University of California, Berkeley

Department of Psychology

Psychology 1

Fall 2007

Midterm Examination 1

Final Scoring Key

In the scoring key that follows, correct answers are marked with an asterisk (*).

The statistical analysis identified five (5) bad items: #s 35, 40, 47, and 49. Theseitems were rescored correct for all responses. Students who got any of these itemswrong, in terms of the preliminary scoring key, should give themselves one (1)additional point for each such item (do not give yourself the additional point if you gota bad item "right").

The average score on the rescored exam was 38.33, standarddeviation = 6.15), or approximately 77% correct. The median scorewas 39. This was excellent performance by the historical standardsof Psych 1, in which my usual mean is somewhere between 65-70%correct.

In what follows, I provide the percentage of the class that got each item correct, aswell as the item-to-total correlation for each item, followed by commentary on whythe right answer is right, and the others wrong.

Choose the best answer to each of the following 50 questions. Questions are drawn from thetext and lectures in roughly equal proportions, with the understanding that there is considerableoverlap between the two sources. Usually, only one question is drawn from each major sectionof each chapter of the required readings; again, sometimes this question also draws on material

discussed in class. Read the entire exam through before answering any questions: sometimesone question will help you answer another one.

Most questions can be correctly answered in one of two ways: (1) by fact-retrieval, meaning thatyou remember the answer from your reading of the text or listening to the lecture; or (2)inference, meaning that you can infer the answer from some general principle discussed in thetext or lecture. If you cannot determine the correct answer by either of these methods, try toeliminate at least one option as clearly wrong: this maximizes the likelihood that you will get thecorrect answer by chance. Also, go with your intuitions: if you have actually done the assignedreadings and attended the lectures, your "informed guesses" will likely be right more often thanthey are wrong.

Be sure you are using a red Scantron sheet.

Fill in the appropriate circles with a #2 pencil only.

Be sure you put your name on the front of the red Scantron sheet.

Be sure you put your Student ID# on both sides of the red Scantron sheet.

Indicate Exam 001 (use all three digits) on the reverse side of the red Scantron sheet.

Retain this exam, along with a record of your answers.

1. Let!s say you want to assess the effect of subliminal suggestions on ratings ofattractiveness. You ask 20 students to listen to subliminal tapes, then have them rate theattractiveness of 20 peers. You discover that all the peers were rated as highly attractive,with a mean of 8 out of a possible 10. Why is the above experimental design inadequate?

a. It lacks demand characteristics.

b. It lacks an independent variable.

c. It lacks a dependent variable.

d. It lacks a control group.*

91% correct, item-to-total rpb = .18. 8/10 compared to what? Without a control or

comparison group, which doesn't receive the subliminal suggestion, we have no ideawhether the suggestion has an effect. With a proper control group, the presence orabsence of the subliminal suggestion would be the independent variable, while theattractiveness rating is the dependent variable. All experiments have demandcharacteristics, which are subtle cues contained in the experimental situation thatcommunicate the purpose of the experiment to the subject.

2. Which of the following can be a significant problem for correlational studies?

a. It is nearly impossible to find an effect in most studies.

b. It can be hard to tell which factor is causing the other.*

c. Demand characteristics can be a significant problem.

d. Placebo effects can be a significant problem.

90%, rpb = .27. People commonly confuse correlation with causation. Two variables may be

correlated because they are in a cause-and-effect relation. Or they may be correlatedbecause they are both the effects of some third cause.

3. Which of the following is most relevant to a study!s external validity?

a. the degree to which the study!s participants reflect the greater population*

b. the degree to which the study is measuring what it claims to be measuring

c. the fact that the study is conducted outdoors

d. the degree to which the study!s participants are different from the greater population

95%, .31. External validity has to do with the degree to which experimental results can begeneralized to the population as a whole. On some dimensions, college students -- whoserve as subjects in the vast majority of psychological experiments -- may be quite differentfrom most other people, which threatens the external validity of the research in question. Ofcourse, on other dimensions, we are all pretty much alike, so relying on college students isnot so much of a problem.

4. A psychological explanation of behavior is in terms of:

a. brain activity.

b. the individual!s state of mind*

c. objectively recorded data.

d. sociocultural factors that impinge on the individual.

76%, .30. Psychology is rooted in the doctrine of mentalism, which states that behavior is to

be explained in terms of the individual's particular cognitive, emotional, and motivationalstates. The biological level of explanation depends on such things as genes, evolution, andbrain processes. The sociocultural level depends on such things as organizationalstructure, dominance hierarchies, tradition, and the like.

5. The key idea in Darwin !s theory of natural selection is as follows:

a. Evolution favors the better or more advanced organism.

b. Evolution favors the organism that is better suited to its current environment.

c. Variations in a species sometimes lead to reproductive advantage.

d. Both b and c are correct.*

78%, .21. For Darwin, some inter-individual variation occurs naturally in every species,because of the way that inheritance (meaning genetics). Occasionally, some variantenhances the organism's fitness for its environment, and this genetic advantage is passedto the offspring of the favored individual. But it's not that the favored individual is moreadvanced. Cockroaches fit better in some environments than people do, but that doesn'tmean that cockroaches are more advanced creatures than humans.

6. What does homeostasis produce?

a. a predictable increase in the number of action potentials

b. a predictable increase in one!s basal metabolic rate

c. a stable internal equilibrium*

d. a cue for positive feedback

97%, .34. Homeostasis is the process by which organisms maintain their internalenvironments as stable levels: we eat when blood sugars drop below a certain level, andstop eating when optimal levels of blood sugar have been restored.

7. The autonomic nervous system has two branches: the sympathetic and theparasympathetic. What does each do?

a. The sympathetic revs up bodily activities, the parasympathetic restores the body!sactivities to normal.*

b. The sympathetic sends messages to the glands, the parasympathetic to the smooth

muscles.

c. The sympathetic provides positive feedback, the parasympathetic negative feedback.

d. The sympathetic restores homeostasis, the parasympathetic revs the body up.

96%, .24. Think of it this way: sympathy is a feeling, and the sympathetic nervous systemmediates, among other things, emotional arousal. Paramedics help restore health, and theparasympathetic nervous system acts to restored, or slow the depletion of, bodily resourcesdepleted by sympathetic activity. In this way, the sympathetic and parasympatheticbranches are antagonistic to each other, going in opposite directions.

8. What can be said about external cues, such as the sight of food?

a. They act independently of internal cues such as feelings of satiety.

b. They are more likely to lead to eating in the context of hunger than satiety.*

c. They are more likely to lead to eating in the context of satiety than hunger.

d. They have no effect on the hypothalamus.

73%, .37. External cues like the presence of food tend to elicit eating behavior under anycircumstances, which is why people eat when food is available, even though they're nothungry. But the effect of external cues is much greater when people are actually hungry. This is what we would call an interaction between external cues (presence of food) andinternal cues (hunger pangs), about which more later in the course.

9. One form of violence that organisms engage in is called predation. Such predatory attacksseem to be an outgrowth of

a. dominance hierarchies.

b. hormonal imbalance.

c. intense arousal.

d. the hunger motive.*

76%, .40. Predation is behavior in which an organism of one species attacks an organism ofanother species, and is closely related to hunger. Aggression is different, because in thiscase the attack is by one species member against a conspecific organism.

10. How do humans and animals differ in their sexual response?

a. Human females are under strict hormonal control, but female animals are not.

b. Female animals are under strict hormonal control, but human females are not.*

c. Human males are reliant on testosterone for sexual arousal, while male animals are relianton progesterone for sexual arousal.

d. Human males are reliant on progesterone for sexual arousal, while male animals arereliant on testosterone for sexual arousal.

81%, .48. Mating in nonhuman animals is strictly for purposes of reproduction, and thus istightly controlled by hormones (particularly female hormones). It's instinctual. But humanmating serves both reproductive and "recreational" purposes. Which is why humans, butnot nonhuman animals, will mate at times, and in ways, that can't lead to procreation.

11. Many processes in the brain functioned essentially mechanically, according to Descartes,but what truly governed our behavior, what made humans different from animals, whatmade reason and choice possible, was

a. language.

b. the ego.

c. intelligence.

d. the soul.*

64%, .38. Psyche is Greek for "soul", a concept that has been secularized so that psychologymeans the science of the mind, not the science of the soul. For Descartes, soul and mindwent together, and only humans had either one. Language may distinguish humans fromother animals, but that wasn't Descartes' view. And the discussion of learning shows thateven nonhuman animals can be intelligent.

12. The various new neuroimaging techniques are powerful, but at the same time

a. they do not, on their own, tell us whether a particular brain activity is a cause or aconsequence of a given psychological process.*

b. they tend to yield extremely inconsistent data.

c. none of them can show changes in the brain!s minute-by-minute functioning.

d. they can cause brain damage in certain individuals.

90%, .34. Neuroimaging techniques allow us to see the brain at work, but in order tounderstand the meaning of the brain activity we have to have a correct understanding of theexperimental task at the psychological level of analysis. Neuroscience thus depends onpsychology.

13. __________ are bundles of neurons that conduct excitation toward the brain or spinalcord.

a. Receptors

b. Effectors

c. Efferent nerves

d. Afferent nerves*

85%, .42. Think of it this way: affects are feelings, and afferent neurons, bundled into afferentnerves, carry sensory impulses from the sensory receptors to the central nervous systemso that they can be "felt". Effects are actions, so to speak, and efferent neurons, bundledinto efferent nerves, carry messages to stimulate the activity of effectors such as themuscles and internal organs.

14. The large brain structure that controls key life functions such as breathing, level ofattentiveness, and the timing of sleep and dreaming is called the

a. hindbrain.*

b. midbrain.

c. forebrain.

d. cortex.

59%, .35. The hindbrain (like the pons and the medulla) mediates vegetative functions, whichis why people can live, even if they're comatose, following damage to midbrain structureslike the reticular formation. The forebrain consists of the cerebral cortex, as well as

subcortical structures like the hippocampus and amygdala.

15. Which of the following statements best describes the current scientific view regarding thefunctioning of our left and right hemispheres?

a. The hemispheres constantly compete for dominance over our daily activities.

b. The left hemisphere is our major hemisphere, while the right hemisphere plays only aminor role in daily activities.

c. The left hemisphere tends to be analytic, while the right hemisphere tends to be artistic.

d. Together, the left and right hemispheres contribute their specialized abilities to every task.*

71%, .24. The two hemispheres aren't quite identical, and they're not precisely redundant:there's hemispheric specialization, just like there's functional specialization within eachhemisphere. For example, for most people language functions are localized in the lefthemisphere, while the right hemisphere is particularly good at pattern perception. It's not amatter of analytic versus artistic: the right hemisphere is good at analyzing patterns, whilepoets and composers use their left hemispheres quiet a bit. But, just as with functionalspecialization, most mental and behavioral tasks require the integrated and coordinatedactivity of numerous brain "centers". The hemispheres are no exception. For example, inorder to play the piano you have to be able to coordinate your left hemisphere (whichcontrols your right hand and foot) with your right hemisphere (which controls your left handand foot). That what the corpus callosum is for: to permit to two hemispheres tocommunicate with each other.

16. The brain seems to consist of a large number of separate and specialized modules. There is, in other words, a localization of brain function. At the same time, research alsohas shown that

a. which module performs which task varies from person to person.

b. there are no links from one module to another.

c. multiple brain areas are activated for any task we do.*

d. All of the above are correct answers.

92%, .41. What goes for the two hemispheres goes for the modules within the hemispheres.

17. In which lobe would you expect neurons to be most reliably activated by the stimulation ofa nerve receiving sensory information from the skin of the knee?

a. frontal

b. parietal*

c. occipital

d. temporal

79%, .31. The somatosensory area is located in the parietal lobe, adjacent to the centralfissure. The primary motor cortex is located in the frontal lobe, adjacent to the centralfissure. The primary auditory area is located in the temporal lobe, adjacent to the lateralfissure. And the primary visual area is located in the pole of the occipital lobe.

18. Bob is hit on the head and !sees stars. ! The region of the brain that was most likelyaffected is the __________.

a. cerebellum

b. frontal cortex

c. occipital lobe*

d. limbic system

85%, .25. And the primary visual area is located in the pole of the occipital lobe. Thesomatosensory area is located in the parietal lobe, adjacent to the central fissure. Theprimary motor cortex is located in the frontal lobe, adjacent to the central fissure. Theprimary auditory area is located in the temporal lobe, adjacent to the lateral fissure. Thecerebellum coordinates sensory and motor functions. The limbic system is involved inemotional reactions.

19. From what you know about the position of the various brain areas, which of the followingseems most probable?

a. Damage to Wernicke!s area is more likely to be accompanied by paralysis than is

damage to Broca!s area.

b. Damage to Wernicke!s area is more likely to be accompanied by deafness in the left earthan in the right ear.

c. Damage to Broca!s area is more likely to be accompanied by paralysis of the left armthan by paralysis of the right arm.

d. Damage to Broca!s area is more likely to be accompanied by paralysis than is damage to

Wernicke!s area.*

64%, .41. Broca's area is located in the frontal lobe, adjacent to the primary motor cortex. Therefore, extensive damage could knock out both speech functions, leading to expressiveaphasia, and voluntary motor functions, leading to paralysis of some motor functions(including, if the damage is really extensive, hemiplegia). Some of you went for Option A,but Wernicke's area is in not in the frontal lobe. Some of you went for Option B, butWernicke's area is in the left hemisphere, and damage to the adjacent auditory cortexwould produce deafness in the right (contralateral) ear.

20. In the lock-and-key model of synaptic transmission, the !key! gets to the !lock! by

a. removal of synaptic vesicles.

b. rapid conduction down to the axon.

c. weak attractive forces of the lock.

d. diffusion across the synaptic gap.*

90%, .42. Neurotransmitters secreted by the synaptic vesicles of the pre-synaptic neuron flowinto the synaptic cleft, where they are picked up by the dendrites of the postsynapticneuron; those that are not are cleaned away or returned to the presynaptic neuron throughsynaptic reuptake. But uptake by the postsynaptic neuron only happens if theneurotransmitter molecule is of the right shape to fit into the receptors of the postsynapticneuron. Thus, neurotransmitters aren't interchangeable: there are specificneurotransmitters whose moleculer "keys" fit into postsynaptic "locks". Some psychoactivedrugs modulate neural activity by affecting the lock-and-key mechanism.

21. In young children, recovery of speech and other brain functions following injury is more

likely than it is for adults. Thus, we say that a child!s brain has __________ than an

adult!s.

a. less transduction

b. more transduction

c. less plasticity

d. more plasticity*

96%, .32. Transduction has to do with the conversion of a proximal stimulus (see below) intoa neural impulse. Plasticity has to do with the brain's ability to alter its structure andfunction in response to changing circumstances. As a rule, children's brains are moreplastic than adults', so that recovery of function due to damage to some portion of the brainis more likely to occur in children than in adults. It may be that some brain modules arespecialized for various functions, but if these modules are damaged the immature brainmay have enough plasticity -- enough flexibility -- to permit some other module, not initiallydedicated to that function, to take over. But even mature brains show some degree ofplasticity -- otherwise, we'd never learn anything.

22. More than anything else, when the early Empiricist philosophers sought to offer anaccount of learning, they focused on:

a. associations.*

b. the creation of belief systems.

c. how learning leads to the creation of new skills.

d. the creation of elaborate belief systems.

65%, .27. Empiricism is the philosophical contrast to nativism: Nativists believed thatknowledge was innate, while empiricists believed that knowledge was acquired throughexperience -- that is, through the creation of associations through learning. A lot of youwent for C, which doesn't have anything to do with the debate between Nativists andEmpiricists.

23. An obvious benefit of habituation is this:

a. It narrows the range of stimuli that elicit alarm.

b. It guarantees that we will respond to novel inputs.

c. It leads to enduring brain changes in the hippocampus.

d. Both a and b*

55%, .16. In habituation, response to a stimulus declines with repeated presentation of thatstimulus. By virtue of habituation, organisms don't respond (with alarm or arousal) to everystimulus that occurs in their environment. Rather, response is reserved for novel stimuli.

some students may have been misled by the word "guarantees" in Option b, on the groundthat, in taking multiple-choice tests, you should avoid extreme statements. "Guarantees"might not have been the best choice of word here, but here's where the statistical analysiscuts objectively cuts through subjective impressions. The item proved to be "good" instatistical terms, and if I rescored the item based solely on subjective impressions, I risklapsing into solipsism -- there's no point in doing the statistical analysis if you're not going touse the information to evaluate items.

24. Unconditioned responses by definition occur

a. independent of any learning.*

b. only in lower organisms.

c. only in conditions of deprivation.

d. only in response to secondary reinforcers.

95%, .35. URs are reflexive responses to stimulation, and reflexes are, by definition, innatestimulus-response associations, hard-wired into the nervous system. Reflexes are alsoautomatic, in that they occur regardless of the circumstances in which they are elicited.

25. The speed of relearning confirms which of the following facts?

a. You can!t teach an old dog new tricks.

b. We learn better when under pressure.

c. Extinction does not erase initial learning.*

d. The effects of initial learning always outstrip subsequent learning.

93%, .41. Savings in relearning after extinction, like spontaneous recovery, indicates that theextinguished CR is not lost, but rather inhibited.

26. When does stimulus generalization occur?

a. when an organism responds to a range of stimuli that are similar to the original CS*

b. when an organism produces several slightly different responses to the same CS

c. when an organism responds only to a particular CS

d. when an organism responds to second-order conditioning

93%, .40. Stimulus generalization occurs when an organism responds to stimuli other thanthe one to which it has been conditioned. Generalization follows a gradient, meaning thatresponse is greatest to new stimuli that most closely resemble the original conditionedstimulus.

27. Which of the following statements is false?

a. Initially, discrimination training results in generalization.

b. In discrimination learning, the CS+ takes on significance opposite of the CS!.

c. The CS! takes on the role of the inhibitor.

d. While the CS+ predicts the occurrence of the US , the CS! conveys little or noinformation.*

58%, .37. In the early phases of discrimination training the organism's responses areindiscriminate -- that is, it generalizes the CR to the CS- as well as the CS+. However, iteventually learns that the CS+ predicts the US, while the CS- predicts the absence of theUS. At this point, the CS- inhibits the CR, while the CS+ elicits the CR. So, both the CS-and the CS+ convey information to the organism: the CS+ about the presence of the US,the CS- about its absence. Some of you went for Option A, but the initial response to a CS-is, in fact, a generalized CR.

28. What will happen in a classical conditioning experiment if the likelihood of the USfollowing the CS is 30 percent and the likelihood of the US being presented alone is also 30percent?

a. There will be no conditioning, no matter how contiguous the CS and US.*

b. There will be strong conditioning if the US arrives about half a second after the CS.

c. There will be no obvious effect at first, but after a rest period the CR will appear when theCS is presented.

d. The animal will show surprise reactions when the CS is presented.

51%, .26. Conditioning occurs when the probability of the US occurring in the presence of theCS is greater than the probability of the US occurring in its absence. In this case, the twoprobabilities are equal. Therefore, no conditioning will occur. A lot of you went for Option

C, but that has to do with spontaneous recovery.

29. A phenomenon called the !blocking effect! demonstrates the key role played by__________ in conditioning.

a. intelligence

b. genetics

c. desire

d. surprise*

52%, .33. In Kamin's blocking experiment, the animal is conditioned to CS1, and then to acompound of CS1 and CS2. Because the US and the CS-US relationship, haven'tchanged, the CS2 is redundant with CS1. Because CS2 provides no new information tothe organism, no conditioning will occur to CS2. Conditioning occurs only when the USsurprises the organism. In the blocking experiment, no surprise occurs because theorganism already has a good predictor of the US -- namely, CS1. Some of you went forOption A, presumably on the ground that Kamin's experiment shows that learning isintelligent, and not just a matter of conditioning, but choosing that option didn't correlatewith overall test performance: in fact, the correlation was negative (-.11).

30. According to Thorndike!s !law of effect,!

a. punishment has little effect on behavior.

b. rewarded responses are strengthened.*

c. learning usually results from sudden insights or sudden solutions to problems, notgradually.

d. punished responses are paradoxically strengthened.

96%, .26. Thorndike's Law of Effect says that conditioned responses are graduallystrengthened by reward and gradually weakened by nonreward, but it says nothing aboutpunishment. And it says nothing about insight.

31. During training, in classical conditioning, the US is presented __________, while in

operant conditioning the reward is presented __________.

a. during every test trial; only on a variable interval schedule

b. immediately after the response; immediately before a response

c. regardless of behavior; contingent on behavior*

d. contingent on behavior; regardless of behavior

88%, .44. In classical conditioning, reinforcement (the US) is presented contingent only on theCS, regardless of what the organism does. For Pavlov, bell is followed by food no matterwhat the dog does. In Kamin's blocking experiment, noise is followed by shock regardlessof what the rat does. By contrast, in instrumental conditioning reinforcement (the reward) iscontingent on the organism making the conditioned response. For Thorndike, the cat getsout of the cage only if it presses the paddle. And for Skinner, the pigeon gets a food pelletonly if it pecks the key.

32. Gamblers often persist at gambling even when they very rarely receive a payoff. How canone explain this persistence?

a. There is a gradual increase in performance with successive approximations.

b. There is a strong resistance to extinction when performance has been maintained with avariable schedule of reinforcement.*

c. Typically, the gambler will pause for a brief rest after each case of reinforcement, therebyincreasing stamina.

d. The gambler experiences learned helplessness and is unable to stop.

86%, .35. This is about schedules of reinforcement in instrumental (operant) conditioning. You can think of pulling the lever of a slot machine as a conditioned response. In slots,reward is presented on a variable-ratio schedule, with a very low ratio setting, meaning thatthe gambler has to make lots of conditioned responses (lever pulls) before it gets anyreward. Under these circumstances, the organism -- the gambler -- will emit a largenumber of conditioned responses -- lever pulls - -even though individual responses arerarely rewarded. The gambler is essentially on an extinction schedule, because lever pullsrarely deliver reward. But still, lever-pulling persists -- indicates strong resistance toextinction. Successive approximations (Option A) are characteristic of shaping. Pauses inresponding (Option C) are characteristic of fixed-interval schedules of reinforcement,because reinforcement will not be delivered again for a period of time, regardless of whatthe organism does. In learned helplessness (Option D), the organism has learned not tomake the CR: the problem is starting to respond, not stopping.

33. What does latent learning show?

a. Learning can occur without behavioral change.*

b. Learning can occur suddenly, in a single trial.

c. Learning will not occur if blocking is present.

d. Learning requires a certain amount of response control.

67%, .40. This is about Tolman's experiment (Tolman, after whom Berkeley's Tolman Hallwas named; Gleitman, your textbook author, was Tolman's PhD student), in which onegroup of rats was simply allowed to explore a maze, without receiving any reward. Nevertheless, when reward was introduced, they quickly found their way to the goal box --showing that they had learned the "map" of the maze during the exploration trials. So,learning can occur in the absence of reinforcement. And learning can occur in the absenceof behavioral change -- behavior changes when there is an incentive, such as theintroduction of food into the goal box, for the animal to use (display) what it has learned. Behavior changed suddenly when the incentives were changed. But the learning hadoccurred gradually, on the earlier exploration trials.

34. Rats A and B receive shocks in a Skinner box. Rat A can terminate the shock by pressinga bar. For rat B, there is no response that leads to shock termination. The experimenterthen tries to teach both rats another similar shock-avoidance task. What result would oneexpect?

a. Rat A will learn the avoidance task more quickly than rat B.*

b. Rat B will learn the avoidance task more quickly than rat A.

c. The rats will learn the avoidance task at equal rates.

d. Neither rat A nor rat B will be able to learn the avoidance task.

93%, .24. This is about learned helplessness. Rat A has learned that there is something itcan do to escape shock. Rat B has learned that shock occurs regardless of what it does. Therefore, A will learn the new shock-avoidance task more readily than B. B already"knows" that shock is uncontrollable, and that it is helpless in such situations.

35. Which of the following is an aspect of neural plasticity that allows learning to occur?

a. the formation of synapses

b. changes in neuronal sensitivity to stimulation*

c. changes in synaptic function

d. all of the above

15%, .06. A bad item. The neural basis of learning appears to be long-term potentiation(LTP), by which we mean a change in the sensitivity of post-synaptic neurons to stimulationby presynaptic neurons. Think of the reflex arc: with learning, the efferent neuron(mediating response) is more likely to be excited by stimulation from the afferent neuron(mediating the stimulus), passed through the interneuron (mediating the associationbetween them). New synapses aren't formed during learning, but by virtue of LTP,transmission across some synapses is facilitated. Most of you went for Option D, but theplasticity that allows learning doesn't extend to the formation of synapses, which rules outOption A, and thus Option D as well. What changes in learning is the ease of synaptictransmission, not the structure of the synapse as well. Now, that might mean that Option Cis correct, which might also push people toward Option D. And after all, Option C refers tochanges in synaptic function, which is one way of thinking abut changes in neuronalsensitivity to stimulation.

36. A man is looking at a tree. What is the proximal stimulus?

a. the tree

b. the light waves reflected by the tree

c. the image cast by the tree on the man!s retina*

d. the pattern of nerve impulses triggered by the retinal image and conducted by the opticnerve to the brain

37%, .25. A hard item, but a fair one, especially since I think I've asked a question like this onevery exam covering sensation and perception. The distal stimulus refers to an object inthe environment -- in this case, a tree. The tree reflects light, which may be why so manywent for Option B. But the proximal stimulus refers to the light waves that fall on the man's

retina, creating an image of the distal stimulus. By virtue of transduction by the rods andcones in the retina, the proximal stimulus is converted into a pattern of neural impulsescarried over the optic nerve to the visual cortex in the occipital lobe of the brain.

37. The smaller the Weber fraction,

a. the less sensitive the sense modality.

b. the higher the response criterion.

c. the more sensitive the sense modality.*

d. the shorter the duration of response to any sensory impression.

67%, .38. In psychophysics, the Weber fraction is the ratio that must be added to a stimulusto produce a just-noticeable difference in the intensity of that stimulus. It is, effectively, aconstant across wide ranges of stimulation. So, if it takes 1 unit to produce a change in astimulus of 100 units (Weber fraction = 1/100), it will take 2 units to produce a change in astimulus of 200 units (Weber fraction = 2/200 = 1/100). Low ratios mean that very littleintensity must be added to produce a noticeable change -- which means, in turn, that thesensory modality is very sensitive to change, responding even to very small amounts ofchange.

38. What is a major advantage of signal-detection methods over traditional ways ofmeasuring thresholds?

a. Signal-detection methods allow the investigator to distinguish between sensitivity effectsand tendencies to respond too conservatively or too liberally.*

b. Signal-detection methods allow the investigator to separate hits and misses from correctnegatives and false alarms.

c. Signal-detection methods allow the investigator to introduce occasional !catch! trials toeliminate response biases.

d. Signal-detection methods allow the investigator to multiply the effects of sensitivity by themagnitude of the response bias.

39%, .39. Traditional psychophysics views the observer as passive: detection is simply amatter of their being enough intensity in the proximal stimulus. But signal detectionassumes that the observer is active -- has expectations about whether the stimulus will bepresented, and motives to detect the stimulus or not. By varying the number of catch trials,and by varying the consequences for being right or making a mistake, signal detectionmethods attempt to take account of these cognitive and motivational factors. A lot of youwent for Option B, but the whole point of separating hits and misses is to take account ofexpectations and motives.

39. According to the doctrine of specific nerve energies, why do we experience differences in

the sensory quality of the taste of iced tea, the sound of birds singing, and the sight of afireworks display?

a. because of our past experiences with these particular stimuli

b. because different sensations excite different nervous structures*

c. because there are physiological differences in the conduction speed of the neurons that areassociated with different sense organs

d. all of the above

52%, .47. The doctrine of specific nerve energies says that each modality is defined by aparticular neural pathway, not by a particular proximal stimulus. Thus, what makes visiondifferent from audition is not the difference between electromagnetic radiation andmechanical vibration; it's the difference between the rods and cones and the basilarmembrane; between the optic nerve and the auditory nerve; and, especially, between theauditory and visual projection areas. A lot of you went for Option D, but Option A is clearlywrong, and the problem with Option C is that it's not conduction speed, but conductionpathways that define the specific nerve energies.

40. Which theory explains why we hear tones below 500 hertz?

a. the theory of cochlear vibration

b. pitch theory

c. frequency theory*

d. place theory

46%, .09. A bad item, even though I often ask a question like this. Pitch is related to thefrequency with which the proximal stimulus vibrates. Perhaps the easiest way to producethe sensation of auditory pitch would be to translate the frequency with which the proximalstimulus vibrates into the frequency of vibration of the basilar membrane, and thereafter intothe frequency of the neural impulse carried through the auditory nerve. Unfortunately forthis proposal, we can hear frequencies up to 20,000 cps, and neurons can't fire that fast. According to the duplex theory of pitch, low pitches (associated with low frequencies, up toabout 5,000 cps) are represented by the frequency with which the basilar membranevibrates; but high pitches (associated with high frequencies, about 1,000 cps and above)are represented by the place at which the basilar membrane vibrates maximally. These twoprinciples account for auditory pitch: frequency for low pitches, place for high pitches

41. What does the duplex theory of vision propose?

a. We have two eyes, each with a slightly different view of the world.

b. There are two separate receptor systems, one for color vision and one for monochromaticvision.*

c. Ganglion cells are activated when the lights go on and bipolar cells are activated when thelights go off.

d. Our visual system is made up of two types of stimuli, the proximal stimulus and the distalstimulus.

45%, .38. Two-process theories abound in psychology, and here's another one. The retinaholds two kinds of cells sensitive to light: rods, which are very sensitive even to lowintensities of light, but not to color -- thus producing monochromatic vision of dark, light, andgray; and the cones, which are sensitive to color -- red and green, yellow and blue, andeverything else -- but not to low intensities of light. Bipolar cells receive neural impulsesfrom the rods and cones, and then pass them on to ganglion cells. But what's reallyimportant at the level of the introductory course is the different characteristics of rod andcone vision. A lot of you went for Option A, which has to do with binocular convergence, notthe fact that there are two separate receptor systems, rods for monochromatic vision andcones for color vision.

42. What negative afterimage would you see if you were presented with a blue-coloredsquare?

a. a red-colored square

b. a black-colored square

c. a yellow-colored square*

d. a green-colored square

79%, .45. This is the kind of evidence that led to formulation of the opponent-process theoryof color vision, which holds that color vision is a product of two opponent-process systems,one for red and green, the other for yellow and blue (there's also a third opponent-processsystem for light and dark). These opponent processes are organized in an antagonisticrelation to each other (antagonism is another common principle in psychology, as with thesympathetic and parasympathetic nervous systems), such that stimulation of one elementsuppresses or inhibits the other. Thus, stimulation of the blue element in the yellow-bluepair activates the blue process, but inhibits the opponent yellow process. When the bluestimulus is terminated, the blue process goes off and the yellow process springs back --thus producing the negative afterimage of yellow.

43. A person with only one eye could perceive depth by using which cue(s)?

a. linear perspective

b. texture gradients

c. relative size

d. all of the above*

89%, .33. Cues to depth come in four basic categories: ocular, depending on feedback fromthe eye itself; and optical or pictorial, such as you would find in a pictorial representation ofthree dimensions on a two-dimensional canvas. Moreover, binocular cues depend oninformation from both eyes, while monocular cues work even with information from only oneeye. Most optical or pictorial cues are monocular in nature; the only exception is retinaldisparity, which obviously involves two eyes, two retinas, and the disparity between theirimages.

44. What would happen if you suddenly experienced an involuntary twitch of one of your eyemuscles?

a. The world would seem to move.*

b. The world would remain stationary.

c. There would be a momentary !blank! time in your perceptual experience.

d. You would experience motion parallax and optic flow.

48%, .41. A hard item, but fair. One of the cues to motion is the movement of an imageacross the retina. But when you move your eye voluntarily, you don't perceive the object asmoving: the world appears stationary even though the images move on the retina. This isbecause the visual system automatically compensates or the voluntary movement of theeye. But when your eye twitches, the eye moves involuntarily, and the information thatwould ordinarily come from the voluntary movement isn't available. So, all the visual system"knows" is that the image is moving, and so the object is perceived as moving.

45. Which general law(s) tie(s) the Gestalt grouping factors together?

a. the laws of feature detection

b. the law of perceptual constancy

c. the law of serial processing

d. the laws of perceptual organization*

60%, .34. Gestalt is German for "form", and all the Gestalt principles are about how theperceiver organizes the entire pattern of stimulation into the best form possible. So, wetend to perceive similar figures as belonging together, and closer figures as belongingtogether, and we group line segments together so as to produce smooth contours. Theseelements of form are not necessarily in the stimulus -- they are products of theorganizational activity of the perceptual system.

46. What do reversible figures demonstrate?

a. Perceptual parsing is not inherent in the stimulus.*

b. Perceptual parsing is inherent in the stimulus.

c. Figure-ground relationships are inherent in the stimulus.

d. Figure-ground relationships are stable.

56%, .38. Parsing is something the subject does (we'll encounter this term again in Gleitman'schapter on language). Far from being something that's inherent in the stimulus, it'ssomething the perceiver does to make sense of stimulus information. In reversible figures,we can see the same stimulus as two quite different objects, depending on "how we look atit" - -for example, the vase-face figure or the "wife/mother-in-law". The importance of thereversible figures is that they show that not all the information needed for perception isgiven by the stimulus; there is also a cognitive contribution from the knowledge andexpectations of the perceiver.

47. Which of the following best describes the phenomenon of perceptual constancy?

a. Our perception of an object changes when the proximal stimuli changes.

b. Our perception of an object remains the same in spite of changes in the proximal stimuli.*

c. Our perception of an object changes when the distal stimuli changes.

d. Our perception of an object remains the same in spite of changes in the distal stimuli.

8%, -.11, a really bad item, because the preliminary scoring key had the right answer as A,which is clearly wrong, instead of B, which is clearly right. This is just a typo on my part,when creating the scoring key. Mea maxima culpa. We could have simply rekeyed thisitem, but in my absence my instructions to the GSIs were simply to rescore bad itemscorrect for all responses. Because students who chose the right answer, B, got credit, noharm has been done. Anyway, the perceptual constancies make the same point as thereversible figures, but in the opposite way. Here, perception of an object remains constantdespite quite substantial changes in the pattern of proximal stimulation. It's as if the visual

system compensates for certain stimulus changes, so that the percept remains stable. Ifthe percept remains stable despite changes in the stimulus, then all the information forperception isn't provided by the stimulus; some of the information must be provided by theperceiver.

48. Being able to identify an ambiguous stimulus illustrates which major point aboutperception?

a. Perceptual systems depend mainly on top-down processing.

b. Perceptual systems have great difficulty adapting to ambiguous stimuli.

c. Perception is an active process.*

d. We make a large number of perceptual errors on a regular basis.

70%, .29. Unpacking the information contained in a stimulus is a matter of bottom-upprocessing. Adding information to a stimulus is a matter of top-down processing. So it'sthe same point again -- are you getting the idea that this is the most important point of thelectures (and readings) on sensation and perception. Ambiguous stimuli are ambiguousprecisely because they don't contain enough information for the perceiver to disambiguatethem. Rather, the perceiver has to rely on his or her knowledge, expectations, and beliefsto, in Bruner's phrase, "go beyond the information given" by the stimulus.

49. Which area(s) of the cortex is (are) directly involved in processing visual information?

a. occipital

b. temporal

c. parietal

d. All of the above areas of the cortex are involved.*

19%, .08, a bad item, maybe because it was a little tricky, but it was only a little tricky, and thepoint at stake is important. The occipital lobe contains the primary visual cortex, which isprobably what 77%of you had in mind when you chose Option A -- though, interestingly, theitem-to-total correlation for A was a measly 0.03. But there's more to visual perception thanthat. Even though there are modules in the occipital lobe that process various aspects ofvision, the limits on localization of function apply to vision, just as they do to language. Thatis to say, visual processing, like language processing and everything else, depends on theintegrated and coordinated activity of a number of different brain modules. So, for example,there are areas in the temporal cortex and the parietal cortex that are also involved in vision-- a "what" system in temporal cortex that identifies the object, and a "where" system inparietal cortex that locates objects in space. As another example, prosopagnosia, aninability to recognize faces and other objects at a subordinate level of categorization (more

on levels of categorization later), results from brain damage at the junction of the temporaland parietal lobes.

50. Which aspect of perceptual attention is best illustrated by the cocktail-party effect?

a. ambiguity

b. constancy

c. adaptation

d. selectivity*

72%, .41. At a cocktail party or similar gathering, we tend to focus on the person we're talkingto, and "tune out" other voices and conversations. We don't process every bit of auditorystimulation that falls on our ears, and every bit of visual stimulation that falls on our eyes. Rather, we can actively select what aspects of the stimulus environment we're going toattend to, and which we're going to ignore. This isn't a matter of habituation, or adaptationto some level of stimulation. The person we're talking to can be talking very softly, whileeveryone else in the room is talking loudly. It's a matter of selective attention.

Retain this exam, along with a record of your answers.

A provisional answer key will be posted to the course website by3:00 PM today.

The exam will be provisionally scored to identify and eliminate baditems.

The exam will then be rescored with bad items keyed correct for allresponses.

Grades will be posted to the course website.

A final, revised, answer key, and analyses of the exam items,

will be posted on the course website when grades are posted.

Requests for rescoring must be received within one (1) week of theposting of grades