Psychophysics - Exam #1 Flashcards
What do psychological approaches focus on while studying perception?
Human judgements and observing human behavior
Who made some of the best tasks to study perception? Who came up with a lot of the tasks and paradigms that we still use today?
Psychologists!
Who were there before brain scientists?
What doesn’t the Psychological approach cover?
What leads up to perception
What does the Psychological Approach try to understand?
The relationship between an attended stimulus and a person’s perception of that stimulus
Given the scenario that a psychologist shows a picture of a car to a subject and asks them to name it, what is the name of the task that they’re being asked to do?
A Recognition/Identification Task
Give an example of a Recognition/Identification Task
Being shown a picture and being asked to name it
What is the purpose of a Recognition/Identification Task?
It’s to asses your ability to categorize a pattern of light as a category of object that you have learned
Which memory do the objects you’re being asked to identify in the Recognition/Identification Task belong in? The ones you’ve learned!
Long-term Memory!
What is the relationship between in the Recognition/Identification Task?
The physical stimulus of the light and your perception of the object (how you’re categorizing it in memory)
What is your perception of the object?
How you’re categorizing it in memory
What is more complex than a Recognition/Identification Task?
A Visual Search/Search Task
What happens in a Visual Search/Search Task?
Finding something in a cluttered visual display
Why is the Visual Search/Search Task more complex than the Recognition/Identification Task?
Now you’re not just being asked to recognize something(knowing when you’ve found something); but now you’re holding a target goal in mind of what you’re trying to find in the world (to guide your attention/eyes about where you think the target will be)
Give an example of a Visual Search/Search Task
Where’s Waldo?
What is a main part of a Visual Search/Search Task?
Where you’re allocating your attention
What kind of Perception do the Recognition and Search Tasks deal with? Why?
High-level Perception (they deal with attention and Long-term memory)
What is a Detection Task?/Example
Being asked if you can detect a pattern/letter in a field of visual noise
What is a Discrimination Task?/Example
Being asked to judge which line is longer (a difference)
What is a Magnitude Estimation Task?/Example
Being asked to compare how much brighter one circle is than another
How is the Discrimination Task and the Magnitude Estimation Task different?
In the Discrimination Task you’re being asked to chose between two choices (A or B); in the Magnitude Estimation Task you’re being asked to chose your own number based off a change (3x brighter)
Give an example of a subject response in a Magnitude Estimation Task
“The left circle is 3x brighter than the right circle”
What does the Magnitude Estimation Task show a good example of?
Human judgement in response to a stimuli
What are the Low-level Perception Tasks?
The Detection Task, Discrimination Task, and the Magnitude Estimation Task
What are Low-level Perception Tasks and Low-level Perception Research related to?
Psychophysics
What distinguishes Psychophysics from Psychology experiments?
In Psychophysics there’s a single dimension (or at least one) that can be incrementally manipulated
What is an example of something that can be incrementally manipulated in a psychophysical experiment
How much noise you add to a Detection Task; How much longer the two lines should be
What does manipulating the one dimension in a Psychophysical experiment help with?
To see how the variation in the physical form/a single physical dimension corresponds to Perception
Define Psychophysics
The study of Perception dealing with quantitative relationships between physical stimulation and perceptual experience
What does Quantitative mean? Example? (More or less)
Something that can be measured in numbers and the like (so sound pressure)
What is a Perceptual Experience? Example? Is this easy to study in numbers?
Your experience in perceiving something(not necessarily easy to measure quantitatively)–like your perception of loudness
What is the name of the relationship between you hearing someone in different loudnesses when they’re talking softer or louder? Why?
A Psychophysical relationship! The quantitative(measurable) the amplitude of the soundwaves and your perception of loudness
What may a high amplitude soundwave produce? / How may you perceive a high amplitude soundwave?
Loud!
What may a low amplitude soundwave produce? / How may you perceive a low amplitude soundwave?
Soft/Quiet!
What is Gustav Fechner (1860) the founder of?
Psychophysics!
What does the book “Elements of Physics” bring into psychology? Who wrote it?
Psychophysics! Gustav Fechner!
What is Fechner’s Law?
An equation for knowing how someone will perceive something
What did people do before Fechner’s Law?
Tedious experiments
Why is it called Fechner’s “Law”?
Because we all have the same sort of machinery
Write Fechner’s Law
S = k log l
What does the “S” stand for in Fechner’s Law?
Sensation (Which we know as Perception today)
What does the “k” stand for in Fechner’s Law?
The Weber Fraction
What does the “I” stand for in Fechner’s Law?
Stimulus intensity
What is Weber’s Fraction?
An unchanging fractional constant
What is Weber’s Fraction a measure of in Fechner’s Law?
Your ability to discriminate along a particular perceptual dimension / A measure of discriminative power
What is “I” a measure of in Fechner’s Law? How can we measure this?–What’s up with it?
The intensity of a stimulus; a number on a machine (# of photons, etc…)–A value on a machine
What is “log” on Fechner’s Law?
Log!
How did they get Weber’s Fraction?
Very tedious psychophysical experiments
What’s the point of doing super tedious psychophysical experiments?
To figure out Weber’s Fraction (what the “K” is) for different perceptual discriminations
What does a smaller Weber Fraction mean?
The more sensitive we are to a stimulus change
What scale is a Weber Fraction on?
A 0-1 scale
What are we least sensitive to a change in according to a Weber Fraction?
Salt in food
What are we most sensitive to a change in according to a Weber Fraction?
Electric Shock! We’re very efficient!
What is the relationship between the physical intensity and the psychological magnitude called?
Scaling
15:50
recording time left off!
What is a one-to-one relationship?
When you double the intensity of something and the person perceives it at twice the intensity
What is Perceptual Compression?
When the Stimulus intensity increases faster than the perceptual magnitude
What is Perceptual Expansion?
When the Perceptual Magnitude increases faster than the stimulus intensity
Give me an example of Perceptual Expansion
You get a little more electric shock, but perceive it as twice the shocky-ness
Can Perceptual Expansion be helpful?
Yes! Even if it’s just a little pain, you want to feel it more so you can stop being hurt
Can Perceptual Compression be helpful?
Yes! If you have a system with a lot of bandwith (detecting a lot in a small range like vision) It can be helpful to only feel like the light is 5x as bright instead of 10x
How can people use Fechner’s Law to help them?
To know how loud to make a horn, how bright to make a light so a pilot can see it, etc…
What is a big purpose of a detection task?
To see what the bare minimum amount of intensity is needed for perception
If an experimenter turns up the light a little bit and then asks the subject if they can see it, what kind of Task is this?
A Detection task!
What is the Method of Limits?
A way to see what the minimum amount of stimulus is for detection
How do they do an experiment for the Method of Limits?
They do it in blocks of trials–in one block they gradually increase the light to see if they can detect it, and in another they gradually decrease the light to see if they can still detect it
What is it called when a subject starts saying they can/not start seeing a stimulus?
The Crossover Point
Using the Method of Limits how do they decide where the detection threshold is?
They average all the crossover points
Define Absolute Threshold
The minimum amount of energy needed for detection by a perceptual system
What will happen if a stimulus is above the Absolute Threshold?
It will be detected
What is a Psychometric Function? What is it a part of?
A function that relates stimulus intensity (x-axis) to the subject’s detection rate (y-axis); It’s part of Classical Threshold Theory
What shape does a Psychometric Function look like in Classical Threshold Theory?
An “S”
Where is the Absolute Threshold on the graph in Classical Threshold Theory?
Where 50% of subject say “yes”
What is a/some problem/s with Classical Threshold Theory?
Common bias and minor changes in how the task was worded changed how the subjects responded
What is a Conservative Bias?
Someone who is more prone to saying “no”; they need more evidence before committing to a “yes” judgement
What is a Liberal Bias?
Someone who is more prone to saying “yes”; They don’t need a lot of evidence to commit to a “Yes”
Why are biases a problem for the Classical Threshold Theory?
The Detection Thresholds can be where a person is guessing a lot, so depending on which answer a person gives it is influenced by their bias
How does Signal Detection Theory (SDT) differ from Classical Threshold Theory?
It uses mathematical analysis of errors to separate decision factors from perceptual sensitivity–It uses math to separate a person’s bias from their perceptual sensitivity
How are Signal Detection Theory (SDT) experiments unique?
They mix signal-present with signal-absent; creating a right-and-wrong answer
What did people move to after Classical Threshold Theory?
Signal Detection Theory (SDT)
Define Signal
Activity in the perceptual system to the stimulus that you are trying to detect–Any activity in your perceptual system related to the stimulus you’re trying to detect
Define Noise
Activity in the perceptual system not correlated with the stimulus (All activity that is not the Signal)
How do people know if there’s a Signal?
If there’s multiple neurons firing for it!
Why is there Noise?
You have Neurons firing all the time; most of these are not coding for the specific patch of light in the experiment
What are the two types of Noise?
External and Internal
How can people get around the Noise? / How can Detection Performance improve?
If you increase the signal, decrease the noise, or both
What does it mean for a Noise to be Internal?
It’s coming from inside the Perceptual System (random neuron firing)
What does it mean for a Noise to be External?
It’s coming from outside the Perceptual System
How many signal-presents are there in a typical Signal Detection Experiement?
About 50% present and 50% absent
What may or may not happen in a Signal Detection Experiment on the part of the experimenter?
They may manipulate the size of the signal or the level of background noise, but this is not necessary?
What are the four types of responses in a Signal Detection Theory experiment?
A Hit, a Miss, a False Alarm, and a Correct Rejection
What is it called when someone says there’s a signal and there is?
A Hit!
What is it called when someone says there’s a signal and there isn’t?
A False Alarm!
What is it called when someone says there isn’t a signal and there isn’t?
A Correct Rejection
What is it called when someone says there isn’t a signal and there is?
A Miss
Why are Signal Detection Theory Experiments different from Classical Threshold Theory ones?
Now there’s a “correct” response
What is the only noise when you’re in a Catch Trial?
Your own Noise!
What is a Criterion?
The point in which a subject will say “yes” or “no”
What happens in a Conservative Criterion?
There will be minimal False Alarms, but a lot of misses
What happens in a Liberal Criterion?
There will be minimal Misses, but a lot of False Alarms
What does a bias NOT affect? What’s the only difference?
The separation of noise and Signal + Noise distributions; and the Probability distributions will be the same, the only difference is where their criterion is
When is detection difficult in Signal Detection Theory?
When the distributions overlap (between the signal present and the only noise)
What is Sensitivity in Signal Detection Theory?
How well you can discriminate between noise from the Signal + Noise distributions
What letter stands for Sensitivity in the Signal Detection Theory?
d’ (D prime)
What does it mean when d’ is low/zero? What does this mean for the subject?
There’s little/no sensitivity; the subject will have to guess if there’s a signal or not
What does it mean if d’ is closer to a one? What does this mean for the subject?
They are more sensitive; they’ll have an easier time detecting
What were some of the hypothesis in the Clark Napalese experiment?
Genetic differences, Napalese food may be a “pain killer”, or they all suffer a brain injury from the low oxygen
What was the Experimental Design of the Clark Napalese experiment?
Method of Limits
What was the Null Hypothesis in the Clark Napalese experiment?
There’s no difference in pain sensitivity
What is the Hypothesis in the Clark Napalese Experiment?
The Napalese are less sensitive to pain than people from Western cultures
What was the outcome of the Clark Napalese experiment? Was it consistant with their Hypothesis?
The Napalese needed more voltage to say a sitmulus was painful; consistant with their Hypothesis
What is the Formula for Sensitivity?
d’ (sensitivity) = z(Hit rate) - z(False Alarm rate)
What is the formula to see a bias?
Beta(Bias?)=ordinate(hit rate)/ordinate(False Alarm rate)
In Sensitivity What happens if the Hit rate is higher than the False Alarm rate?
The subject has some sensitivity to the task
In Sensitivity What happens if the Hit rate is the same as the False Alarm rate?
The subject has no sensitivity to the task
In Sensitivity What happens if the Hit rate is the lower than the False Alarm rate?
The subject was confused (this shouldn’t happen)
What’s the quick way to see bias in a subject in a Signal Detection Theory experiment? What does it mean?
Comparing the “yes”es and “no”es; more yes = liberal; more no = conservative
What is a quick way to see the bias if you have the Hits, False Alarms, and the Average if there’s a 50% 50% shot?
Subtract 50% from the average
What is a quick way to see the Sensitivity if you have the Hits, False Alarms, and the Average?
Subtract the False Alarms from the Hits
What is a conclusion from the Clark Napalese experiment?
Although both groups had a liberal bias, the westeners were more likely to respond that stimuli were painful compared to the Napalese–they were both equally sensitive to pain however; so the Napalese were actually just more stoic
