affect survival and reproduction exist, evolution will occur • not a moral force • can only lead to changes that are immediately adaptive, not ones that anticipate future needs ▪ 2 main sources of genetic variability: 1) reshuffling of genes 2) mutations • mutations: errors that occasionally and unpredictably occur during DNA replication ◦ ultimate source of all genetic variation ◦ usually more harmful than good, harmful ones weeded out by evolution • inheritance of acquired characteristics is NOT true ◦ originated by Jean-Baptiste de Lamarck ▪ environmental changes provide the force for natural selection • depending on the rate and nature of environmental change (as well as the degree to which genetic variability already exists), evolution may be fast, slow, or almost not at all ▪ evolution has no set route or planned end, nor can it prepare a species for some future purpose ▪ complex changes, requiring many mutations, require a long time to evolve Natural Selection as a Foundation for Functionalism ▪ functionalism: the attempt to explain behavior in terms of what it accomplishes for the behaving individual ▪ ultimate explanations: functional explanations at the evolutionary level. • States what the role of the behavior plays in an animal's survival and reproduction (i.e. how it helps pass the individual's genes to the next generation) ▪ proximate explanations: explanations dealing not with function but mechanism • states the immediate conditions both inside (physiology) and outside (stimuli) the animal that bring about the behavior ▪ all complex biological mechanisms underlying human behavior (including breathing, eating, and sex) and experience (including perception, learning, memory, thought, motivation, and emotion) are product of evolution by natural selection. ▪ 4 reasons why a particular trait/ behavior may not be useful: • trait is vestigial ◦ examples of vestigial characteristics include infants tightly grasping objects (especially hair) and our liking of sugar (which back long ago was a rare commodity) • trait is a side effect of natural selection for other traits ◦ example: the belly button which is a side effect of the umbilical cord • trait is simply a result of chance rather than selection- “genetic drift” ◦ example: people of different races tend o have different shaped noses • evolved mechanisms can't deal effectively with every situation ◦ example: our feeling of guilt aren't such that we can distinguish every possible condition and trigger guilt only when it's useful – it may still be triggered, even when triggering it is more harmful than helpful Natural Selection as a Foundation for understanding Species-Typical Behaviors ▪ species-typical behaviors – ways of behaving that characterize a species (a.k.a instincts) • ex. human facial expressions when showing emotion • learning affects species-typical behavior ◦ ex. though emotional expressions are species-typical, the cultural differences among them are learned ◦ two obvious examples include walking and the use of language ▪ though they are both species-typical behaviors, had a child grown up in an environment where either of them were impossible to practice, they wouldn't have been able to develop the capacities ◦ ex. birds wouldn't be able to sing their species-typical song without having heard it previously • •



biological preparedness is the basis of species-typical behavior ◦ ex. humans walking on two feet vs. a dog learning to walk on two feet – dogs can do it, but they aren't good at it ◦ it is relative rather than absolute – the behavior doesn't only stem from biological preparedness, it requires some sort of experience with the environment to develop ▪ two forms of cross-species comparisons (of behaviors): • homology: any similarity that exist because of the different species' common ancestry ◦ entail similarities in underlying construction & physiological mechanisms (i.e. neural & muscular mechanisms) ◦ useful for inferring the pathways along which species-typical behaviors evolve ◦ useful for research on the physiological mechanism of behaviors (i.e. how the brain and other biological structures operate to produce the studied behavior) • analogy: any similarity that stems from convergent evolution (which occurs when different species independently evolve common characteristics due to similarities in their habitats or lifestles) ◦ entail similarity in function and gross form, not in detail and underlying mechanism ◦ useful for inferring ultimate functions • example – using homologies as clues to find the possible evolutionary origins of (two) human smiles Evolutionary Analysis of Mating Patterns ▪ four broad classes of arrangements for sexual reproduction: • polygyny: one male mates with more than one female ◦ high female and low male parental investment ◦ generally, the more polygnous a species, the greater the average size difference is between the male and female ◦ usually occurs when the evolutionary advantage in mating with multiple partners is greater for males → males fight others to get the most mates • polyandry: one female mates with more than one male ◦ high male and low female investment ◦ found mostly in fishes and birds (egg-laying species) due to a smaller proportion of an egg layer's reproductive cycle being tied to the female body → eggs can be cared for by both parents ◦ females lay more eggs during a single breeding season than either she or she and one male can care for → best strategy is to leave eggs with the father who becomes the main or sole caretaker ◦ females are the more active and aggressive courters and have evolved to be larger, stronger, and in some cases more colorful than the males • monogamy: one male mates with one female ◦ equal investments by the two sexes ◦ due to neither sex being more likely than the other to fight over mates, there is little to no natural selection for sex differences in size and strength ◦ monogamy arises from the need for more than one adult to care for offspring ◦ 90+% of birds are predominately monogamous ◦ social monogamy (fathful pairing of mates for raising young) doesn't necessarily imply sexual monogamy (fidelity in copulation) • polygynandry: members of a group consist of more than one male and more than one female ◦ high investment in the gourp ◦ found in chimpanzees and bonobos ◦ evolved due to allowing a group of male and female adults to live together in relative harmony ◦ relative advantage (from female's perspective) is paternity confusion → the males wont kill the children as they don't know whether or not it's theirs, but instead protect and care for it (and the grou) as a whole ◦ bonobos unique in that sex appears to be a reducer of aggression than a cause of it ▪ Triber's theory of parental investment – in general, for species in which parental investment is unequal, the more parentally invested sex will be a) more vigorously competed for than the other and b) more discriminating than the other when choosing mates • relates courtship and mating patterns to sex differences in amount of parental investment • parental investment: the time, energy, and risk to survival that are involved in producing, feeding, and caring for each offspring – the loss, to the adult, of future reproductive capacity that results from production and nurturing of offspring ▪ Humans •





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largely monogamous, partly polygynous females have only a slight more parental investment, which follows with the general state of our mating patterns • human size differences exist, but not to the scale of such polygynous animals as seals • emotions that predispose us for mating bonds: romantic love and sexual jealousy ◦ also exists in monogamous birds (analogies, Xhomologies), but not in chimps – due to nature of parental care Evolutionary Analysis of Hurting and Helping • Aggression – fighting and threats of fighting among members of the same species ◦ brain mechanisms that motivate and organize such behavior have evolved because they help animals acquire and retain resources needed to survive and reproduce ◦ some reasons for why males are so aggressive: status and sex, they want more of both ◦ bonobos are an exception (to chimps and humans) – they tend to be less aggressive overall, and females generally dominate males despite the males being physically larger and stronger ▪ females dominate due to forming strong alliances and helping one another • Helping: any behavior that increases the survival chance or reproductive capacity of another individual ▪ cooperation – occurs when an individual helps another while helping itself ▪ altruism – when an individual helps another, decreasing its own survival chance or reproductive capacity • 2 broad theories to explain altruism: ◦ kin selection theory – behavior that seems altruistic came about because it preferentially helps close relatives who are genetically most similar to the helper ▪ any gene that promotes the production and preservation of copies of itself can be a fit gene, from the point of view of natural selection, even if it reduces the survival chances of a particular carrier of the gene ◦ reciprocity theory – explains how acts of apparent altruism can arise even among non-kin as a form of long-term cooperation ▪ such a tendency can evolve if it is tempered by a species a) ability to remember debt and b) tendency to refrain from helping again someone who failed to reciprocate such help in the past Two Fallacies to avoid regarding evolution • Naturalistic Fallacy - believing natural selection favors the “moral” and “right” ◦ often indulged in by Social Darwinists who believe what is natural is what is right – Darwin did NOT fall for it • Deterministic Fallacy – the assumption that genetic influences on our behavior take the form of genetic control of our behavior which we can do nothing about ◦ genes do NOT directly influence behavior, but rather work in conjunction with the environment unconscious nature of ultimate functions – we us the proximate causation of our behaivor to explain what we do. We normally are unaware of the ultimate functions of our actions evolutionary perpective provides the boradest view we can take in psychology • it's concerned with the origins and ultimate functions of all aspects of human nature • all our mechanisms are biased toward generating behaviors that promote survival and reproductio • •



Week 4 ◦ Learning – any process through which experience at one time can alter an individual's behavior at a future time ▪ experience – any effects of the environment that are mediated by the individual's sensory systems ◦ Classical Conditioning: Fundamentals ▪ classical conditioning – a learning process that creates new reflexes • reflex – a simple, relatively automatic, stimulus-response sequence mediated by the nervous system ◦ to be considered a reflex, the response to a stimulus must be mediated by the nervous system ◦ because reflexes are mediated by the nervous system, they can be modified by experience • habituation – decline in the magnitude of a reflexive response when the stimulus is repeated several times in succession ◦ doesn't produce a new stimulus-response sequence but weakens an already existing one • conditioned reflex: new reflex (dependent on the unique conditions [conditioned stimulus] present in prior experiences) ◦ conditioned response: response to the conditioned stimulus • unconditioned reflex: the original reflex (with unconditioned stimulus and unconditioned response) • classical conditions is a form of reflex learning – it DOES produce a new stimulus-response sequence • sometimes called Pavlovian conditioning ▪ Pavlov discovered classical conditioning (from his earlier studies of digestive reflexes in dogs ▪ extinction: phenomenon in which a conditioned reflex is extinguished due to conditioned stimulus no longer leading to the expected result (unconditioned stimulus) → conditioned response lessens until it disappears ▪ conditioning and extinction involve different sets of neurons – one promoting the conditioned response, the other inhibiting ▪ spontaneous recovery: when a conditioned reflex is partially renewed due to the mere passage of time • shows that conditioned reflex is not unlearned in extinction but merely suppressed ▪ generalization: phenomenon in which new stimuli that resembled the conditioned stimulus triggers the conditioned response • in humans, it is found that generalization doesn't only occur when two stimuli are physically similar, but also when their subjective meanings are similar to the person – generalization can be used as an index of subjective similarity ◦ ex. words (style, freeze, ...) paired with lemon juice → “fashion”, “chill” caused more salivation than “stile”, “frieze” - showing conditioned stimuli to be not the physical sight or sounds of the words but the subject's interpretation of them ▪ discrimination training: procedure where generalization between two stimuli is abolished (enforce one, extinguish the other) • useful in studying sensory abilities and concept information ◦ Classical Conditioning: Beyond the Fundamentals ▪ Behaviorism • argued that science should avoid terms that refer to mental entities and should focus on relationship of S-R • Watson was the principal founder • believed that classical conditioning created a new S-R relationship ◦ didn't like the S-S theory due to it referring to an unobserved event in the mind ▪ Pavlov believed that classical conditioning resulted in a conditioned stimulus being associated to the unconditioned stimulus which triggered the response (S-S theory) • S-S thoery is more cognitive than S-R theory ▪ cognitive theories: theories in which hypothesized, unobserved entities within the mind are used to explain and predict behavior ▪ expectancy theory – states that all responses to the conditioned stimulus occur not because they were elicited by the unconditioned stimulus, but because of the subject's expectation (of a resulting unconditioned stimulus) ▪ conditioning depends on the predictive value of the conditioned stimulus • conditioned stimulus must precede the unconditioned stimulus – gives the stimulus value as a predictor • conditioned stimulus must signal heightened probability of occurrence of the unconditioned stimulus • conditioning is ineffective when an animal already has a good predictor (blocking effect) ▪ from a functional, evolutionary perspective, classical conditioning is a process by which individuals learn to prepare themselves, reflexively, for biologically significant events about to happen ▪ bodily reactions associate with natural emotions (fear [little Albert], hunger) and drives (sexual drives) can be conditioned



bodily reactions to drugs can also be conditioned usually, only the compensatory reaction to drugs (body's natural reaction meant to counteract the direct effect in order to restore the normal body state) become conditioned (not the direct effect of drugs) • reason: only responses that occur in a reflexive manner involving the central nervous system can be conditioned ▪ drug tolerance – the decline in physiological and behavioral effects that occur with some drugs when taken repeatedly • results in some people increasing their doses over time • partially due to conditioning (as well as long-term build up of physiological systems that help counteract the drugs) – conditioned compensatory reaction occurs before drug is taken → counteracts the direct effect ◦ doesn't work if drug is taken in a non-usual drug-taking environment ▪ conditioned reactions can cause drug relapse – after treatment to get over the initial withdrawal symptoms, when met with cues associated to drug use, the people experience the compensatory drug reactions which feel like withdrawal symptoms → elicits strongly felt need for the drug Operant Conditioning: Fundamentals ▪ operant responses or instrumental response: actions that operate on the world to produce some effect ▪ operant conditioning or instrumental conditioning: process by which people learn to make operant responses • ex. Thorndike's puzzle-box procedure ◦ law of effect: responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation, and responses that produce a discomforting effect become less likely to occur again in that situation ▪ formulated by Thorndike, but popularized by Skinner • “Skinner box” - nice in that the animal remains in the box and is free to respond (ex. pressing a lever for food) again with no constraints on when it may or may not respond ◦ reinforcer – a stimulus change that ollows a response and increases the subsequent frequency of that response ▪ ex. food (when lever pressed) or opening of cage (when latch pulled) ◦ conditioned reinforcer – stimuli that have reinforcing balue only because of previous learning ▪ ex. money - people act in ways to get more of it, only after learning what it can do/buy ▪ Skinner believed in operant conditioning without awareness • due to being a behaviorist, awareness of what we want (a mental phenomenon) wasn't a useful explanation for response ▪ Shaping • operant responses can only be reinforced after a response is actually performed...solution to problem: shaping • shaping: technique in which successively closer approximations to the desired response are reinforced until the desired response finally occurs and can be reinforced ▪ operant responses can also go through extinction and spontaneous recovery ▪ partial reinforcement: when a particular response only sometimes produces a reinforcer (in between continuous reinforcement and extinction) • four basic types: ◦ fixed-ratio schedule – reinforcer occurs after every nth response ◦ variable-ratio schedule – average number of responses required for a reinforcement is set ▪ ex. variable ratio 5 schedule – reinforcement comes on average of every 5 responses, more or less ◦ fixed-interval schedule – similar with ratio, except in terms of time ◦ variable interval schedule • type of reinforcement can affect the response rate and resistance to extinction ▪ positive and negative reinforcement • reinforcement (in Skinnere's terms) is any process that increases the likelihood that a particular response will occur ◦ positive - when the arrival of some stimulus follows a response makes a response more likely to occur ◦ negative – when a removal of some stimulus following a response makes it more likely to occur ▪ punishment – the opposite of reinforcement, when the consequence of a response decreases the likelihood of recurrence • positive – arrival of a stimulus decreases likelihood of recurrence • negative – removal of a stimulus decreases likelihood of recurrence ▪ ▪









Skinner uses reinforcement and punishment to explain, doesn't go into “desired” or “undesired” (mentalistic terms) Operant Condtioning: What's is learned? ▪ Discrimination training – can make an operant response to a stimulus more specific • ex. making a rat press a lever for food only when a tone (discriminative stimulus) is on ◦ discriminative stimulus can be thought of as a cue signaling the availability of a reinforcer • generalization also occurs for discriminative stimulus ◦ ex. pidgeon pecking key when a tree (despite variation) is shown ▪ pidgeons found to base their responses on a concept (a rule for categorizing stimuli into groups) of trees ▪ Behaviorist's approach • operative conditioning entails the strengthening of a bond between the reinforced response and stimuli that are present just before the response is made ◦ in this view, reinforcer is involved in learning only insofar as it helps in the connection of the S-R ◦ other theorists argue though that not only S-R relationship learned but also S-S (discriminative stimuli and reinforcing stimulus) relationship and R-S ( response and reinforcing stimulus) relationship ▪ Means-End Expectancies – expectation that a particular response in a particular situation will have a particular effect • S-R: tone → lever press • Means-End Expectancy: tone → expectation that lever press will give food ▪ reward contrast effect – involves shifts in the response rate when the value of the reward changes • negative contrast effect: when subjects are shifted from a strong reinforcer to a weak reinforcer → sharp drop in response rate • positive contrast effect – just the opposite of negative • explained by assuming 1) individual has learned to expect a certain reward and 2) is able to compare actual reward with the expected one Overjustification effect – when rewards provide an unneeded extra justification for engaging in a behavior that was previously enjoyable, which are then removed causing for a decline in the behavior (lower than if there had been no reward) ▪ cognitive reasoning: person comes to regard the task as something done for the reward rather than for its own sake Learning ▪ learning drives include play and curiosity (the drive to explore) ▪ learning divided into two categories:learning to do (skill learning - play) & learning about (information learning – curiosity) ▪ exploration often mixed with a degree of fear and is elicited by novel stimuli • one purpose of exploration is to determine whether or not an unfamiliar object or place is safe • ex. rat in a maze ◦ Tolman argued that rewards affect what animals do more than what they learn (rats with reward and no reward) ▪ latent learning: learning that is not immediately demonstrated in the animal's behavior ▪ observational learning: learning by watching others Special Learning Abilities ▪ innate biases in fear-related learning – people are biologically predisposed to acquire fear of situations and objects that pose a threat • the little Albert experiment failed when done with wooden blocks rather than a rat ▪ imprinting in precocial birds – learning to identify one's mother • imprinting – phenomenon, which emphasizes a sudden apparently irreversible nature of the learning process involved ◦ certain characteristics of imprinting help to ensure that under normal conditions, the babies will learn to identigy and follow their own mothers ▪ critical period – the restricted time period in which imprinting can occur ▪ stimulus features also play a part – the chicks will choose to follow a moving object as long as it has characteristics typical of a mother bird ▪ place-learning abilities – ability for learning and remembering specific locations that have biological significance to them ▪



Origins of Attitudes and Methods of Persuasion ▪ Attitudes through Classical Conditioning: No Thought • classical conditioning = automatic attitude generator • example found in everyday life: advertisements – can cause us to have positive attitude to stuff (cars, cigars, etc) ▪ Attitudes through Heuristics: Superficial Thought • automatic process of using certain decision rules (heuristics) to evaluate information and develop attitudes • ex. of heuristics ◦ lots of numbers and big words → must be well documented ◦ message phrased in terms of values I believe in → its probably right ◦ famous or successful people → more likely to be correct ◦ most people believe this message → its probably true • we learn to use such rules, presumably, because they allow us to make useful judgements with minimalexpenditures of time and mental energy → rules become mental habits that we use implicitly ▪ Attitudes through Logical Analysis of the Message: Systematic Thought • elaboration likelihood model – theory of persuasion proposing that a major determinant of whether a message will be processed systematically (through logical analysis of the content) or superficially is the personal relevance of the message • people are “cognitive misers” - we reserve our elaborative reasoning powers for messages most relevant to us and rely on mental shortcuts to evaluate messages that seem less relevant



Week 5 ◦ Behavior is a product of the body's machinery – especially the nervous system which receives info about the body's internal and external environment, integrates the info, and then controls the body's movements. ◦ Hippocrates believed that the brain were the source of feelings, thoughts, and all else “psychological”, while many others believed the heart and blood to be due to them being more obviously dynamic ◦ Brain ▪ ~2% of a person's weight, but consumes ~20% of a person's metabolic energy ▪ most complex and compact computing machine ▪ contains ~100 billion nerve cells (neurons) and ~100 trillion points of communication between neurons (synapses) • constantly active, monitors our environment, creates our mental experiences, and controls our behaviors • the “magic” lies not in the individual neurons but of the organization of their multitudes ◦ Neuorns ▪ Nervous system is made up of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerve extensions extend out from the central nervous system ▪ neurons are NOT nerves • nerves: a bundle of many neurons' axons within the peripheral nervous system ◦ connects the central nervous system to the body's sensory organs, muscles, and glands ▪ vary in shapes and sizes and functions – but can be grouped into three categories based on their function and location: • sensory neurons ◦ they are bundled together into nerves ◦ carry info from sensory organs (eyes, ears, nose, tongue, skin) into the central nervous system • motor neurons ◦ bundled into nerves ◦ carry messages out from central nervous systems to operate muscles and glands • interneurons ◦ exist entirely within the central nervous systematicallycarry messages from one set of neurons to another ◦ collect, organize, and integrate messages – they make sense of the input from other neurons, generate our mental experiences, and initiate and coordinate all our behavioral actions through their connections to motor neurons ◦ outnumber the other two types - ~100 billion interneurons to the few million sensory and motor









neurons basic parts: • cell body - contains the cell nucleus and other basic machinery common to all bodily cells, widest part of the neuron • dendrites - receives input to the neuron ◦ thin tube-like extensions that branch out extensively ◦ motor neurons and interneurons – dendrites extend direct off the cell body and branch of near the cell body ▪ dendrites increase the surface area of the cell and therby allow for receopt of signals from other neurons ◦ sensory neurons – dendrites extend from one end of the axon and into a sensory organ ▪ respond to sensory signals (ex. Sound waves in the ear, or touch on the skin) • axon - carries messages to other neurons (or muscle cells, in the case of motor neurons) ◦ thin tube-like extension from the cell body (can be very long, extending from a person's big toe to their brain) ◦ axons usually form branches some distance away from the cell body ending with a small swelling (axon terminal) ▪ axon terminals release chemical transmitter molecules onto other neurons (or onto muscle cells or glandular cells, in the case of motor neurons) ◦ myelin sheath – a casing sometimes surrounding the axon ▪ formed from special non-neural cells ▪ helps speed up the movement of neural impulses along the axom ▪ not part of the neuron – it's formed of separate glial cells action potentials – all-or-none impulses fired off by neurons • motor neurons and interneurons – impulses triggered at the junction between the cell body and the axon • sensory neurons – impulses triggered at the dendritic end of the axon and travel through the cell body to the axon • don't occur in different sizes or gradations – they either occur or they don't (all-or-none) • each action potential produced is the same strength as any other action potential produced by that neuron and it retains its full strength all the way down the axon • to convey different degrees of intensity, it varies its rate of producing action potentials which varies the strength of its effect on other neurons or muscle cells Resting Neurons have a constant electrical charge across its membrane • cell membrane – a porous “skin” that encloses each neuron and permits certain chemicals to flow in and out of the cell • intracellular fluid – a solution of water and dissolved chemicals inside the neuron ◦ soluble protein molecules (A-) exist only in the intracellular fluid ◦ potassium ions (K+) are more concentrated in the intracellular fluid than extracellular • extracellular fluid – solution of water and dissolved chemicals outside the neuron ◦ sodium ions (Na+) and chloride ions (Cl-) are both more concentrated in the extracellular than the intracellular • more negatively charged inside than out due to K+ ions diffusing out → imbalance of charges across the membrane ~ -70 mV (resting potential) relative to outside ◦ resting potential is the source of electrical energy that makes action potentials possible action potentials are derived from a brief change in membrane permeability (i.e.channels open up to allow sodium ions to pass through) – its a wave of change in the electrical charge across the axon membrane • two forces tend to drive Na+ into the cell when the channels open: 1) concentration force which exist due to more Na+ existing outside the cell than inside 2) electrical force which exists because like charges repel each other → positive environment outside the cell pushes the positive Na+ inward • result: electrical charge across the membrane reverses itslf and becomes momentarily positive – the depolarization phase of the action potential • depolarization → channels allowing Na+ to pass through closes while those allowing K+ to pass remain open → K+ driven out by the same forces → repolarization phase of action potentially • sodium-potassium pump – chmeical mechanism contained in the membrane, continuously moves Na+ out and K+ in • threshold: critical value which, when reached, causes the sodium channels to open, triggering an action potential



action potential regenerates itself from point to point along the axon - once an action potential occurs, it depolarizes the area, causing the channels to open, triggering another action potential • speed at which action potential moves down the axon is affected by the axon's diameter and myelin sheath ◦ larger the diameter → less resistance to spread of electric currents → conducts action potentials faster ◦ sheath insulates theaxon's membrane → ions can mobe through it only at spaces (nodes) between adjacent cells → action potential skips down axon from one node to the next, faster than it could move as a continuous wave Synaptic Transmission ▪ synapse – the junction between each axon terminal and the cell body or dendrite of the receiving neuron ▪ (neuro)transmitter – chemical substance released by the axon terminal when it's reached by an action potential → alters receiving neuron in ways that influence its production of action potentials ▪ synaptic cleft – very narrow gap that separates the axon terminal from the membrane of the influenced cell ▪ presynaptic membrane – membrane of the axon terminal ▪ postsynaptic membraane – membrane of the cell ▪ vesicles – tiny globe-like things within the axon terminal that contain thousands of molecules of chemical neurotransmitter • when it releases the neurotransmitters, they diffuce through the fluid in the cleft and some attach to special receptors on the postsynaptic membrane → opens up the channel ▪ two basic types of synapses • fast synapses – quickly excite or inhibit postsynaptic neuorns ◦ if postsynaptic cell is a muscle cell, flow of ions triggers a biochemical process that causes cell to contract ◦ if postsynaptic cell is a neuron, the result is a change in the polarization of the neuron, the direction of which depends on whether the synapse is excitatory or inhibitory ▪ excitatory synapse – transmitter opens sodium channels → causes slight depolarization of the neuron → tends to increase the rate of action potentials triggered in the neuron ▪ inhibitory synapse – the transmitter opens chloride (Cl-) channels or potassium (K+) channels → causes slight hyperpolarization of the neuron → tends to decrease the rate of action potentials triggered in the neuron ◦ all fast synaptic transmitters are small molecules (with < 10 carbon atoms) – many of them are amino acids. ▪ Amino glutamate is the transmittter at most of the brain's excitory fast synapses ▪ GABA (gamma-aminobutyric acid) is the transmitter at most of the brain's inhibitory fast synapses ◦ rate of action potential in the postsynptic neuron's axon depends on the net effect of the polarizing influences • slow synapses – presynaptic neurons exert a wide variety of long-term effects on postsynaptc neurons ◦ slow neurotransmitters trigger sequences of biochemical events in postsynaptic neuron that take time to deleop and can alter the neuron's functioning for periods ranging from milliseconds to weeks or more - don't directly open ion channels ◦ there are many different types of slow-acting synapses that differ in their effects in the central nervous systme ▪ es. some do open ion channels (indirectly with a longer effect) ▪ neromodulators: transmitters that alter the cell in long-lasting way, modulating the postsynaptic neuron's response to other transmitters ◦ slow-acting transmitters are responsible for changes in a person's psychological state (ex. Sleeps, arousal, motivation [hunger, sexual drive], emotion [fear, anger, joy]) ◦ slow-acting transmitters also trigger permanent changes in neurons that provide the neural foundation for learning ◦ neuropeptide transmitters – relatively large molecules consisting of chains of amino acids ▪ endorphins – a subsset of neuropeptide transmitters that can reduce the experience of pain ◦ biogenic amines – produces states of sleep, arousal, motivation, and emotion ▪ includes dopamine, norepinephrine, and serotonin Mapping the Brain's Behavioral Functions ▪ neurons in the central nervous system are organized into nuclei and tracts • nucleus (“gray matter”)– cluster of cell bodies in the central nervous system (X the same as cell nucleus) • tract (“white matter”)– bundle of axons that course together from one nucleus to another •





◦ referred to collectively as white matter generally neurons who occup the same nucleus and tract have identical or similar functions and groups of nuclei located near one another have closely related functions ▪ three general categories of identifying the function of specific brain areas • observing behavioral deficits that occur when a part of the brain is destroyed or temporarily inactivated • observing the behavioral effects of artificially stimulating specific parts of the brain ◦ transcranial magnetic stimulation (TMS) – a procedure for localizing functions in the human brain ▪ induces an electric current in the neurons immediately below the coil → repetitive pulses cause a temporary loss in the neuron's ability to fire normally OR a single pulse can help map out which muscles are controlled at specific areas within movement-control portion sof the brain through temporary activation ▪ effects are temporary but reversible • recording changes in neural activity that occur in specific parts of the brain when engaged in a particular mental or behavioral task ◦ can be done electrically through the scalp: electrodes placed on a person's scalf → detects and amplifies the signals of continuous electrical “chatter” → results in a record of brain activity (electroencephalogram, EEG) ▪ patterns in EEG can be used as an index of whether a person is highly aroused or relaxed or asleep ▪ event-related potential (ERP) – a brief change in the EEG record immediately following a stimulus ◦ can be done with imaging methods sensitive to blood flow ▪ increased neural activity in any area of the brain is accompanied by increased blood flow to the area ▪ neuroimages – 3-D picctures that depict the relative amount of blood flowing through each part of the brain ▪ positron emission tomography (PET) – first neuroimaging method using radioactive substance ▪ functional magnetic resonance imaging (fMRI) – involves creation of a magnetic field around the head ▪ unlike EEG, PET and fMRT can depict activity anywhere in the brain, not just on the surface near the skull • when done on an animal, more intrusive and permanent lesions (areas of damage) or means of stimulation can be made or done (electrically or chemically) Functional Organization of the Nervous System ▪ nervous system has two distinct but interacting hierarchies • sensor-perceptual hierarchy – involved in data processing ◦ receives sensory data about a person's internal and external environment, and analyzes the data to make decision ◦ flow of information is primarily bottom (sensory receptors) to top (perceptual centers in the brain) • motor-control hierarchy – involved in control of movement ◦ flow of information is primarily top (executive centers that make decisions about actions) to bottom (centers that translate decisions into specific patterns of muscle movement) • bottom parts of the hierarchy are the most evolutionarily primitive and directly tied to the muscles and sensory organs ▪ peripheral nerves • nerves divided into two classes corresponding to the portion of the central nervous system from which they protrude: ◦ cranial nerves – project directly from the brain ◦ spinal nerves – project from the spinal cord, all pairs contain both sensory and motor neurons • nerves exist in pairs (right and left member in each) – 12 cranial pairs and 31 pairs of spinal nerves • sensory neurons provide data needed to govern behavior ◦ sensory input from the specialized sensory organs of the head enters the brain by way of cranial nerves ◦ sensory input that comes from the rest of the body enters the central nervous system by way of the spinal nerves and some of the cranial nerves ▪ somatosensation – the sensations conveyed by the inputs (including touch and pain) • motor neurons are the “final common path” for control of behavior ◦ motor neurons have their cell bodies in the central nervous system and send their axons out by way of cranial or spinal nerves to terminate on muscles or glands •





motor neurons act on two classes of structures: skeletal muscles and visceral muscles&glands ▪ skeletal muscles – musles attached to bones and produce externally observable movements in the body ▪ visceral muscles – muscles not attached to bones and don't move the skeleton when they contract • form the walls of structures like the heart, arteries, intestines, etc. ▪ glands – structures that produce secretions (ex. Salivary glands and sweat glands) ▪ neurons acting on these muscles make up the skeletal portion of the peripheral motor system • skeletal motor neurons initiate activity in the muscles • skeletal muscles are completely inactive in the absence of neural imput ▪ neurons acting on the visceral muscles and glands make up the autonomic portion • autonomic motor neurons typically modulate (modify) rather than initiate activity in the muscles • visceral muscles have built-in nonneural mechanisms for generating activity • most visceral muscles and glands receive two sets of neurons which produce opposite effects and come from two anatomically distinct divisions of the autonomic system (sympathetic and parasympathetic) ◦ sympathetic division – responds to stressful stimulation and helps prepare the body for pssible “fight or flight” ▪ effects include 1)increase heart rate and blood pressure, 2) release of energy molecules(sugars and fats) from storage deposits to permit high energy expenditure, 3) increased blood flow to the skeletal muscles, 4) inhibition of digestive processes ◦ parasympathetic division – serves regenerative, growth-promoting, and energy conserving functions through effects opposity of those listed for the sympathetic division Spinal Cord • connects spinal nerves to the brain and organizes some simple reflexes and rhythmic movements • spinal cord contains ascending tracts (carrying somatosensory info) and descending tracts (carrying motor commands) ◦ severance of the spinal cord will cause paralysis and lack of sensation in the parts of the body innervated by nerves that come from below the place of injury • spinal cord organizes simple reflexes (which don't require the brain) ◦ spinal animals – animals that have the operation of having their spinal cords surgically separated from the brain • spinal cords contain pattern generators for locomotion ◦ pattern generators – networks that activate motor neuroons in the spinal cord in such a way as to produce the rhythmic sequence of muscle movements (ex. Walking, running, flying) ◦ in some animals (not humans) the pattern generators become active when released from the brain's inhibitory control over them Brain • subcortical structures – lower, more primitive parts of the brain ◦ brain stem – organizes instinctive behavior patterns ▪ parts: medulla, pons, and midbrain ▪ functionally and anatomically similar to the spinal cord, except more elaborate ▪ site of entry of most of the cranial nerves (whereas spinal cord is site of entry for the spinal nerves) ▪ contains ascending (sensory) and descending (motor) tracts ▪ contains some neural centers that organize reflexes and certain instinctive behavior patterns • medulla and pons organize reflexes more complex and sustained than spinal reflexes ( including postural reflexes which help with balance, vital reflexes which regulate breathing and heart rate • midbrain contains neural centers that help govern an animal's species-typical movement patterns • midbrain also contains neurons that act on pattern generators in the spinal cord to increase or decrease the speed of locomotion ▪ brain stem animal – animal whose central nervous system is cut completely through just aboce the brainstem ◦ thalamus – relay station for sensory, motor, and arousal paths ▪ located on top of the brain stem, in the middle of the brain ◦







where most sensory tracts terminate in special nuclei → the nuclei send output to specific areas in the cerebral cortex ▪ also has nuclei that relay messages from higher parts of the brain to movement-control centers in the brainstem ▪ plays a role in t he arousal (not the sexual kind) of the brain as a whole cerebellum and basal ganglia – help coordinate skilled movements ▪ anatomically distinct but closed related in function ▪ cerebellum – “little brain”, located at the rear of the brain stem ▪ basal ganglia – set of interconnected structures lying on each side of the thalamus ▪ damage to either can greatly interfere with a person's ability to produce learned, well-coordinated movements • damage to cerebellum associated with loss in ability to behave in ways requiring rapid, welltimed sequences of muscle movements (ex. Pitching a ball, leaping over hurdles) • damage to basal ganglia associated with loss of ability to coordinate slower deliberate movements (ex. picking things up) ▪ both structures specialized to use sensory infor to guide movements – but in different ways • basal ganglia use info in a feedback manner – input pertaining to an ongoing movement → can adjust movements as it progresses • cerebellum uses info in a feed-foward manner – info used to program the appropriate force and timing of a movement before movement is initiated ▪ also active when people are imagining themselves producing movement – when they “visualize” it limbic system and hypothalamus – play essential roles in motivation and emotion ▪ limbic system • acts like a border dividing the evolutionarily older parts of the brain below from the newest part (cerebral cortex) above • consists of distinct structures interconnected with one another in a circuit around the thalamus and basal ganglia ◦ amygdala – involved in regulation of basic drives and emotion ◦ hippocampus – keeps track of spatial location and encodes certain kinds of memories • strongly connected to the nose ▪ hypothalamus • small but important part underneath the thalamus • connected to all the structures of the limbic system • primary task is to help regulate the internal environment of the body by...a) influencing activity of the autonomic nervous system b) controlling the release of certain hormones c) affecting certain drive states such as hunger and thirst cerebral cortex ▪ largest (80% of total volume) and outermost part of the brain, despite being folded inward ▪ divided into left and right hemispheres → each further divided into four lobes, demarcated by rather prominent inwardly folding creases (fissures) • occipital, temporal, periental, and frontal lobes ▪ divided into three categories of functional regions: • primary sensory areas ◦ receives signals from sensory nerves and tract by via relay neclei in the thalamus ◦ includes visual area in the occipital lobe, auditory area in the temporal lobe, and the somatosensory area in the pariental lobe • primary motor area ◦ sends axons down to motor neurons in the central nervous system ◦ part of the chain of command in controlling movements but is not at the top of the chain nor is it involved in all types of movements – receives input from basal ganglia and cerebellum and fine-tunes the signals going to small muscles which operate in a finely graded way ◦ premotor areas – help organize specific patterns of movement ▪ located directly in front of the primary motor area ▪ set up neural programs for producing organized movements ▪ use info sent from anterior (forward) portions of the frontal love that are involved in ▪





overall behavioral planning → chooses what program to set up to execute action program, they send info to the cerebellum, basal ganglia, and motor cortex association areas – all the remaining parts of the cortex ◦ receives input from the sensory areas and lower parts of the brain and are involved in the complex processes of perception, though, and decision-making ◦ prefrontal association areas – create general plans for action ▪ prefrontal cortex – consists of the entire frontal lobe, in front of the premotor areas ▪ involved in both short term and long term planning • areas involved in short term planning use perceptual info sent from posterior association areas to decide on course of action and send info to premotor areas to execute the action primary sensory areas and motor areas are topographically organized in such a way that adjacent neurons receive signals from or send signals to adjacent portions of the sensory or muscular tissue to which they are ultimately connected (principle of topographic organization) ◦ ex. neurons near one another in the visual cortex receive signals from receptor cells near one another in the retina of the eye ◦ amount of cortex devoted to each part of the body corresponds to the degree of sensitivity of that part (sensory map) or the fineness of its movement (motor map) – NOT to size ▪

(can refer to chart for hierarchy of motor control) Effects of Experience on the Brain ▪ experience can change the structure of the brain ▪ new neurons are constantly being generated in the brain ▪ (rats) in enriched environments develop thicker cortexes, larger neurons, more and stronger synaptic interconnections, and generate new neurons faster ▪ restructuring of the cortex happens during skill development – skill learning causes larger portions of the brain to become involved in performing that particular skill • as a person develops skill at a task, more neurons in the brain are recruited into the performance of that skill • ex. in a blind person, areas of the brain usually used by visual people are devoted to other tasks ▪ growth of the hippocampus occurs during spatial learning (which involves memory – i.e. memory for spatial locations) • ex. birds hiding seeds in various locations • ex. cab drivers (in big cities) ▪ strengthening of synapses strengthens the foundation for learning • Hebbian synapse – neurons that fire together wire together ◦ long-term potentiation (LTP) ▪ coordinated firing of a presynaptic and postsynaptic neuron strengthens the synaptic connections of the first onto the second ▪ potentiation (strengthening) of a synapse allows for the presynaptic neurons to trigger a stronger response in postsynaptic neurons than it would have before, given a weak stimulation ▪ LTP involves enlargement of axon terminals and generation of new receptor sites on postsynaptic membranes ▪ LTP is a basis of learning – without it, classical conditioning doesn't work – i.e. neutral stimulus (that doesn't elicit a response) doesn't become a conditioned stimulus, after being paired with a unconditioned stimulus (that does elicit a response) • LTP strengthens synaptic connections in ways that mediate learning ▪ postsynaptic receptors that are involved in initiating LTP come in two forms (strong [which is highly effective in triggering LTP] and weak) Hormones and Drugs in the bloodstrean can affect the nervous system and thus behavior ▪ Hormones – chemical messengers secreted into the bloodstream • chemically similar / identical to neurotransmitters, but travel farther and exert effects on many different target tissues









can influence behavior by affecting bodily growth, metabolism, and brain activity (including those responsible for drives and moods) • effects can be short term, long term or permanent • pituitary gland (controlled by the brain) controls hormone production by other glands Drugs • influence behavior largely by influencing synaptic transmission (by stimulating transmitter release, mimicking transmitter effects, or blocking receptors) • can affect different levels of the behavior-control hierarchy some categories of psychoactive drugs • behavioral stimulants and antidepressants – increase alertness and activity level and elevate mood • tranquilizers and central-nervous-system depressants – counteract anxiety and/or decrease alertness and activity level • opiates – potent pain reducers and can cause feeling of euphoria ◦ produce some of their effects by activating neurons that normally respond to endorphins (class of slowacting transmitters that are part of the body's natural system for relieving pain) • antipyschotic drugs – decreases activity at synapses where dopamine is the transmitters • hallucinogenic drug – induce hallucinations and other sensory distortions ◦ structurally similar to neurotransmitters - believed to act by mimicking or blocking transmitters that they resemble •



Week 6 ◦ sensory systems didn't evolve to provide objective accounts of the world, but rather to provide the specific kinds of information needed in order for the animal to survive ◦ sensation: basic processes by which sensory organs and the nervous system respond to stimuli in the environment and the elementary psychological experiences that result from those processes (i.e. experience of taste, sound, sight) ◦ perception: more complex organizing of sensory information within the brain and the meaningul interpretations extracted from it (i.e. “this is strong coffee”, “my alarm is ringing”, “that's an apple”) ◦ Sensory Processes ▪ process of sensation: physical stimulus → physiological response → sensory experiences • physical stimulus - the matter or energy of the physical world that impinges on sense organs • physiological response – the pattern of chemical and electrical activity that occurs in sense organs, nerves, and the brain as a result of the stimulus • sensory experience – the subjective, psychological sensation or perception experienced by the individual • sensory experience generally tells us something about the physical stimulus but they're very different things ◦ ex. we experience bitterness when we drink coffee, but the bitterness is not a chemical property of it ▪ each sensory system has distinct receptors and neural pathways ▪ sensory receptors: specialized structures that respond to physical stimuli by producing electrical changes that can initiate neural impulses in sensory neurons • can exist in a variety of locations (ends of sensory neurons, in sensory organ, etc) ▪ sensory neurons: specialized neurons that carry info from sensory receptors into the central nervous system ▪ sensory areas: specific areas in the cerebral cortex to which sensory neurons send messages • every sensation experienced consciously is a product of some pattern of activity within a sensory area ◦ you see light because light receptors in the eye are connected to visual areas of your cortex – so theoretically if you could somehow rewire the connections, sending optic nervoes to your auditory brain areas, you could hear light. ◦ You “see stars” due to a bump artificially activating neurons in the visual areas of your brain ▪ sensory receptors generate action potentials through transduction • transduction: a process by which physical stimulation causes receptor cells to respond by producing an electrical change (process differs for each sense, but still has basic similarities) ◦ receptor potential: electrical changes (which can trigger action potentials in sensory neurons) ◦ membrane of the receptor cell become more permeable to certain electrically charged particles when the appropriate type of stimulus energy acts on the receptor cell → charged particles flow through the membrane → electrical charge changes (receptor potential) across the membrane ▪ sensory coding: when sensory systems preserve information about the stimulus quantity and quality in the



patterns of neural activity they produce • transduction occurs such that info preserved in the patterns of action potentials sent to the brain • quantitative variation – intensity or amount of energy (strong, weak, concentrate, dilute) ◦ coded from the fact that stronger stimuli produce larger receptor potentials → faster rates of action potentials in sensory • qualitative variation – precise kind of energy (different wavelengths → different colors, different frequencies → different pitches, different chemicals → different smells or tastes) ◦ qualitatively different stimuli activate different sets of neurons → qualitative variations are coded as different ratios of activity in sensory neurons coming from different sets of receptors ▪ different receptors within any sensory tissue are best tuned to respond to different forms of energy ▪ sensory coding responds to changes more than steady states of stimulation • sensory adaption: the change in sensitivity that occurs when a given set of sensory receptors and neurons is either strongly stimulated or relatively unstimulated for a length of time ◦ when amount of stimulation increases for a period of time, the sensory system tends to become less sensitive and when amount of stimulation decreases, the sensory system adapts by becoming more sensitive than before ◦ usually mediated by the receptor cells themselves ▪ receptor potential and rate of action potentials start high → become reduced over time ◦ sometimes mediated in part by the central nervous system Psychophysics: study of relationships between physical characteristics of stimuli and the psychological sensory experience produced by the stimuli ▪ more mathematical than most other areas of psychology ▪ absolute threshold: the faintest detectable stimulus of any given type • it's a measure of sensitivity that varies person to person • absolute thresholds tend to be higher (meaning sensitivity is lower) for older adults ▪ difference threshold (or just-noticeable difference or jnd): minimal difference in magnitude (intensity) between two stimuli, required for the person to be able to detect a difference ▪ Weber's law – jnd for stimulus magnitude is a constant proportion of the magnitude of the original stimulus • constant proportion varies by sensory task (ex. length judgment and weight judgment) • jnd= kM ◦ M: magnitude or intensity of the stimulus used as the original stimulus ◦ k (Weber fraction): proportionality constant ◦ measured in physical units (despite reflecting a sensory phenomenon) ◦ jnds subjectively equal, but not physically equal • doesn't hold up well when tested at very low (absolute threshold) or very high ranges of stimulus intensity ▪ sensory magnitude is related to stimulus magnitude • Fechner's Logarithmic law ◦ Fechner reasoned jnd could serve as a unit for relating physical and sensory magnitudes as it was a physical unit reflecting a sensory phenomenon ◦ also believed that amount of physical change needed to create a constant sensory change is directly proportional to the magnitude of the stimulus ◦ assumptions: a) every jnd along a sensory dimension is equivalent to every other jnd along that dimension in the amount it adds to the sensory magnitude b)jnd's can be added together • i.e. a sound 100 jnd's above threshold sounds twice as loud as one 50 jnds above, and 1/10th as loud as one 1000 jnd's above threshold ◦ S=c log(M) ▪ S: magnitude of sensory experience ▪ M: magnitude of the physical stimulus ▪ c: proportionality constant ◦ ex. each light bulb of physically equal magnitude thus adds a progressively smaller amount to the perceived brightness → huge intensity range on physical scale, smaller range on psychological scale • Steven's Power Law ◦ method of magnitude estimation – having subjects assign numbers to the magnitudes of their sensation, given a standard stimulus with a starting number ◦ S=cMP ▪ S: reported magnitude of the sensory experience



M: physical magnitude of the stimulus p: power or exponent to which M must be raised • differs from one sensory dimension to another • p<1 → equal physical changes produce smaller sensory changes at the high end of the scale than at the low end - similar to Fetchner's law (ex. brightness) • p>1 → equal physical changes produce greater sensory changes at the high end of the scale than the low end (ex. electric shock) • p=1 → equal physical changes produce the same amount of sensory changes regardless of the strength of the stimulus (ex. Apparent length) ▪ c: constant • value depends on the size of the measurement units used Why a power law? - only a power law preserves constant sensory ratios (among different elements (stimuli) that are being perceived) as the overall intensity waxes or wanes ▪ helps us recognize a pattern as the same patter despite its overall increase or decrease in intensity ▪ ▪



Vision ▪ we're visual creatures who rely on our sight – we forget that what we see and the physical world are not one and the same, our visual perceptions are subjective ▪ Eyes • photoreceptors – specialized light-detecting cells ◦ transduction is the function of the photoreceptors which are located in one layer of the retina ◦ two types (named as such due to their shapes) ▪ cones • ~6 million/retina • permit sharply focused color vision in bright light • concentrated in the fovea ◦ fovea – pinhead-sized area of the retina that is in the most direct line of sight ▪ specialized for high visual acuity (ability to distinguish tiny details) • has three types – each containing a different photochemical ▪ rods • ~120 million/retina • permit vision in dim light • exist everywhere but the fovea, mostly concentrated in a ring ~20º away from the fovea ◦ rhodopsin – a type of photochemical (chemical that reacts to light) found on the outer segment of each rod photoreceptor ▪ when hit by light the rhodopsin molecules undergo a structural change → triggers a series of chemical reactions in the rod's membrane → transduction → electrical response in other cells in the retina → production of action potentials (neural impulses) in neurons that form the optic nerve • retina – multi-layered membrane lining the rear interior of the eyeball ◦ photoreceptors lie in the retina ◦ transduction occurs in the retina • eyeball filled with clear gelatinous substance through which light can easily pass • structures at the front of the eye used for focusing light reflected from objects in such a way as to form images on the retina • cornea – transparent tissue covering the front of the eyeball ◦ convex curvature helps focus light passing through it • iris – opaque, pigmented, doughnut-shaped, lies behind the cornea and provides the color of the eye ◦ doesn't allow light through ◦ muscle fibers in the iris allow it to increase or decrease the diameter of the pupil to control amount of light entering • pupil – the hole in the center of the iris ◦ only way the light can pass through and enter the interior of the eye • lens – located behind the iris ◦ adds to the focusing process ◦ unlike the cornea, the lens is adjustable, becoming more spherical when focusing on objects close to the eye and flatter when focusing on those far away • light rays diverge as they move toward the eye from any given point on a visual object → cornea and lens





bring the light rays back together at a particular point on the retina → forms upside down image on the retina → brain flips image (interprets input lower on the retina as up and vice versa) • optic nerve – runs from the back of the eye to the brain • blind spot – located at the place on the retina where the axons of the neurons forming the optic nerve converge, due to the absence of receptor cells • Rod Vision vs Cone Vision ◦ Cone vision (a.k.a photopic vision or bright-light vision) – specialized for high acuity (ability to see fine detail) and color perception ◦ Rod vision (a.k.a scotopic vision or dim-light vision) – specialized for sensitivity (ability to see in very dim light) ▪ lacks acuity and capacity to distinguish colors ◦ in very dim light, cones aren't activated – you see with only rod vision ▪ you see dim objects best when you don't look directly at them • reason: the fovea which is the part of the retina in the direct line of sight doesn't have any rods ◦ rod's greater sensitivity and cone's greater acuity are in part due to their different neural wiring that connects the receptor cells to the brain ▪ both rods and cones form synapses on short neurons called bipolar cells which in turn form synapses on longer neurons called ganglion cells whose axons leave the eye at the blind spot to form the optic nerve ▪ there is a lot of convergence in connections from rods to bipolar cells to ganglion cells • convergences increase sensitivity by adding together the output of many rods to generate activity in the ganglion cells (like a funnel) • convergence decreases acuity due to the multiple spots of light activating the same ganglion cell (which doesn't send separate messages), resulting in one blurry spot rather than multiple distinct spots ▪ there is little to no convergence when the receptor cells are cones → increases acuity due to each spot of visual stimulation activating a separate pathway to the brain Dark and Light Adaption • rate and degree of adaption are different for rods and cones • dark adaption – gradual increase in sensitivity that occurs when you enter a dark area • light adaption – rapid decrease in sensitivity that occurs when you enter a lighted area • pupils help with dark, light adaption by dilating (widening) in dim light and constricting in bright light ◦ fully dilated pupil allows in ~ 16x as much light • major contribution to dark, light adaption comes from different sensitivities of rods and cones ◦ in bright light, rhodopsin breaks down into two inactive substances (making rod nonfunctional) ▪ only cones are active in bright, even artificial, light → suddenly stepping into darkness → can't see due to rods not being active → takes ~25 min. for rhodopsin to activate ◦ suddenly stepping into bright light → blinded due to highly sensitive rods responding maximally and indiscriminately → takes ~ 5min for rhodopsin to break down ◦ cone photochemicals also break down somewhat in bright light and regenerate in dim light ( but in smaller proportions than in rods) Seeing Color • colors we see depend on the wavelengths of the light reflected from the objects • color varies with the physical stimulus ◦ light is a form of electromagnetic energy – it can be described as both particles and waves ◦ particles are individual packets of light called photons which pulsate in a wavelike way as they travel ◦ light travels at a constant speed ◦ white light (such as that from the sun) contains all visible wavelengths combined ◦ different wavelengths are seen as different colors ▪ shorter end – purple, longer end – red ◦ objects vary in the wavelengths of light they reflect because they have different pigments (chemicals that absorb some wavelengths) on the surface ▪ ex. pigment absorbing short and medium waves appear red • subtractive color mixing – mixing of pigments • additive color mixing – mixing of colored lights ◦ follows two laws – laws of psychology not physics



three-primaries law – three different wavelengths of light (primaries) can be used to match any color that the eye can see if mixed in the right proportions • primaries can be any three wavelengths as long as one each comes from the long-wave, medium-wave, and short-wave ▪ law of complementarity – pairs of wavelengths (complements) can be found that produce the visual sensation of white when added together ◦ standard chromaticity diagram ▪ saturated colors – colors produced by single wavelengths located along the edge of the diagram ▪ unsaturated colors – colors toward the center of the diagram • white is seen as fully unsaturated ◦ wavelengths of the three primaries do NOT become physically blended into one wavelength when mixed together to match the color produced by a fourth wavelength Two Classic Theories of Color Vision ◦ Trichromatic Theory – color vision emerges from the combined activity of three different types of receptors, each most sensitive to a different range of wavelengths ▪ every color is the result of a unique proportion (or ration) of activity among three types of receptors → possible to match any visible color by varying the relative intensities of three primary lights, each of which acts maximally on a different type of receptor ▪ three types of receptors: red cone, green cone, and blue cone ▪ explains the three-primaries law and certain types of blindness ▪ exceptions to the theory • dichromats – people with only two types of cone photochemicals → “red-green color-blind” ◦ obey two-primary law of color mixing ◦ any color they see can be matched by varying the proportion of two wavelengths of light ◦ usually involve absence of photochemical for “green” cones (or “red”), usually in males ◦ “red-green color-blind” means the person has difficulty distinguishing colors ranging from green to red ◦ also happens to most mammals, though birds have four cones ◦ Opponent Process Theory – color perception is mediated by neurons that can be either excited or inhibited depending on the wavelength of light of light, and the complementary wavelengths have opposite effects ▪ derived from and explains law of complementarity ▪ blue-yellow opponent neurons mediates the ability to see blues and yellows • opponent neurons are excited by wavelengths in the blue part of the spectrum and inhibited by those in the yellow part, or vice versa ▪ ability to distinguish bright from dim light (independent of wavelength) is mediated by brightness detectors ▪ explains complementarity of afterimages – by fatiguing neurons in the retina that respond strongly to one color, the opponent-process neurons cause for the complementary color to appear • this adaptive process occurs early in the visual pathway, before the inputs from the two eyes converge ◦ Retina contains three types of cones (trichromatic theory) → cones feed into ganglion cells (neurons of the optic nerve) in a pattern that translates the trichromatic code into opponent-process code ▪

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