Lec 1/ TB Ch 1

Question 1

• Sensation
• Perception
• Condillac & senses
• 5 methods to study senses
• 1 approach to study senses

Answer 1

• Sensation: ability to detect a stimulus, and turn that detection into a private experience
• Perception: act of giving meaning to a detected sensation
  
  • Ex. “finger run down the back”
    
    • Is this affection or officer looking for dangerous objects?
• Etienne Condillac – philosopher
  
  • our mental life depends on info from our sense
• Methods used to study senses
• Method 1: Thresholds
  
  • Measure how sensitive your senses are
    
    • Ex. What is the loudest sound you can hear safely?
    • If you blast loud music, your threshold will change (bad)
• Method 2: Scaling – measure private experience
  
  • Qualia: private conscious experiences of sensation/perception
    
    • Ex. what you hear, taste
  • We don’t have a direct way to experiences others’ experiences
  • We can show that diff ppl have diff sensory worlds
• Method 3: signal detection theory – measuring difficult decision
  
  • Ex. Radiologist look at X-ray to screen for cancer
    
    • If it is cancer, and R missed it -> patient dies sooner
    • If it is not cancer, and R said it is -> family is worried
• Method 4: sensory nro
  
  • There are sensory receptors and nerves that support perceptual experience
  • Ex. hot peppers smell nice and have a complex initial flavor
  • Then, you feel a burning sensation in your mouth even though the temperature in your mouth is constant
  • The pepper fools your NS to think your tongue is on fire
• Method 5: Neuroimaging – an image of the mind
  
  • Ex. each eye sees diff pic (L = house; R = face)
    
    • Binocular rivalry: when you are looking at 2 images w/ diff eyes, the 2 images will compete to dominate your perception
    • Ex. sometimes you see a house; sometimes a face; but you never see the 2 images together
    • This is a dissociation b/w stimuli presented to your eye and your own perceptual experiences
  • Neuroimaging helps us see the experience when it happens in the brain
• Development
  
  • The study of changes over the life span
  • Approach to study sensation and perception; not a method

Question 2

• Nativism
  
  • Definition
  • Supporter
• Empiricism
• Dualism/mind-body dualism
  
  • Definition
  • Supporter
• Monism
  
  • definition
  • 2 forms of monism
• How empiricism came about - 3 steps
  
  • Hobbes view
  • Lcoke’s view
• Is empiricism accurate?
• POV from modern scientists

Answer 2

Nativism and Empiricism

• Nativism: The idea that the mind produces ideas that are not derived from external sources (innate)
  
  • Plato: supports nativism
  • Believes we are born with knowledge of reality, it is in our mind and soul
  • Dualism: both mind and body exist
    
    • Mind–body dualism: spirit/soul and matter/body are two distinct principles of being/substances in the universe
      
      • Descartes: supports dualism
      • Also found in Eastern philosophy
• Monism: the mind and matter are formed from a single ultimate substance or principle of being
  
  • Found in European, Indian, and Chinese philosophy
  • 2 forms of monism
    
    • Idealism: reality is a mental construct closely connected to ideas.
      
      • Our reality came from a mental construct
    • Materialism: physical matter is the only reality, and everything including the mind can be explained in with matter and physical phenomena.
      
      • Our reality and mind came from matter
• How empiricism came about:
  
  • 1 Nativism: Mind is not made of external sources (matter); there is a soul.
  • 2 Materialists: Mind is made of physical matter; there is NO soul
  • 3 Materialists proposed Empiricism
    
    • Empiricism: experience from the senses is the only source of knowledge (learnt)
    • Hobbes: all that is known or imagined is learnt through our senses
    • Locke: all thoughts are constructed from experience, with a collection of sensations
• MP: Empiricism is extreme and incorrect (ex. behaviourism)
  
  • We can learn to fear bunnies and spiders
  • It’s more difficult to fear bunnies
  • This suggests there is more than learnt behaviour
• Most scientists today are materialists
  
  • They believe the mind is made of physical matter; there is NO soul
  • This physical matter is your genes

Question 3

• Founder of experimental psych
• What is Fechner’s argument for the dualism and materialism debate?
• Psychophysics
• Weber
  
  • 2-point threshold
  • Judgement of lifted weight experiment
  • Just noticeable difference (JND)/ difference threshold
  • Exception to JND
  • Weber’s Law/fraction
  • Fechner’s law
  • Absolute threshold

Answer 3

• Gustav Fechner is the actual founder of experimental psych
• Philosophical debate at his time: dualism vs materialism
  
  • Fechner proposed the idea – panpsychism
  • Panpsychism: the mind/conscience is present in all living and non-living things - all matter has consciousness
• He thinks mental life and physical world can be related
  
  • Psychophysics: the science of defining quantitative relationships b/w physical and psych (subjective) events
    
    • it is possible to describe the relation b/w mind and body w/ math
    • he wants to describe the relationship b/w mind and energy (matter) that give rise to sensation
• Weber – studied touch
  
  • 2-point touch threshold: the minimum distance b/w 2 points for a person to feel that the 2 points are separate (rather than as one point)
  • Judgement of lifted weight
    
    • Ppl lift one standard weight (a weight that stayed the same over the experimental trials) and comparison weight (differ from standard weight)
    • Weber increased the comparison weight incrementally over the trials
    • Results: the ability of a person to detect the difference b/w the standard and comparison weight depend on the standard weight
      
      • If the standard weight was relatively light, ppl are better at detecting a small diff when they lifted a comparison weight
      • If the standard weight was heavier, ppl needed a bigger diff to detect a change
    • Just noticeable difference (JND)/ difference threshold: the smallest detectable difference b/w 2 stimuli
      
      • IOW: the minimum change in a stimulus that allows it to be correctly judged as diff from a reference stimulus
  • JNDs changes systematically
    
    • Smallest change in weight that can be detected = 1:40 of standard weight
      
      • Ex. we can detect 1g change if the standard weight is 40g
      • Ex. we can detect 10g change if standard weight is 400g
    • JNDs for lengths of 2 lines = 1:100
    • other stimuli (ex. brightness, pitch, time) also have JND ratios
    • Exception: when the stimuli is very small or very large, nearing the max/min of our senses
  • Fechner gave a math formula for Weber’s observations
  • Weber’s Law: JND (or Weber’s fraction) is a constant proportion of the stimulus intensity level
  • ΔI ∝ I -> ΔI = k x I
    
    • ΔI = the size of detectable difference
    • k = Weber fraction, the constant of proportions
    • I = level of stimulus
• Fechner applied Weber’s law to describe the relationship b/w mind and matter
  
  • ΔI can be a unit of the mind, the smallest bit change that is perceivable
• Fechner’s law: describes the relationship b/w stimulus and sensation
  
  • subjective sensation is proportional to the log of stimulus intensity
  • S = k log I (actually: S = k log I/I0)
    
    • S: psychological sensation
    • I: physical stimulus level, intensity
    • k: constant
  • • As the stimulus intensity (R) increases, larger changes are needed for the changes to be detected by the perceiver (S)
  • When stimulus increases, our subjective sensation increases then plateaus
  • • The book makes a distinction b/w physical properties and subjective sensation/perception
  • Ex. physical intensity of sound = dB; subjective sensation = loudness
  • Ex. physical oscillation of sound = frequency; subjective perception = pitch
  • The physical and subjective measurements are not the same, but are correlated
• Fechner’s methods are used today
  
  • Absolute threshold: the min intensity of a stimulus that can be detected 50% of the time
• Examples for absolute threshold & JND:
  
  • ticking watch at different distances
    
    • Absolute threshold: watch is 200m away, you can’t even hear it
    • JND: 2 watches, one is clearly louder; you can tell
• When does Fechner’s law holds true?
  
  • For weight, brightness, vacation time (1^st day of vacation feel long, last day passes by too fast)

Question 4

Psychophysical Methods

• Which 3 did Fechner develop?
• Which 2 did Steven’s dev?
• Method of Constant stimuli
  
  • Version 1: absolute threshold
    
    • 3 steps
    • cons
  • Version 2: JND
    
    • 3 steps
  • Detection task to determine the absolute threshold
    
    • Methods
    • Floor ceiling effect
  • JND version
    
    • Methods
    • What is 0.84 on the curve

Answer 4

Psychophysical Methods

• Fechner developed
  
  • Method of constant stimuli
  • Method of limits
  • Method of adjustment
    
    • Stevens developed
      
      • Magnitude estimation
      • Cross-modality matching
    • Fechner and some dude in the 1950s?
      
      • Signal Detection Theory
• 1. Method of constant stimuli
     * Version 1: - Absolute threshold(tiniest intensity that can be detected)
     * 1. Create many stimuli w/ diff intensities (from rarely to always perceivable)
     * 2. Present the stimuli and one at a time to ppl in a random order; the stimuli were presented multiple times at each intensity
     
     • Need to present multiple times b/c the stimulus may be perceived differently due to the subject’s attention/ sensory system changes
  • 3. Ppl report if they detect the stimuli
       * most ppl can detect stimuli that are far abv threshold
       * Occasionally, they report detecting stimuli that is below threshold
  • Our NS constantly changes, and stimuli near the threshold are detected or missed
  • So, Absolute threshold is an arbitrary boundary, not a sharp change b/w I detect (ex. hear) it vs I don’t
  • Cons: inefficient b/c the subject spends a lot of time w/ stimuli that are clearly well abv or below threshold
• Version 2: - JND
  
  • Rs create many stimuli that range from “rarely perceivably different” to “almost always perceivably different” from a standard stimulus
  • Rs presented two in each trial.
  • Each time participants state which of the two stimuli is [heavier/brighter/more blue/happier…]
• Ex. Detection task to determine the absolute threshold
  
  • 1. Rs prepare 30 shades of blue
  • 2. Rs present one shade of blue to ppl and ask “do you see blue?”; repeat this for several trials
  • X-axis: physical intensity (ex. 30 shades blue saturation)
  • Floor-ceiling effect:
    
    • Floor: you can’t detect smth all the time (ex. there’s no blue)
    • Ceiling: you can always detect smth all the time (ex. there’s always blue)
• Ex. Detection task to determine the JND
  
  • 1. Rs prepare 30 shades of blue
  • 2. Rs present 2 shades of blue to ppl and ask “which blue is more saturated?”; repeat this for several trials
       * Each trial, you see a standard stimulus & probe
       *
       * Then you repeat it…
       *
  • X-axis: difference saturation
    
    • Left: standard stimulus and probe are very similar
    • Right: standard stimulus and probe are clearly different
  • JND: project a line from 0.5 and another line from 0.84 (y-axis)
    
    • We use 0.84 b/c it is 1SD away from 0.5
    • By convention, we define JND as 1SD away
    • Green curve: shows a person who has poorer color perception
      
      • 0.5 line is the same
      • 0.84 line is projected further down the x-axis
      • Here, the JND is larger
      • This means you need a huger contrast b/w the standard stimulus and probe to detect a difference
• 2. Method of limits – difference b/w 2 stimuli is changed incrementally until the subject responds differently
     * More efficient approach
     * Uses stimuli that vary in intensity (ex. tones that vary in intensity)
     * Present stimuli/tones in ORDER of increasing or decreasing intensity
     
     • Ex. tones
       
       • Ascending = faintest to loudest
       • Ppl report when they first hear the tone
       • Descending = vv
       • Ppl report when the tone is no longer audible
         
         • There is “overshoot” in judgement
     • It takes more intensity to report hearing the tone when the intensity is increasing
     • It takes more decreases in intensity for a listener to report the tone can’t be heard
       * Solution to determine the threshold: avg the crossover points
     • Crossover point: When listeners shift from reporting hearing the tone to not hearing the tone
     • • 3. Method of adjustment – subject controls the change in stimulus
            * Similar to method of limits
            * The subject steadily increases or decreases the intensity of the stimulus
     • Similar to adjusting the volume dial on a stereo/ dimmer switch for light
       * Not often used b/c the data is messy
     • The same person will adjust the dial to diff places and diff trials

Scaling Methods –

• Understand how strong your experiences are
• Magnitude estimation: ppl assign values based on their perceived magnitudes of the stimuli (invented by Stevens)
  
  • Example w/ sugar solutions
  • 1. Give them a series of sugar solutions
  • 2. Present a solution at an intermediate lv, and label this level as a specific value (ex. 10)
  • 3. Ask them assign #s to remaining solution that are scaled on the standard of 10
       * Sweeter solutions = bigger #s
       * If Sol A is 2x sweeter to sol B; Sol A = 10; Sol B = 5
  • You get a “sweetness” line
  • IOW: you can assign #s to private experiences, and the results are still orderly and lawful
  • They may differ for each type of sensation
  • Steven’s power law
    
    • S = aI^b
      
      • S = sensation
      • I = stimulus intensity
      • b = exponent
      • a = constant
  • Keep units consistent
  • If exponent b > 1 (ex. 2), the experienced sensation grows rapidly w/ stimulus
  • If exponent b < 1, sensation grows less rapidly than stimulus
  • Ex. if you have 1 candle and add 10 more, the change seems dramatic
  • Ex. if you have 100 candles and added 10 more, the change is modest
  • Ex. If you have 10k candles and add 10 more, the change is unnoticeable
  • Exponent for brightness = 0.3
  • Exponent for sweetness = 0.8
  • Exponent for shock = 3.5 (I^3.5)
    
    • 4^3.5 = 128
    • IOW: increase from 1 to 4 volts is perceived as 128 times more painful
  • Exponent for length (and a bunch of other things) = 1
    
    • IOW: 12-inch stick looks 2x longer than 6-inch
    • This relationship is only true for moderate range of sizes
      
      • Ex. add 1 inch to spider changes your sensation more than add 1 inch to giraffe
  • Applies to plants and animals
    
    • Ex. Flower w/ 2 units of sugar has more adv than flower w/ 1 unit
    • Ex. Flower w/ 12 units of sugar doesn’t hv as much adv over flower w/ 11 units -> Bees can’t detect this difference
    • Ex. Peacock w/ 51 feathers doesn’t have that much adv over peacocks w/ 50 feathers -> peahen doesn’t see the diff
• Weber vs Fechner vs Steven
  
  • Weber’s law: ΔI = k x I
    
    • ΔI = size of detectable difference; k = constant; I = lv of stimulus
    • objective measurement
    • We know how much rs changed the stimulus
    • We know if the observers can tell the stimulus changed or not
  • Fechner’s law: S = k log R
    
    • S = subjective sensation; R = physical stimulus intensity; k = constant
    • Objective measurement
    • This assumes all just noticeable differences are perceived the same
    • Some cases violate this law, electrical shock
      
      • increase from 1 to 4 volts is perceived as 128 times more painful
      • increase from 1 to 4 inch is perceived as 4 times longer
  • Steven’s power law: S = aI^b
    
    • S = sensation; I = stimulus intensity
    • b = exponent; a = constant
    • Based on self-report ratings
    • These ratings can be reasonable and consistent
    • But we do not know if these ratings are objectively correct or not
• Cross-modality matching
  
  • Another scaling method
  • Refers to the ability to match the intensities of sensations that come from different sensory modalities
    
    • Ex. Ask listener to adjust brightness of light until it matches the loudness of a particular tone
    • Ppl w/ “normal” visions and hearing produce same pattern of matches of a sounds to light
  • Provide insight on sensory differences
  • Cons: Can’t examine ppl’s private experience
  • Exception: taste
    
    • Propylthiouracil (PROP): a molecule that some find very bitter, some find tasteless, and others fall in b/w
  • Marks et al 1988
    
    • Examined PROP test using cross-modality matching
    • Observers match bitterness of PROP to other sensations unrelated to taste
    • Here, we don’t see agreement that is seen when observers match sounds to light
    • Nontasters – match the PROP taste to weak sensations (ex. sound of watch/whisper)
    • Supertasters: match PROP taste to the intense sensations (ex. sun’s brightness/ intense pain)
      
      • Experience more oral burn and oral touch
    • Medium tasters – match PROP taste to moderate sensations (ex. smell of frying bacon/ pain of mild headache)
    • This is due to genetics
  • Main point: scaling methods help quantify real differences in indiv taste experiences

Question 5

Psychophysical Methods cont 2

• Method of limits
  
  • Definition
  • Overshoot
  • Crossover point
  • Ex. Blue color task
• Method of adjustment
• Scaling methods
  
  • Magnitude estimation
  • Cross-modality matching
    
    • Definition
    • Marks et al 1988 - Examined PROP test using cross-modality matching
  • Stevens asked ppl to assign values according to perceived magnitudes of stimuli to measure sensation.
    
    • 3 main results
    • Steven’s power law

Answer 5

• 2. Method of limits – difference b/w 2 stimuli is changed incrementally until the subject responds differently
     * More efficient approach
     * Uses stimuli that vary in intensity (ex. tones that vary in intensity)
     * Present stimuli/tones in ORDER of increasing or decreasing intensity
     
     • Ex. tones
       
       • Ascending = faintest to loudest
       • Ppl report when they first hear the tone
       • Descending = vv
       • Ppl report when the tone is no longer audible
         
         • There is “overshoot” in judgement
     • It takes more intensity to report hearing the tone when the intensity is increasing
     • It takes more decreases in intensity for a listener to report the tone can’t be heard
       * Solution to determine the threshold: avg the crossover points
     • Crossover point: When listeners shift from reporting hearing the tone to not hearing the tone
• Ex. Blue color task
  
  • Each row = a trial
  • Trial 1
    
    • 1. Trial 1 – show ppl a very blue color (intensity @ 20), and ask “do you see blue?”; repeat w/ increment of blue
    • 2. If the person says “No, can’t see blue”, you stop trial 1
         * Trial 2
         
         • 1. Star w/ a very faded blue (intensity @ 10), and ask “do you see blue?”; repeat w/ increment of blue
         • 2. If the person says “Yes, I see blue”, you stop trial 2
              
              • You do 8 runs, and then average across where they switch “from yes to no” and “no to yes” -> this produces the absolute threshold
• 3. Method of adjustment – subject controls the change in stimulus
     * Similar to method of limits
     * The subject steadily increases or decreases the intensity of the stimulus
     
     • Similar to adjusting the volume dial on a stereo/ dimmer switch for light
       * Not often used b/c the data is messy
     • The same person will adjust the dial to diff places and diff trials

Scaling Methods –

• Understand how strong your experiences are
• Magnitude estimation: ppl assign values based on their perceived magnitudes of the stimuli (invented by Stevens)
• Ex. Your GP asks: On a scale of 1-10, how painful is your headache?
• Magnitude estimation is a quick and direct way to measure subjective sensation (S)
• Magnitude estimation varies between people, but is consistent w/in each person (ex. headache rating)
  
  • Example w/ sugar solutions
  • 1. Give them a series of sugar solutions
  • 2. Present a solution at an intermediate lv, and label this level as a specific value (ex. 10)
  • 3. Ask them assign #s to remaining solution that are scaled on the standard of 10
       * Sweeter solutions = bigger #s
       * If Sol A is 2x sweeter to sol B; Sol A = 10; Sol B = 5
  • You get a “sweetness” line
  • IOW: you can assign #s to private experiences, and the results are still orderly and lawful
  • They may differ for each type of sensation
• Cross-modality matching
  
  • Another scaling method
  • Refers to the ability to match the intensities of sensations that come from different sensory modalities
    
    • Ex. Ask listener to adjust brightness of light until it matches the loudness of a particular tone
    • Ppl w/ “normal” visions and hearing produce same pattern of matches of a sounds to light
  • Provide insight on sensory differences
  • Cons: Can’t examine ppl’s private experience
  • Exception: taste
    
    • Propylthiouracil (PROP): a molecule that some find very bitter, some find tasteless, and others fall in b/w
  • Marks et al 1988
    
    • Examined PROP test using cross-modality matching
    • Observers match bitterness of PROP to other sensations unrelated to taste
    • Here, we don’t see agreement that is seen when observers match sounds to light
    • Nontasters – match the PROP taste to weak sensations (ex. sound of watch/whisper)
    • Supertasters: match PROP taste to the intense sensations (ex. sun’s brightness/ intense pain)
      
      • Experience more oral burn and oral touch
    • Medium tasters – match PROP taste to moderate sensations (ex. smell of frying bacon/ pain of mild headache)
    • This is due to genetics
  • Main point: scaling methods help quantify real differences in indiv taste experiences
• Stevens asked ppl to assign values according to perceived magnitudes of stimuli to measure sensation.
  
  • Results: there are exceptions to Fechner’s law
  • Brightness follows a log curve; follow Fechner’s law
  • Apparent length (linear) and electrical shock (exponential) are exceptions
• Steven’s power law
  
  • S = aI^b
    
    • S = sensation
    • I = stimulus intensity
    • b = exponent
    • a = constant
• Steven aims to capture more cases (log, linear, and exponential)
  
  • If b < 1 -> log curve
  • If b = 1 -> linear
  • If b > 1 -> exponential
• Ex. if you have 1 candle and add 10 more, the change seems dramatic
• Ex. if you have 100 candles and added 10 more, the change is modest
• Ex. If you have 10k candles and add 10 more, the change is unnoticeable
• Exponent for brightness = 0.3
• Exponent for sweetness = 0.8
• Exponent for shock = 3.5 (I^3.5)
  
  • 4^3.5 = 128
  • IOW: increase from 1 to 4 volts is perceived as 128 times more painful
• Exponent for length (and a bunch of other things) = 1
  
  • IOW: 12-inch stick looks 2x longer than 6-inch
  • This relationship is only true for moderate range of sizes
    
    • Ex. add 1 inch to spider changes your sensation more than add 1 inch to giraffe
  • • Weber vs Fechner vs Steven
  • Weber’s law: ΔI = k x I
    
    • ΔI = size of detectable difference; k = constant; I = lv of stimulus
    • objective measurement
    • We know how much rs changed the stimulus
    • We know if the observers can tell the stimulus changed or not
  • Fechner’s law: S = k log R
    
    • S = subjective sensation; R = physical stimulus intensity; k = constant
    • Objective measurement
    • This assumes all just noticeable differences are perceived the same
    • Some cases violate this law, electrical shock
      
      • increase from 1 to 4 volts is perceived as 128 times more painful
      • increase from 1 to 4 inch is perceived as 4 times longer
  • Steven’s power law: S = aI^b
    
    • S = sensation; I = stimulus intensity
    • b = exponent; a = constant
    • Based on self-report ratings
    • These ratings can be reasonable and consistent
    • But we do not know if these ratings are objectively correct or not

Question 6

Psychophysical Methods cont 3

• signal detection theory
  
  • Noise
    
    • internal
    • External noise
  • Ex. Snoopy shower-and-phone situation
    
    • Signal
    • Noise
    • Methods - 3 steps
    • How to determine
      
      • hit rate
      • false alarm rate
      • sensitivity
  • Define sensitivity
  • How to determine bias
  • 3 factors that influence bias

Answer 6

Signal Detection Theory

• The stimulus you detect (i.e. signal) is detected in the presence of “noise”
  
  • Ex. You are in a quiet rm w/ noise-cancelling headphones; you can still hear some noise
  • Ex. you close your eyes in a dark rm, you still see grey patches and some bright flashes
• This internal noise comes from the NS
  
  • As you approach your threshold, is come hard to tell apart a real stimulus from internal noise
• External noise
  
  • Ex. radiologist read mammogram to look for signs of breast cancer
  • Fuzzy white = cancer
  • But there are other similar regions that look like cancer
  • Cancer = signal
  • Mammogram = contains signal (cancer) and noise
  • Sometimes, both external and internal noise are so small that you cannot detect real impact (ex. very little internal and external noise around “a”)
• Ex. shower time
  
  • 1. The phone rings
       * Signal = Phone ring
       * Noise = shower
  • 2. We want to know how good is Snoopy’s hearing
       * 6 trials there is NO phone call
       * 6 trials there is phone call
       * Snoopy can respond
       
       • “I think I hear the phone”
       • “I don’t think I hear a phone”
  • 3. The 4 possible outcomes
       * 1. Correct rejection: You say “no” when there is no ringtone
       * 2. Hit: you say “yes” when there is a ringtone
       * 3. False alarm: you say “yes” when there is no ringtone
       * 4. Miss: you say “no” when there is a ringtone
       * * Sensitivity: the ease w/ which an observer can tell the diff b/w presence and absence of a stimulus OR diff b/w Stimulus 1 and 2
• Sensitivity is related to the signal to noise ratio
  
  • There’s either internal or external noise
    
    • External noise: the shower is loud; the phone ring is soft
    • Internal noise: the neurons not as efficient at sending signals
      
      • Observers can have high or low sensitivity (Internal)
        
        • Ex. Snoopy has ear plugs vs no
        • Ex. Snoopy vs human
      • easy vs difficult situation (external)
        
        • Ex. Phone ring is weak; shower is loud
• Biases
  
  • unbiased observer
    
    • Check: each row adds up to the # of trials (6 trials)
      
      • biased observer (2 types)
        
        • conservative & liberal/ risk-taking

What influences biases?

• Costs of decisions
  
  • Ex. You have an important phone call for a job interview
    
    • Is stepping out of the shower vs missing a phone call more costly?
• Probability of events (phone calls)
  
  • Ex. It’s 6AM; it is unlikely ppl will call -> you become more conservative
• Personality: conservative vs risk taking personality

Question 7

• What is ROC
• What does black line mean
• What does the red line mean
• Which scenarios are biased
• What can the signal detection theory separate based on this graph

Answer 7

• Received Operating characteristics (ROC)
  
  • plot false alarms (x-axis) w/ hits (y-axis)
  • Scenarios 1,2,3,4 are along the black line
    
    • This means there are no biases in these scenarios
    • Check: each row adds up to the # of trials (6 trials)
  • Scenarios 5,6 are along the red line (not on black)
    
    • This indicates they are biased
  • NOTE: if you slide left or right on each curve; this indicates bias (ex. green dot)
• You can see that Signal detection theory separates sensitivity (signal vs noise) from biases (liberal vs conservative)
  *

Question 8

• What is Fourier Analysis - process
• Period
• Wavelength
• Amplitude
• Phase
• Frequency
• What can produce pure sounds waves
  *

Answer 8

• Fourier analysis:
  
  • any signal can be separated into component sine waves at different frequencies
  • Combining these sine waves will reproduce the original signal
• This analysis helps better describe how complex sounds, motions, and images can be decomposed into a set of simpler components
• Sound
  
  • Period: time taken for 1 complete cycle of sine wave OR wavelength to pass a point
  • Wavelength: distance for 1 full cycle of oscillation for a sine wave
  • Amplitude: height of the wave
  • Phase: its position relative to a fixed marker
    
    • Measure in degrees
    • 1 period = 360 degrees (or 2π)
    • Ex. red and blue sine waves differ by 90 degrees in phase
    • • Frequency: (for a wave) # of cycles per second
  • Most sounds in the world cannot produce pure sound waves, they produce complex sounds
  • Exception: tuning forks, notes from flute
  • Complex sounds can be described using sine waves; This applies to a room full of ppl talking, full orchestras
• Vision
  
  • Can use Fourier analysis to understand vision
  • Air: change in pressure over time
  • Images: changes in light and dark across space
  • We can break down images into components to capture how often changes from light to dark occur in a specific area
  • Spatial frequency: the # of light/dark changes (i.e. grating) across 1 degree of a person’s visual field
  • Cycles per degree: unit of spatial frequency
    
    • The # of light-dark bars pairs (cycles of grating) per degree of visual angle
    • There’s 360 degrees around our head
  • The space b/w dark-light stripes in A has 2x the spatial frequency of B
    
    • • When spatial frequency (i.e A and B) are represented in sine waves, there are more amplitude differences for high contrast (C), than low constrast (D)
    • • How things will look like when high frequencies are removed (F) vs low frequencies removed (G)
  • • Visual stimulus (like complex sounds) can be broken down into component spatial frequencies

Many neurons hv strong preference for some frequency components over others, esp during early stages of auditory and visual processing

Question 9

• What does Darwin’s evolution theory suggest
• Muller’s doctrine of specific nerve energies
• 12 pairs of cranial nerves
  
  • What do they do
  • 12 cranial nerves
    
    • 3 sensory info
    • 3 eye movements
    • 2 motor info
    • 4 sensory and motor

Answer 9

Sensory Neuroscience and the Biology of Perception

• Darwin’s theory of evolution: argues humans and apes evolve from a common ancestor
  
  • IOW, we can learn about human sensation and perception by studying he structure and function of animals
• Muller’s doctrine of specific nerve energies: the nature of sensation depends on which nerves are stimulated rather than how they are stimulated
  
  • Ex. We experience vision b/c the optic nerve is stimulated, it doesn’t matter if it is light or pressure from pressing your eyes stimulated the nerve
• 12 pairs of cranial nerves
  
  • Come from the brain stem and reach sense organs and muscles; they pass through small openings at the base of the skull
    
    • Dedicated to sensory and motor systems
  • Sensory info cranial nerves
    
    • Olfactory (I) – smell
    • Optic (II) - sight
    • Vestibulocochlear (VIII)
  • Eye movements
    
    • Oculomotor (III)
    • Trochlear (IV)
    • Abducens (VI)
  • Motor info
    
    • Spinal accessory (XI)
    • Hypoglossal (XII)
  • Motor and sensory info
    
    • Trigeminal (V)
    • Facial (VII)
    • Glossopharyngeal (IX)
    • Vagus (X)
• (O, O, O, To Touch And Feel A Girl’s V, Ah Heaven)

Question 10

• Sensory
  
  • How does olfactory (I) work
  • How does optic (II) work
  • Vestibulocochlear (VIII)
    
    • fx
    • what 2 things it connects?
• Eyes
  
  • Oculomotor (III)
    
    • What eye muscles does it control
  • Trochlear (IV)
    
    • Which muscle?
  • Abducens (VI)
    
    • Which muscle?
• Motor
  
  • Spinal accessory (XI)
    
    • Which muscle?
  • Hypoglossal (XII)
    
    • Which muscle?
• Motor and sensory info
  
  • Trigeminal (V)
    
    • which muscle?
    • sensory
  • Facial (VII)
    
    • Which muscle?
    • sensory
  • Glossopharyngeal (IX)
    
    • Which muscle?
  • Vagus (X)
    
    • Which muscle?

Answer 10

• Sensory
  
  • Olfactory (I) – smell
    
    • Axons of olfactory sensory neurons bundle together after passing thru the cribriform plate to form the olfactory nerve
    • The nerve conducts impulses from olfactory epithelia in the nose to the olfactory bulb
  • Optic (II) - sight
    
    • Come from retina and carry visual info to the thalamus and other areas
  • Vestibulocochlear (VIII)
    
    • Balance (spatial orientation) & hearing (name)
      
      • Connects inner ear w/ brain
      • Composed of the cochlear and vestibular nerve branch
• Eye movements
  
  • Oculomotor (III)
    
    • All eye muscles except lateral rectus and superior oblique muscles
    • Controls elevator muscle for upper eyelid, ciliary muscle, and sphincter muscle for the pupil
  • Trochlear (IV) – control superior oblique muscles for eyeballs
  • Abducens (VI) – control lateral rectus muscle for eyeballs
• Motor info
  
  • Spinal accessory (XI)
    
    • Sternomastoid muscle
    • Trapezoid muscle
  • Hypoglossal (XII) – glossal = tongue muscle
• Motor and sensory info
  
  • Trigeminal (V) – face, sinus, teeth
    
    • muscle = jaw
  • Facial (VII) – Tongue & soft palate
    
    • muscle = face
  • Glossopharyngeal (IX)
    
    • Posterior tongue
    • Tonsils (see pic above)
    • Pharynx
    • • Pharyngeal muscles
  • Vagus (X)
    
    • Heart, lungs, GI tract, bronchi, trachea, larynx

Question 11

• Warmth and cold fibers
• Capsaicin and menthol - what are they
• Ointments w/ capsaicin or menthol - what can it do?
• Cortex
  
  • Motor cortex - 4 cortices, 3fx
  • Define polysensory
  • Muller’s vitalism
  • Helmholtz view & experiment

Answer 11

• doctrine of specific nerve energies applies to other areas
  
  • Warmth and cold fibers: respond to increase in decrease temp on skin
  • Capsaicin and menthol
    
    • Capsaicin: chemical found in chili peppers, stimulate warmth fibers
      
      • Feel increase heat even though temp has not changed
    • Menthol: chemical found in minty cough drops, stimulate cold fibers
      
      • Skin feels colder w/o getting physically colder
    • In high doses, both chemicals can stimulate pain receptors on the skin
      
      • Ointments w/ capsaicin or menthol masks real physical pain
• Diff brain areas and their tasks
  
  • Lobes: FL, temporal lobe, parietal lobe, occipital lobe
  • 4 primary sensory cortices:
    
    • Somatosensory cortex – skin senses
    • Visual cortex
    • Auditory cortex
    • Olfactory cortex
  • Motor cortex: balance, touch, auditory processing
• Polysensory: blending multiple sensory info; processing info beyond the primary areas
• Muller’s vitalism: idea there is a force in life that is distinct from physical entities
• Helmholtz: believes all behavior is explained only by physical laws
  
  • States vitalism violates law of conservation of energy
  • Muller thinks neurons can’t be measured experimentally
  • Helmholtz showed we can measure how fast neurons transmit their signals, and they obey physical laws
    
    • Nerves in front legs: 90 ft/s
    • Sensory nerves: 200-300 ft/s
  • Not all neurons are equal in speed

Question 12

• Cajal drawings
• Leowi finding on how neurons communicate in the synapse
• How did Hodgkin and Huxley studied action potentials - 2 steps
• APs firing and travelling - 3 steps
• How to determine what a neuron encodes for?
• Tuning curves

Answer 12

Neuronal Connections

• Cajal: made detailed drawings of neurons
  
  • The drawings suggest the neurons don’t actually touch one another; there’s tiny gaps
• Leowi
  
  • Showed that electrical waves do not travel across the synapse
  • This is b/c some neurons are excitatory, while others are inhibitory
  • Proposed chemicals NTs are used in the synapse; this allows neurons to communicate
  • Synaptic vesicles release NT from presynaptic cell’s axon terminal; NT fit into receptors on the postsynaptic cell’s dendrite
  • • Psychoactive drugs: increase or decrease effectiveness of different NT

Neural Firing: The Action Potential

• Squids have large axons that are 1mm thick
• 1 So, Hodgkin and Huxley isolated a single neuron from a squid to test how the nerve impulse travelled down the axon
• 2 They inserted electrodes in the axon to measure the voltage, and inject chemicals
• They learnt that neural firing is electrochemical
• 1. Changes in the membrane cause Na+ enter into the axon -> membrane depolarizes
• 2. Changes in the membrane pushes K+ out -> repolarize to RMP
• This happens a thousandth of a second each time a neuron fire
• 3 When on neuron is depolarized, it depolarizes the adjacent regions and recreate an AP there; this process continues down the axon until it reaches the axon terminal
• • For tiny neurons (like those in humans), the electrode is placed outside of the neuron
• To find out what a neuron encodes for, we can look at what stimulus makes it fire most vigorously
  
  • Ex. a neuron in the primary visual cortex responds most strongly to vertical lines
  • Ex. Diff neurons in the auditory nerve (from ear to brain) are sensitive to specific frequencies
• Tuning curves: show neurons are tuned to different frequencies

Question 13

• EEG
• ERP
• MEG
• CT
  
  • how does it work - 3 steps
• MRI - how it works
• fMRI - how it works
  
  • subtraction method
• PET - how it works
• Converging operation
• 3 main questions in dev approach?

Answer 13

Neuroimaging

• EEG: put electrodes on the scalp to measure electrical activity of populations of neurons
  
  • Poor spatial resolution – can’t pinpoint the exact areas of neural activity
  • Excellent temporal resolution
• ERP: measure electrical activity from a subpopulation of neurons; the average EEG after many trials
  
  • • Magnetoencephalography (MEG)
  • Similar to EEG, measures changes in magnetic activity across populations of neurons
  • Has good temporal and spatial resolution (i.e. know where in the brain neurons are most active)
  • Neurons make small change in their magnetic fields in addition to small electrical changes
  • Cons: it needs extremely sensitive devices called superconducting quantum interference devices (SQUIDS) which is $$$
• Computer tomography (CT)
  
  • Uses X-rays to create images of slices through the human body
  • 1. X-ray beams sent through the head; dense tissue absorbs more energy than lighter tissue
  • 2. Detector on the other side of the head measures the amount of energy lost on the way through the head
  • 3. This is repeated from many different positions; and these pieces of info are put together to create a 3D picture of the head
• Magnetic resonance imaging (MRI)
  
  • Use a strong magnet to influence how hydrogen atoms (from H2O) spin in the brain
  • This produces a structural image of the brain
  • This can also measure brain activity (fMRI)
• fMRI
  
  • see activity in specific brain regions
  • active neurons need more oxygenated blood
  • MRI sends magnetic pulses to detect the blood oxygen level-dependent (BOLD) signal rather than the presence of water/H atoms
  • Cons
    
    • Temporal resolution: not as good as EEG/ERP b/c it takes time for brain to be active and send BOLD signal
    • Noisy and expensive
  • Subtraction method
    
    • 1. Subject watch a visual stimulus for 30s; some brain regions are activated and demand more oxygen -> more BOLD signals
    • 2. Removed visual stimulus for 30s; brain regions are deactivated -> less BOLD signals
    • 3. Subtract “stimulus off” from “stimulus on” -> difference in BOLD signals
• Positron emission tomography (PET)
  
  • inject a radioactive oxygen tracer into subject’s bloodstream, and a camera detects gamma rays emitted from brain regions where the tracer is used the most
  • Helps locate the active neurons
  • Tracer: oxygen 15, half-life = 2 minutes
  • Pro: silent, can be used for hearing studies
  • Cons: tracer
• “converging operation”: labs use multiple methods
  
  • Ex. perform a behavioural task while being imaged

Development over the Life Span

• It is not a method; it is an approach we can take to think about sensation and perception
• 3 main questions
  
  • 1. What are be born with? – our sense
       * Bb are sensitive to faces
       * Bb prefers sweet dislikes bitter tasters
       * Bb suckling reflex relies on sense of touch
  • 2. What is learnt? - Smell
       * Sense of smell develops at the end of 1^st trimester
       * The more familiar we are w/ an odor, the more we like it
       * Ex. If mom smokes, drinks, and eats garlic; the bb prefers those smells
       * Ex. If mom eats a healthy diet; bb is open to more foods
       * Ex. bb learn that shit stinks once they are potty trained
  • 3. What changes w/ age? – senses and perception
       * Senses decline (ex. hearing, and smell)
       * Perception make be richer as we accumulate more life experience

Question 14

Early Philosophy of Perception

• Plato’s “The Allegory of the Cave”
• How is evolution and “perception and sensation” related?
• Venus fly traps
• Bees
• Snakes
• Birds
• Dolphins
• Ben underwood
• Echolocation
  *

Answer 14

Early Philosophy of Perception

Plato’s “The Allegory of the Cave” (380 BCE):

• states that our conception of reality is critically dependent on information gathered through our senses (things we perceive)
• IOW: our conception of reality is limited, and there is way much more out there
• Plato thinks: we are like prisoners, chained to a wall
  
  • All we see are the shadows and echoes of what is actually happening out there
• Perception and your sense of reality are the products of evolution:
  
  • Our perception and senses help us survival
  • The type of energy in the environment determines which senses have developed/evolved
• I.e. we might not sense the entire reality but we probably don’t need to worry too much
  
  • Ex. Venus fly traps
    
    • Venus fly traps live in dry areas
    • They supplement diet with flies
    • When a fly lands, it produces “mechanical vibrations” that trigger the “spring mechanism”
    • So, the plant closes, and the fly is trapped inside
    • The Venus fly trap doesn’t have any neurons/brains/muscles; It is the plant version of the sensory system
    • Here, the plant trap has a very limited view of reality, but its reality is relevant and important to it
    • Main point: the venus fly trap doesn’t have the senses to participate in a lecture (can’t sense entire reality)
    • That’s not a problem because it is not important to it (don’t need to worry too much)
  • Some Animals are Able to Sense Stimuli that Humans Cannot
  • Ex. Bees can see UV light; humans can’t
    
    • Flowers have UV markers, and look better under UV light
    • MP: Even though humans don’t have UV sensors, we aren’t missing out too much and can still enjoy flowers
  • Ex. Snakes see and sense infrared light to locate prey; humans can’t
    
    • Humans can’t see infrared red light, but we aren’t missing out because we can catch prey in other ways
  • Ex. Dogs have sophisticated smell and can hear ultrasound; humans can’t
    
    • Humans can’t smell or hear that well, but we aren’t missing out that much
  • Ex. Some birds can see magnetic fields to migrate; humans don’t
    
    • Humans can see magnetic fields, but we aren’t missing out much because we have devices that can do this for us
  • Ex. Dolphins and bats can do echolocation
    
    • Echolocation: they send out sounds, and detect the echoes that bounce off objects (ex. fish, injects)
    • This can help them avoid predators or catch prey
    • Ben underwood
      
      • Eyes removed at 2 yo due to cancer
      • Learnt to use echolocation:
        
        • 1. clicked his tongue
        • 2. Listen to the echoes and sense where the objects are in the env
    • MP: Most humans can’t echolocate; but we aren’t missing out much b/c we have vision to help us locate things

Question 15

Early Philosophy of Perception cont 2

• Heraclitus (540–480 BCE): “You can never step into the same river twice.”
  
  • 2 explanations
  • panta rhei - define
    
    • Explanation
    • 3 reasons
  • Adaptation - definition
  • Describe Adaptation – color task
  • Describe Adaptation – faces task
  • Describe Priming - look and don’t look task
  • Describe Adaptation – fuzzy pink ball becomes green
• Democritus (460–370 BCE): The world is made up of atoms that collide with one another
  
  • experiment
  • His view on how sensations are created
    
    • Which senses sense this way?
  • His view on perception
  • Sensory transducer

Answer 15

Heraclitus (540–480 BCE): “You can never step into the same river twice.”

• IOW: the water you step in the first time is different than the water you step in the second time
• IOW: when you step into the river the first time, you moved the water; when you into it the second time, it is not the same river
• panta rhei: everything flows
  
  • IOW: Idea that perceiver cannot perceive the same event in exactly the same manner each time
    
    • When you something the 2^nd time, you perceive in a different way than the 1^st time
  • This is because we
    
    • Can Learn from experience
    • Adaptation
      
      • Ex. We stare at a red dot, then stare at a white wall. Here, we seem to see a green dot
    • Change
      
      • Things change over time
    • Contrast
      
      • Bright vs darker sides
• Adaptation: reduction in response caused by prior or continuing stimulation
  
  • Demo 1: Adaptation – color task
    
    • 1. You stare into half blue (LS) half yellow (RS) panel
    • 
      
      • Adaptation effect:
      • Since you stared into blue (LS), your eyes then respond less intensely to blue colors on the LS
      • Since you stared into yellow (RS), your eyes then respond less intensely to yellow colors on the RS
    • 2. Then, you look into another photo and it seems to look normal
    • 3. Overtime, when the adaptation effect wears off, you notice the LS of that bb photo has more blue and the RS has more yellow
  • Demo 2: Adaptation – faces task
    
    • 1. When you look at a female face for 30s (adaptation), then look at the gender-neutral face; you tend to perceive that face as more masculine
    • ->
    • 2. When you look at a male face for 30s (adaptation), then look at the gender-neutral face; you tend to perceive that face as more feminine
    • ->
    • This shows adaption can happen at the Fusiform Face area (FFA)
  • Demo 3: Priming - look and don’t look task
    
    • 1. Group A sees an image that looks more like a mouse
         *
    • 2. Group B sees an image that looks more like a man
         *
    • 3. When both groups of people look at the “neutral” image, group A will say they see a mouse; group B will say they see a man
         *
    • MP: This shows that what we see before influences our perception later
      
      • IOW: we can’t step into the same river twice (Heraclitus)
  • Demo 4: Adaptation – fuzzy pink ball becomes green
    
    • 1. Look at the +
    • 2. At first, you see pink balls disappearing
    • 3. Then, you start to see a green ball moving around (adaptation effect)
    • MP: Nothing is permanent except change (Heraclitus)
      
      • This is true for perception: we can only perceive change; things that do not change aren’t detected
• Democritus (460–370 BCE): The world is made up of atoms that collide with one another
  
  • Experiment: he cut up a piece of wood until he can no longer further break it apart
    
    • Atom: the piece of matter that cannot be further broken down
    • Proposed that different matter is made of different atoms
  • Proposed sensations are caused by atoms leaving objects and making contact with our sense organs
    
    • Ex. You can see a screen b/c atoms from the screen travel to your eyes and interact with the atoms in your eyes
    • Now, we know this is applies to smell and taste (but not the other senses, like vision)
  • Perception: the result of the physical interaction b/w the world and our bodies
  • Sensory transducer (aka sensory receptor): A receptor that converts physical energy from the environment into neural activity