Study Guide for Psychology Exam #2
Sensation and Perception
Chapter Summary: How do we sense our worlds?
∙ Stimuli must be coded to be understood by the brain:
o Stimuli reaching the receptors are converted to neural impulses through the process of transduction.
∙ Psychophysics relates stimulus to response:
o By studying how people respond to different sensory levels, scientists can determine thresholds and perceived change (based on signal detection theory). Our sensory systems are turned to both adapt to constant levels of stimulation and detect changes in our environment.
o Signal detection theory:signal detection theory is a means to quantify the ability to discern between information-bearing patterns (called stimulus in humans, signal in machines) and random patterns that distract from the information (called noise, consisting of background stimuli and random activity of the detection machine and of the nervous system of the operator).
What are the basic sensory processes?
∙ In taste, taste buds detect chemicals: Don't forget about the age old question of How many intellectual subfields are there in anthropology?
o The gustatory sense uses taste buds to respond to the chemical substances that produce at least five basic sensations: sweet, sour, salty, bitter, and umami (savory). The number and distribution of taste buds vary among individuals (cultural taste preferences begin in the womb).
∙ In smell, the nasal cavity gather odorants: Don't forget about the age old question of Sodexo was founded in what country?
o Receptors in the olfactory epithelium respond to chemicals and send signals to the olfactory bulb, in the brain. Females are much more accurate than males at detecting and identifying odors.
∙ In touch, sensors in the skin detect pressure, temperature, and pain:
o The haptic sense relies on tactile stimulation to activate receptors for temperature, for sharp and dull pain, and for other sensations. Neural “gates” in the spinal cord also control pain. We can reduce pain perception by distraction, visualizing pain as more
pleasant, being rested and relaxed, learning how to change brain activity that underlies pain perception, and taking drugs that interfere with the neural transmission of pain or render us unconscious.
∙ In hearing, the ear detects sounds waves:
o The size and shape of sounds waves activate in different hair cells in the inner ear. The receptors’responses depend on the sounds waves’frequency and timing and on the activated receptors’ location along the basilar membrane. Having two ears allows us to locate the source of a sound.
∙ In vision, the eye detects light waves:
o Receptors (rods and cones) in the retina detect different forms of light waves. The lens helps the eye focus the stimulation on the retina for near versus far objects. Color is We also discuss several other topics like Who are leonor michaelis and maud menten?
determined by wavelengths of light, which activate certain types of cones; by the absorption of wavelengths by objects; or by the mixing of wavelengths of light. ∙ Humans and animals have other sensory systems: Don't forget about the age old question of What is the solution to the problem of habitat loss?
o In addition to the five basic senses, humans and other animals have a kinesthetic sense (ability to judge where one’s limbs are in space) and vestibular sense (ability to compare one’s bodily position to the upright position). Some animals can use sound waves or disruptions in an electrical field to navigate.
∙ The evidence for extrasensory perception (ESP) is weak or nonexistent:
o Little or no good evidence supports the intriguing idea that some people have additional sensory systems that allow them to know what other people are thinking, for example, or to see through objects.
What are the basic perceptual processes?
∙ Perception occurs in the brain:
o Neural activity in the primary auditory cortex gives rise to hearing. Touch is mediated by neural activity in the primary somatosensory cortex. Vision results from a complex series of events in various areas of the brain but primarily in the occipital lobe.
∙ Object perception requires construction:
o The Gestalt principles of stimulus organization account for some of the brain’s perceptions of the world. Those perceptions involvecues about similarity,
proximity, form, figure and background properties, and shading. Perception If you want to learn more check out It is a type of forecasting method that involves examining today's forecast scenario and remembering a day in the past when the weather scenario looked very similar. what is it?
involves dual processes: bottom-up (sensory information) and top-down We also discuss several other topics like What organ of the urinary system that produces and secretes urine?
(expectations about what we will perceive)
∙ Depth Perception is important for locating objects:
o An object’s pattern of stimulation on each of the two retinas (binocular) informs the brain about depth. The brain uses pictorial (monocular) cues –information about the object’s appearance relative to the surroundings –to perceive depth and relative motion.
∙ Culture influences perception:
o People raised in a carpentered world –who have interacted with carpentered structures – are more prone to illusions based on cues such a linear perspective than are people raised in a non-carpentered world.
∙ Size Perception has internal and external cues:
o Illusions of size can be created when the retinal size conflicts with the known size of objects in the visual field, as in the Ames, Ponzo, and moon illusions.
∙ Motion Perception has internal and external cues:
o Motion detectors in the cortex respond to stimulation. The perceptual system establishes a stable frame of reference and relates objects movement to it.
Motion aftereffects, which are opposite in motion from things that have been
observed, tell us about the fatigue of receptors that are fire in response to
motion in certain directions.
∙ Perceptual Constancies are based on ratio relationships:
o We created expectancies about the world that allow us to use information about the shape, size, color, and lightness of objects in their surroundings to
∙ Additive Color mixing: When lights of different wavelengths are mixed, what you see is determined by the interaction of these wavelengths within the eye’s receptors. ∙ Subtractive Color mixing: A way to produce a given spectral pattern in which the mixture occurs within the stimulus itself and is actually a physical, not psychological, process.
∙ Audition: The sense of sound perception (aka hearing).
∙ Binocular Depth Cues: Cues of depth perception that arise from the fact that people have two eyes.
∙ Monocular Depth cues: Cues of depth perception that are available to each eye alone. ∙ Bottom-up processing: A hierarchal model of pattern recognition in which data are relayed from one processing level to the next, always moving to a higher level of processing.
∙ Top-down processing:A hierarchicalmodel of pattern recognition in which information at higherlevel of processing can also influence lower, “earlier” level in the processing hierarchy.
∙ Cones: Retinal cells that respond to higher level of illumination and result in color perception.
∙ Rods: Retinal cells that respond to low levels of illumination and result in black-and white perception.
∙ Cornea: The clear outer covering of the eye.
∙ Retina: The thin inner surface of the back of the eyeball. The retina contains the photoreceptors that transduce light into neural signals.
∙ Eardrum (tympanic membrane): A thin membrane, which sounds waves vibrate, that marks the beginning of the middle ear.
∙ Fovea: The center of the retina, where cones are densely packed.
∙ Gustation: The sense of taste.
∙ Haptic sense: The sense of touch
∙ Iris: The colored muscular circle on the surface of the eye; it changes shape to let in more or less light.
∙ Kinesthetic sense: Perception of our limbs in space.
∙ Lateral inhibition: A visual process in which adjacent photoreceptors tend to inhibit one another.
∙ Olfaction: The sense of smell, which occurs when receptors in the nose respond to chemicals.
∙ Olfactory epithelium: The thin layer of tissue, within the nasal cavity, that is embedded with smell receptors.
∙ Olfactory bulb:the brain center for smell, located below the frontal lobes.
∙ Perception: The processing, organization, and interpretation of sensory signals; it results in an internal representation of the stimulus.
∙ Sensation:the sense organs’responses to external stimuli and the transmission of these responses to the brain.
∙ Transduction: A process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation.
∙ Perceptual constancy: People correctly perceive objects as constantin their shape, size, color, and lightness, despite raw sensory data that could mislead perception.
∙ Pupil: The small opening in the eye; it lets in light waves.
∙ Receptive Field: The region of visual space to which neurons in the primary visual cortex are sensitive.
∙ Sensory Adaption: Is a decrease in sensitivity to a constant level of stimulation. So because of sensory adaption, people who live near constant noise (like by an airport) eventually become less aware of the noise.
∙ Signal Detection Theory: states that detecting a stimulus requires making a judgement about its presence or absence, based on subjective interpretation of ambiguous information.
∙ Sound Wave: The pattern of the changesin air pressure through time that results in the percept of a sound.
∙ Taste Buds: Sensory receptors that transduce taste information.
∙ Vestibular Sense: Perception of Balance.
∙ Gestalt Principles:Gestalt psychology describes how perceived features of a visual scene are grouped into organized wholes.
Notes from the Lecture on Sensation and Perception
Each sensory system has Active vs. Passive abilities
∙ Active- organism can be active in seeking info (finding something).
∙ Passive- detect something around yourself (example being you can feel a fly on your shoulder before you swat it away).
Phasic vs. Tonic abilities
∙ An example of a tonic receptor is a pain receptor. Once it gets stimulated, it sends a signal along the nerves to the brain as long as the pain stimulus continues.
∙ A Pacinian corpuscle is an example of a phasic receptor. It is sensitive to vibrations and pressure and thus can detect different textures. A similar example is the Golgi-Mazzoni corpuscle, which is a phasic receptor located on the fingertips. Phasic is a stimuli that means change. Types of energy that humans can sense:
1. Mechanical (auditory)
2. Electromagnetic (vision) visible spectrum
3. Thermal (somatosensory) heat/cold
4. Chemical (taste/smell)
Stimulus- intensity + quality of physical energy. Intensity is measured in photons. Light stimulus is defined in terms of:
1. Intensity (number of photons)
2. Wavelengths(450-700 nm can be perceived by humans).
Psychophysics- how you relate physical qualities of energy to psychological.
Absolute thresholds- lowest amount of energy that can be detected on 50% of trial. An absolute threshold is the lowest detectable stimulus.
1. Example for hearing would taking participants and setting up a clock and seeing which participant heard the clock ticking-their absolutely thresholds for hearing usually depends on how old they are.
2. In vision, the absolute threshold refers to the smallest level of light that a participant can detect. For example, determining the absolute threshold for vision might involve measuring the distance at which a participant can detect the presence of a candle flame in the dark. In one classic experiment, researchers found that after controlling for dark adaptation, wavelength, location and stimulus size, the human eye was able to detect a stimulus of 90 photons.
3. For odors, the absolute threshold involves the smallest concentration that a participant is able to smell. An example of this would be to measure what the smallest amount of perfume that a subject is able to smell in a large room.
∙ Difference threshold- just noticeable difference (JND): the minimal difference in some stimulus dimension needed to tell two stimuli apart
∙ Weber’s law- how to figure out difference between stimuli. Historically important psychological law quantifying the perception of change in a given stimulus. The law states that the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus.
3 components of each sensory system:
1. Supportive structures
2. Receptors (biological transducers): physical energy into language of the nervous system-the movement of ions across membranes. Example would be that a phone transduces electrical into digital. Transduction requires absorption of energy.
3. Neural Structures- Muller’s Doctrine: evokes sensation associated with vision- doesn’t matter how or where you stimulate, it will be appropriate for that system. Law of Projection- will appear to originate in the periphery (in the world).
a. Phantom limb-sensation of limb still being there despite being cut off.
b. Visual system- 450-700 nm; measured in photons (as stated before)
∙ Intensity- Brightness
∙ Wavelength- Hue
∙ Mix of Wavelengths- Saturation
∙ Physical energy- Psychological Response
∙ Pastels- unsaturated
∙ Theory says we have two kinds of vision- night and day vision. The particular receptors in your retina are your rods (high sensitivity at night- low levels of illumination, can’t read in the dark) and receptors responsible for day vision are cones. At night you’re achromatic, you don’t see color. Rod connected to many bipolar cells, high degree of convergence and divergence to bipolar cells. If you can see colors, you’re using your cones. Three different kinds of cones with different sensitivities.
∙ Rod-cone break shows the rods kicking in- adjusting from extreme light to extreme dark. Born without rods, suffer from night blindness- can’t see in the dark at all. All pieces of evidence for the duplicity theory (we see with two kinds of visions). Fovea has a lot of acuity but lacks sensitivity.
∙ Cones are in both regions but rods are only in the periphery
∙ Rhodopsin- visual purple. Purple combo of short and long wave lengths. Can’t have sensation without absorption. You can’t see a color with just a single photopigment. When rhodopsin absorbs and photon, it breaks down into two compounds- opsin and retinal.
∙ Receptive field: part of body that excites the neuron is the region of the receptor surface or from what the receptors see that excites the neuron
∙ Eustachian tube-tube in which fills with air and goes out to your sinuses. Allows pressure to be equalized
∙ Cochlea is the hearing apparatus and the vestibular apparatus controls balance ∙ Supportive Structures cont:
o The fluid-filled inner ear: the cochlea (hearing) and vestibular apparatus (balance). o oval window: transmit pressure from middle to inner ear
o round window:release of pressure
o Basilar membrane: location of receptors (hair cells).
How is loudness coded? : By the amplitude of vibrations of basilar membrane. This determines how hard hair cells are pulled.
Perception Lecture Notes
The perceptual system is stunningly intelligent in its ability to guide each of us around. Right this minute, your brain is making millions of calculations to produce a coherent experience of your environment. Your experience is a construction of your brain.
From the thalamus, information from each sense is projected to a specific region of the cerebral cortex. In these primary sensory areas, the perceptual process begins in earnest.
1. Auditory neurons in the thalamus extend their axons to the primary auditory cortex, which is in the temporal lobe.
2. Touch information from the thalamus is projected to the primary somatosensory cortex, which is in the parietal lobe.
3. The study of perception has focused to a large extent on the visual cortex and the multiple areas in which the retinal image is processed. The primary visual cortex is located in the occipital lobe. Object agnosia- meaning the inability to recognize objects (mistaking your coat rack to be your wife and greeting it hello).
∙ Gestalt means “shape” or “form”, but as used in psychology, it means “organized whole”. ∙ The principle of proximity statesthat the closer two figures are to each other, the more likely we are to group them and see them as part of the same object.
∙ Principle of similarity shows that we tend to group figures according to how closely they resemble each other, whether in shape, color, or orientation.
∙ Good continuation is the tendency to interpret intersecting lines as continuous ratherthan as changing direction radically.
∙ Illusory contours, which refers to the fact that we perceive contours (boundary lines) even though they do not exist. Illusory contours appear when stimulus configurations suggest that contours oughtto be present.
∙ Reversible figure illusion-in which we see either a full face or two faces looking at each other – but not both at the same time. In identifying either figure –indeed any figure –the brain assigns the rest of the scene to the background.
∙ This effect(thatcher illusion) implies that we pay most attention to the eyes and mouth; as long as they are oriented correctly, the rest of the face appears normal even if it is not. ∙ One of the visual system’s most important tasks is to locate objects in space. Without this capacity, we would find it difficult to navigate in and interact with the world.
∙ We are able to perceive depth in these two-dimensional patterns because the brain applies the same rules or mechanisms that it uses to work out the spatial relations between objects in the three-dimensional world.
∙ Occlusion: a near objects occludes (blocks) an object that is farther away
∙ Relative size:far-off objects project a smaller retinal image than close objects do ∙ Familiar size: we know how large familiar objects are, so we can tell how far away they are by the size of their retinal images.
∙ Linear perspective: parallel lines appear to converge in the distance.
∙ Texture gradient: as a uniformly textured surface recedes, its texture continuously becomes denser.
∙ Position relative to horizon: all else being equal, objects below the horizon that appear higher in the visual field are perceived as being father away. Objects above the horizon that appear lower in the visual field are perceived as being father away.
Summing up Perception
All perception occurs in the brain. Information first carries in primary sensory regions, such as V1 for vision and A1 for audition, but multiple brain regions contribute to our unified perceptual experience. The perceptual system uses cues from the person’s environment to help interpret sensory information.
Summing up Learning:
∙ Much of what has been learned supports Hebb’s theory that neurons that fire together wire together. Kandel’s work on aplysia has shown that habituation and sensitization, two simple forms of learning, occur through alteration in neurotransmitter release. The discovery of long term potentiation shows that intense stimulation of neurons can strengthen synapses, increasing the likelihood that one neuron’s activation will increase the firing of other neurons in the network.
∙ Associative learning-two kinds of learning classical conditioning: instrumental conditioning. Classical conditioning works through pairing of unconditioned stimulus and conditioned stimulus.
∙ Second order conditioning- process by which a neutral develops the ability to elicit a conditioned response after being paired only with a conditioned stimulus.
Example: Tone (CS) --- Food (UCS) >>> drool (UCR).
Tone (CS)>>> drool (CR)
∙ Tone was the conditioned stimulus and thus created the conditioned response of drool because the person associates the tone with being fed.
∙ What causes conditioning- Contiguous means next two each other. Temporal contiguity means that things happens together in time. The conditioned response will not appear if they do not overlap the food and tone.
1. Classically conditioned aversion: Watson and “little baby Albert”- Watson wanted to show that children are born without innate fear. He took the baby and introduced a rat to him-the child wasn’t afraid. The next time the child is introduced the rat, Watson clashes a pair of cymbals. Now the child associates the rat with the scary, loud noise. He also associated that fear with the color white, the technician, anything that the child saw in the room, he began to associate those things with that fear.
2. Taste aversion and the Garcia Effect: How does the taste aversion happen? Garcia studied rats and found that if you take a rat and offer him some new food and then make them sick right afterwards- after that one experience of eating and become sick, the rat will no longer want to eat the food.
The contiguity of the two things made the rat and baby Albert avoid the things they associated with their bad experience. The unconscious nature of classical conditioning: the above aversions, fears, phobias, and conditioned hypertension
∙ Operant conditioning: Organism “operates” on the environment- actively manipulating their environment (if you hadn’t typed on the computer, the words would have appeared)
• Reinforcement is contingent on correct behavior- Reinforcement (m&m in the mouth if you do a certain thing would be reinforcement
• Thorndike and the “law of effect”: when a reward immediately follows a behavior, that behavior is strengthened (Get an itch, scratch it, you are rewarded with that relief).
• Cat in “puzzle box”- put cat in a cage and there was a latch that the cat could operate to open the door so they were no longer trapped. Eventually after wandering around the box, the cat accidentally hit the latch and are freed. This repeated until the cat finding the latch becomes quicker and they associate hitting that latch with being freed-known as trial and error learning. • “Trial and error learning”
• “S” shaped learning curve-the cat learning about the latch takes a while and slowly becomes better until they reach a point where they understand immediately that if they hit the latch, they are freed. This learning behavior is in the shape of an “S”.
• Mostly voluntary behavior using skeletal muscles
∙ Reinforcers: stimuli which, when they follow a behavior, act to increase the probability of the behavior.
• Positive Reinforcement: stimulus in which you add itto a behavior (m&m when you do the desired behavior)
• Negative Reinforcement: loud obnoxious tone added- bar allows you to turn it off. The tone was negative
• Punishers: stimuli which, when they follow a behavior, act to decrease the probability of the behavior (goes to reach for cookies, someone knocks it out of your hand, no longer going to go for the cookies)
B.F. Skinner and S-R psychology. Used all positive reinforcement
• Reaction to “mentalisitic” notions of cognitive psychology. Why does the rat expect food? Because it was reinforced that it was going to receive food as long as it performed a certain action. • Focus on careful measurements of rates of responding
• Developed the “Skinner box” (pigeon in Skinner box, there was pigeon food) Performed this experiment on his own child. Easy to test how the subject reacted to certain reinforcements. • Very useful practical applications that are used in “behavioral therapy”
• Much use of positive reinforcement
• “Shaping” of behavior through successive approximations. Clear end goal in mind, how do you get to end goal? A pot maker shapes the clay slowly to reach the end goal of whatever idea they had in their head-steps bring you closer to the approximation that you want.
How do you shape behavior through successive approximations?
o Find a good primary reinforcer (primary needs are being met, such as eating and having sex) and a good secondary (conditioned) reinforcer- for a person this would be praising the person for the act that they accomplished. They realize that doing this action will let them receive praise.
o Wait for behavior to be emitted and reinforce behaviors that approach the desired behavior.
Instrumental conditioning- animal is instrumental to changing the environment. B.F. Skinner believed in positive reinforcement and shaping the behavior through successive approximations.
How to shape behavior through successive approximations:
o find primary reinforcer and a good secondary (conditioned) reinforcer. You wait for the behavior to be emitted and reinforce behaviors that approach the
o In very small steps, increase the demand. The demand is the condition in which you give reinforcement-reinforcement only occurs when the desired behavior is emitted.
What would serve as a positive reinforcer?
1. For example, the professor can be reinforced by the students positive reaction to his lecture (interested looks, paying attention). From this you can manipulate how the professor moves- he goes in one direction, you make a positive face. When he goes in a direction that you don’t want him to, you act disinterested. From this the teacher moves in such a way that depends on his students faces and he acts upon the student’s desired behavior in order to get that positive reinforcement.
2. Another example would be sounding a buzzer when an animal faces the direction that you want it to and then give it some food. Eventually, as the animals nears the object you want it to interact with and sounding the buzzer as it gets closer, the buzzer becomes a positive reinforcement. You successively are shaping the behavior of the rat. This method is great for training people and other animals.
Partial Reinforcement and schedules of reinforcement
There doesn’t always have to be a reinforcement. If we get a reinforcement every once in a while, we can get different outcomes.
Partial reinforcement: hard to extinguish- acquiring the correct response takes longer to get
1. Fixed Ratio schedule- high rates; pause after reinforcement; “piece rate”. Schedule reinforcement talks about the relationship between doing the correct behavior and the reinforcement. Fixed Ratio schedule- Fixed number of times you have to do something to get reinforcement-the ratio is fixed and doesn’t change. Fixed ratio tend to have very high rates to respond- person tends to take a break after receiving their reinforcement- piece rate is like when you have to produce a certain about of pieces in order to get a dollar
2. Variable ratio schedule- high rates; no pauses; gambling, very hard to extinguish. The ratio varies- you generate high rates because on average you have to work quite a bit for the reinforcer, but there are no pauses. This is the same schedule that people work on when at the casino (gambling). This is an addictive process (hardest ratio to extinguish) although the payout (reinforcer) usually does not outweigh the work that is put in.
3. Fixed Interval schedule- means after you get a reinforcement, a certain interval of time passes. It doesn’t matter how many times you press that bar, you won’t get a reinforcement. You have to wait for the interval amount of time to pass to press the bar in order to receive the reinforcement. Pause after reinforcement; scallop like response; checking the mail (you wait for the anticipated mail to come the next day- after an appropriate amount of time passes until you try again for the reinforcement).
4. Variable interval schedules-high rates, no pauses; calling back when line is busy Punishment
•Suppresses but does not extinguish undesirable behavior- Punishment is when you deliver a stimulation to a behavior and intend to decrease that behavior. An example would be that your dog is jumping up on the table and so you give the dog a whack on the nose as punishment to show that the behavior is undesirable. Can be physical and conditioned punishments. An example of conditioned
punishment would be asking your professor a question and the professor mockingly responding, “You don’t know that?”
•People who are punished more tend to be punishers in the future. Punishment CAN suppress behavior. But this doesn’t mean that the behavior completely stops-the “punished” learns to stop doing the behavior in front of the “punisher” (cat learns to scratch furniture when the owner isn’t around).
May sometimes be useful to suppress an undesirable behavior long enough for positive reinforcement to shape a new, competing behavior. Take the “punished” away from the behavior that they’re doing and then showing them what they should be doing.
Some side effects
1. Often elicits emotional responses that are incompatible with learning new behaviors. You may become embarrassed from being punished in class and you can’t focus on the material anymore 2. Negative effects may generalize to persons delivering the punishment or the entire situation- if a child is punished too much is school, they end up disliking school altogether. 3. Complex (Non-associative) learning
4. Characterized by “sudden understanding” or insight. A very insightful solution the problem, not a slow trial and error solution to the problem. Not an “S” shaped learning curve o Insight learning- Kohler, the mentality of apes 1925. The multiple stick problem (monkey learns that he needs one stick to reach the other, longer stick in order to reach the banana).
∙ Latentlearning: learning develops with time, not with continued reinforcements (you sleep on it and realize what the solution is when you wake up).
∙ Development of “cognitive maps” of the environment.
∙ Observational learning (Bandura)-learning that occurs when watching the behavior of others and then mocking that behavior (theorized by Albert Bandura).