Section 1 Flashcards
Define rationalism
the idea that we can only rely on our reason to know the world
Define empiricism
the idea that we can only rely on our senses to know the world
Was Plato a rationalist or empiricist?
Rationalist
What did Plato think senses contributed to our understanding of the world?
He thought senses provided shadows of and about reality that could not be trusted
According to Plato, what was knowing?
Knowing was a form a remembering; having all the knowledge we need, we just need to rediscover it
What is an all-knowing “cosmos-soul”?
we initially lose all memory of innate knowledge, but it can be recovered through our reason
Describe the allegory of the cave
There were three men who were chained in a cave, and the only thing they could see were shadows projected onto the wall. One of the men gets freed and realized that the shadows were only perceptions and the true things of life were being hidden from them
According to Aristotle, who disagreed with Plato’s theory of forms, what did he think forms referred to?
Organization of matter (forms are in material objects)
With respect to reason and sense, how did Aristotle understand the world?
He felt some credit must be given to our senses, that humans are built to both perceive and interact with the world to promote growth
Was Rene Descartes a rationalist or empiricist?
Rationalist
What is deductive reasoning?
You start from a known fact, and using rules of logic, combine them to form new conclusions
For deductive reasoning to provide a correct conclusion, what is required?
the premises must be valid and rules of logic must be followed
What is a problem with deductive reasoning?
The premises themselves need to be proven, which in itself may be difficult
What is inductive reasoning?
Starts from observations and comes to conclusions through a process of generalization
How did Descartes try to solve the problem of inductive reasoning?
He engaged in pre-emptive skepticism whereby he systematically tried to doubt everything that could be doubted
From the use of skepticism, Descartes made an important conclusion - what was it?
He could not rely on his senses as the only thing he could not doubt was that he could think
Was John Locke a rationalist or empiricist?
Empiricist
How did Locke understand the origin of our minds?
Humans are born as a blank slate and it is experience which develops our minds
Describe Locke’s theory of ideas
Information from our senses enters our minds as “simple ideas” which then come together to form complex ideas
According to Locke, where do simple ideas come from?
Experience
Was David Hume a rationalist or empiricist?
Empiricist
What was Hume’s focus?
He challenged how causation can be understood if everything we know must come from our senses
Did Hume’s believe cause and effect was a true concept?
No, he believed that psychologically we think that relationship exists, but really causation is an illusory belief caused by a mental habit
Describe Immanuel Kant’s theory of mind
He proposed that our minds have some form of a priori mental structure that helps us interpret sensory information
According to Kant, is it possible to take in sensory information prior to having priori strucutres?
No, priori structures need to be present before we receive sensory information from the external world
Provide three concepts that would be considered priori
Space, time, and causality
How does Kant fit in the rationalist vs empiricist ideology?
He was considered to be a critical rationalist - he believed that reason alone was not sufficient to know the world (without sensory information, priori structures lack content)
How did Ernest Weber contribute to the field of psychology as a scientific discipline?
He developed a methodology for measuring the two-point discrimination threshold
What is the Just Noticeable Difference (JND)?
the smallest change in a stimulus that can be detected
TRUE OR FALSE: the JND is always a constant fraction of the standard weight
true
if a standard weight is 500g and it takes a difference of 1g to notice a change, what would be the JND for a 1000g weight?
2g
How does the JND fit into other sensory modalities?
Every sensory modality has a fixed ratio between the JND and standard stimulus
How does discriminability relate to the weber fraction (JND/standard stimulus)?
the higher the weber fraction, the lower the discriminability
What does a weber fraction of 0.3 mean?
To discriminate between the two stimuli, the standard needs to be increased by 30%
What is the difference between the JND and weber’s fraction?
the JND is the value of the stimulus at the point where you notice a difference (e.g. 110g from 100g), whereas the weber fraction is (JND-standard stimulus)/standard stimulus (e.g. 110-100/100=10/100=0.1)
What is panpsychism?
The idea that everything material also has a mental aspect
According to Fechner, what was the mental aspect of inert things?
Our mental representation of them
Explain how based on subjective experience, each JND is perceptually equivalent
The JND between 40g and 41g is the same as the JND between 400g and 410g because since it is the smallest thing you can perceive it will subjectively feel the same regardless of the actual physical intensity of the stimulus
What does the modality factor (k) represent in Fechner’s law?
controls the steepness of the function, which is dependent on the sensory modality
How does the modality factor, k, relate to Weber’s fractions and discriminability?
directly proportional to Weber’s fraction, and has an inverse relationship to discriminability
What happens as you move further to the right on the graph for Fechner’s law?
You need to have a larger difference between the stimuli to achieve the same subjective perception (JND)
What are the four steps of perception?
- transduction
- transmission
- perception
- modulation
Describe the transduction step of perception
A physical stimulus is converted into an electrical stimulus by acting on receptors located on a peripheral sensory neuron to cause the neuron to fire
How does the firing rate of a neuron relate to stimulus intensity?
higher stimulus intensity = greater firing rate
Would the firing rate be higher or lower if the patch on your skin delivering the stimulus is small?
Higher because the stimulus is more localized
What does the nature of a sensation depend on?
Which sensory fibers are stimulated
Describe the transmission step of perception
nerve impulses travel along an axon of a peripheral sensory neuron and enter the CNS
What is the only sensory neuron that does not have their cell body in the periphery?
optic nerve
For our senses, how do sensory neurons enter the head?
through their respective cranial nerves
How does tactile and pain information reach the CNS?
through the spinal cord
Are cranial nerves sensory or motor?
Can be either one, or both
How can modulation affect transmission?
Transmission of the signal between synapses can be either facilitated or inhibited at any point
How does sleep modulation work?
sensory information is prevented from reaching the cortex at the level of the thalamus
the relationship between the thalamus and cortex is not unidirectional - which direction will you find more connections?
going from the cortex to the thalamus
When is perception thought to occur?
When the sensory information reaches its corresponding primary sensory cortex
Where is the inter-hemispheric fissure?
located in the middle of the brain to separate the two hemispheres
Where is the lateral fissure?
Separates the temporal lobe from the frontal and parietal lobes on both hemispheres
Where is the central fissure?
Starts at the lateral fissure and goes up to the inter-hemispheric fissure
What is top-down and bottom-up modulation?
top-down: higher order brain areas influence signals coming up
bottom-up: coming from the periphery to the brain
Is the primary sensory cortex enough for conscious perceptual experiences?
No, there needs to also be activity in associative cortices connected to that primary cortex
What ranking technique did Stanley Stevens create to measure stimuli?
He presented participants with a standard stimulus and assign it an arbitrary number, and then present the participant with another stimulus and ask them to rate it relative to the first - this was deemed the participant ranking technique
What is Stevens power law?
It relates subjective sensation reported by a participant to the physical intensity of the stimulus
What does the “a” exponent of Steven’s power law account for?
accounts for the different sensitivities inherently related to different stimulus modalities
What will the function look like if the a value in Steven’s power law is between 0-1? What will it look like if it is higher than 1?
If it is between 0-1 it will resemble Fechner’s logarithmic curve, but if it is greater than 1 it will become exponential (subjective sensation increases faster with higher stimulus intensities)
Why do different sensory modalities have different a values?
Not every sense requires the same sensitivity. For example, sound has an a<1 because you want to be more sensitive at low levels of intensity, but pain has an a>1 because there is no need to react strongly to very low stimulus levels such as warm water
What is absolute magnitude rating?
Participants rank a physical stimulus using a scale that goes from the lowest intensity one could perceive to the highest
What could be considered an advantage for using the absolute magnitude rating method over the participant ranking technique?
It avoids having to determine a universal unit for subjective sensation
What is cross-modality matching?
Participants rank one sensory modality using a different modality scale for which there would be no difference in sensitivity for
What is the benefit of using cross-modality matching?
Eliminates the problem of inter-individual variability whereby people will use the upper boundary of a scale differently, thus making it difficult to compare two peoples ratings
What are general label magnitude scales?
Designed to estimate the intensity of several sensations within the same scale
What does the scale look like in gLMS?
the lower boundary could be no stimulus and the upper boundary can be direct sunlight
Why is it beneficial to provide an actual sensory modality for the upper boundary rather than just worst pain imaginable?
People can think their worst imaginable pain are very different things from one another, which can make it seem as if the pain they are currently feeling is the same
What is a prothetic experience?
a sensory experience that can be associated with a number
what is a methathetic experience?
a sensory experience that cannot be described by a number
What is a difference threshold?
same as JND
Explain how the difference threshold is probalisitc
There will be a change in stimulus intensity that is expected to be perceived 50% of the time
What is an asbolute threshold?
the smallest physical intensity you can perceive - determined by the minimum amount of stimulation necessary to detect it 50% of the time
TRUE/FALSE: it is possible to have a subjective perception smaller than the absolute threshold
false
Describe the method of limits for determining the absolute threshold
You start with a stimulus intensity you know will be too low for the participant to perceive and gradually increase it until the participant perceives something. You then take the average between the last non-perceived and first perceived stimulus. You then repeat this, but this time start with a high intensity you expect them to perceive, and gradually reduce it until they no longer perceive it
In the methods of limits, ascending/descending cycles are repeated several times. Why is it done this way over just doing one cycle?
There is always a degree of randomness in our perceptions, and it is likely during the trials the point at which a participant perceives something may not actually be their threshold as if you were to continue increasing they would not perceive the next level up. Repeating several cycles increases the accuracy of the threshold value
Describe the staircase method for determining the absolute threshold
You can start at a high stimulus intensity you expect the participant to perceive, and gradually reduce it until you hit an intensity they no longer perceive. Once you find this point, you never go too far from this stimulus region. You will then start at that intensity and gradually increase until they perceive again, and then gradually reduce from that point etc.
Why would the staircase method be better than the method of limits?
Staircase method is faster, and is a bit more accurate since you never deviate too far from the likely threshold
What are two major problems in both the staircase method and method of limits?
- Participants can identify when the intensity of the stimulus is ascending or descending, which can influence their responses
- Habituation and sensitization
Describe habituation
occurs when a high intensity stimulus decreases the perception of the following one
Describe sensitization
Occurs when a high intensity stimulus increases the perception of the following one
Describe the method of constant stimuli for determining the absolute threshold
all intensities in a pre-defined range are equally sampled in a random order to avoid sequence effects
Name one advantage and one disadvantage for the method of constant stimuli
Advantage: most accurate way for obtaining an absolute threshold
Disadvantage: takes the longest to run
Describe the method of adjustment for determining the absolute threshold
Participants directly control the intensity of the stimulus, and are asked to tur the intensity of the stimulus up or down to identify the point they barely perceive anything
Which technique for determining an absolute threshold is most prone to bias?
method of adjustment
Define signal and noise
Signal: refers to the true sensory information coming from the external world
Noise: refers to whichever physiological or psychological processes that can influence our perception of that external stimulus in an unpredictable manner (anything that is not measured but contributes variability)
How can response bias affect thresholding experiments?
Some people may be more conservative in their responses such that they will withhold correct perceiving of stimulus until they are 100% sure (increases their threshold), whereas others are more liberal in that they will be quick to say they perceived something (lowers their threshold)
What is a signal detection paradigm?
Designing an experiment where you present a very faint stimulus and sometimes no stimulus at all to get an accurate sensory sensitivity regardless of participants’ response biases
Can a signal detection paradigm measure absolute thresholds?
No, it only provides a measure of how sensitive someone is
Provide a general description of signal detection theory
The analytical techniques used to infer sensitivity based on four types of responses: hit, miss, false alarm, correct rejection
Describe the four types of responses that are possible in signal detection theory
Hit: stimulus is present, participant detects it
False alarm: stimulus is absent, participant detects it
Miss: stimulus is present, participant does not detect it
Correct rejection: stimulus is absent, participant does not detect it
what kind of distribution does subjective perception follow?
normal distribution
Describe what the normal distribution looks like in signal detection theory
There are two curves, one for when a signal is present and one when it is not. The curve for a signal present usually lies further to the right. The x-axis represents the strength of the stimulus and the y-axis is the probabilty
What does the internal criterion determine?
At what strength of the stimulus you will say yes to feeling a sensation
Why does placement of the internal criterion not affect sensitivty?
Sensitivity depends on both hits and false alarms, and as you move the criterion left to right or vice versa, the proportion of hits and false alarms change in a proportional manner
Why are hits and misses related to each other?
They both make up the curve for a stimulus being present, so if your criterion is placed where hits represent 80% of yes trials, then the other 20% is attributed to misses
What is a receiver operating characteristic (ROC) curve?
Plots the probability of a hit vs false alarm
How to prepare a ROC curve?
By moving the internal criterion from right to left and plotting the probabilities of hits vs false alarms for every position of the criterion
Where on the ROC curve demonstrates the greatest accuracy?
The point that bows out the most towards the top left of the graph
Where is the internal criterion located to produce the most accurate ROC curve point?
exactly in the middle of the two peaks
Which points on a ROC curve would demonstrate the lowest accuracy? Where would the internal criterion be located?
the points at the bottom left and top right corners - represents the criterion being place completely to the right and left, respectively
If the two distributions completely overlap, what would the ROC curve look like?
linear
How does sensitivity relate to the degree of overlap of the two distributions?
The less overlap there is, the greater the sensitivity
Fill in the blanks: points that fall along the same ROC curve have the __________ (same/different) sensitivity, but ___________ (same/different) accuracy
same, different
