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What did Plato believe about the senses and perception?
senses are deceiving us
our senses only detect the mere shadows of what is true
Allegory of the Cave
senses are shadows of reality and can’t be trusted
can only know true forms that structure our world through reason
Theory of Forms
perfect ideas/forms exist in separate realm of perfect forms
can only be discovered by reason
souls are fragments of cosmos-soul
we have the knowledge within us, we just need to recover it
What did Aristotle believe about sensation/perception?
form is just the organization of matter
cannot be form w/o matter and vice versa
no separate immaterial soul that lives independent of matter
What is rationalism? Who was rationalist?
belief that knowledge is primarily gained through reason and logical thought
independent of sensory experience
Rene Descartes → “i think therefore i am”
What did Rene Descartes think about perception?
superiority of deductive reasoning over inductive reasoning
drawing conclusions from specific premises (e.g. all humans are mortal, socrates was human, therefore socrates was mortal, etc.)
What is empiricism? Who were famous empiricists?
belief that knowledge comes primarily from sensory experience and observation of the world
John Locke & David Hume
What was Locke’s theory of ideas?
info from senses enters mind as “simple ideas”
e.g. “blue” + “triangle”
simple ideas then assemble to form complex ideas
e.g. = “blue triangle”
What did David Hume believe?
took empiricism to extreme → inference of necessary cause and effect is invalid
but we psychologically believe there is cause and effect
beliefs are caused by psychological “habits”
e.g. sun has risen every day, therefore expect it should rise tmrw
What did Immanuel Kant believe?
mix of both empiricism & rationalism
Critique of Pure Reason
certain concepts exist independently from sensory experience
may never know thing itself (noumenon)
all we can know is the impression the Noumenon exerts on senses (phenomenon)
minds contribute innate knowledge (a priori structures) in order to make sense of our sensations
3 a priori structures:
time
space
causality
What did Weber discover about perception?
discovered just-noticeable difference
What is the just-noticeable difference/difference threshold?
smallest noticeable difference that someone can perceive
JND is perceptually equivalent
1g diff between 40-41g feels the same as 10 gram diff between 400-410g
What is a weber fraction?
for weight: JND always close to 1/40 (0.025) of standard weight
for other stimuli fraction is different but always a fraction
Sensory Dimension | Weber Fraction |
Touch (vibration) | 0.04 |
Taste | 0.2 |
Smell | 0.07 |
Loudness | 0.3 |
Pitch | 0.003 |
Brightness | 0.08 |
Length of lines | 0.001 |
What is discriminability?
how easy is it to notice a small difference in terms of physical intensity
High Weber Fraction = Low Discriminability
Who was Fechner? What did he believe/discover?
suffered eye dmg from staring at sun then got depressed (wtf weirdo)
vision came back and he became spiritual and started learning abt mind
believed in panpsychism
created “Fechner’s equation”
What is Panpsychism?
refers to idea that everything material has mental aspect
reality 1 piece, but has 2 aspects (material & mental)
What is Fechner’s law equation?
p=k\cdot log(\frac S{S_0})
p represents subjective perception (experience)
S represents the physical intensity of the stimulus
S_0 the smallest intensity of the stimulus that can be perceived, or absolute threshold
k is a modality-specific factor controlling the steepness of the function depending on the sensory modality.
[Grows logarithmically]
What are the three steps of sensation and perception?
[after feeling physical stimulus]
transduction
transmission/modulation
perception/modulation
What is tranduction?
physical stimulus interacts with specific receptor located on peripheral sensory neuron → causes neuron to fire
stimulus is transduced into electrical signal
action potentials occur to pass on info
How do sensory receptors respond to temperature? Mint/Chili?
different sensory receptors respond to different temperatures
CMR = cold stimuli
VR = hot stimuli
certain chemicals activate certain sensory receptors
why certain chemicals feel hot/cold
Menthol → activates CMR (cold) stimuli
makes mint feel cold
Capsaicin → activates VR1 (heat) stimuli
makes chili peppers feel hot
What is transmission/modulation?
neural signal is transmitted through central nervous system through cranial nerves
for somatosensation it enters spinal chord through PNS
peripheral neurons send signals to CNS through synapse
signal is sent to thalamus (relay center)
Modulation: brain has capacity to modulate (increase/decrease) signal from peripheral sensory neurons
e.g. during sleep thalamus modulates and completely blocks almost all sensory info to the brain
What is perception/modulation?
perception occurs when sensory signal reaches the cortex
signal is sent from thalamus to primary sensory cortices (and then association cortices)
these are necessary for perception but not sufficient
What did Stanley Smith Stevens do/research?
how much more/less intense are 2 stimuli of different intensities
discovered that different sensory modalities have different shapes (pain → exponential shape)
can perceive smaller differences in pain at higher intensities
psy(I)=kI^a
psy: subjective percept
I: stimulus intensity
a: controls curvature of function
k: corrects for scaling of measurement units for I
What is magnitude rating?
rating the magnitude/intensity of a stimulus on a scale (visual analog scale)
scale has both extremes (one end = no pain, other end = worst pain imaginable)
where does the shock fall
In order to compare perception of stimulus between other people, used cross-modality matching
can use the general labeled magnitude scale
What is the general labeled magnitude scale? (GLM scale)
used for cross modality matching
has multiple sensory modalities on scale
How can visual analog scale and GLM scale be used? Which should be used for comparing stimuli within one person vs multiple?
analog scale better for comparing diff stimuli in 1 individual
GLM scale better for comparing same stimuli across different people
What is the detection threshold?
smallest stimulus intensity that can be detected at least 50% of the time
threshold is probabilistic
What is thresholding?
technique used to identify JND/diff threshold and detection threshold
can be measured in diff ways
method of constant stimuli
method of limits
staircasing method
What is the method of constant stimuli?
sample range of pre-defined intensities for stimulus
stimulus intensities presented at random until every stimulus been presented 10 times
record when they say yes/no + plot
most accurate but takes most amount of time
What is method of limits for thresholding?
start very high/low and increase or decrease until there’s reversal (until they finally detect or stop detecting stimulus)
What is the staircase method for thresholding?
start very high/low and increase/decrease until reversal
then move onto next stimulus at similar intensity and increase/decrease until reversal
least amount of time but least accurate
![<p>$$p=k\cdot log(\frac S{S_0})$$</p><p>$$p$$ represents subjective perception (experience)</p><p>$$S$$ represents the physical intensity of the stimulus</p><p>$$S_0$$ the smallest intensity of the stimulus that can be perceived, or absolute threshold</p><p>$$k$$ is a modality-specific factor controlling the steepness of the function depending on the sensory modality.</p><p></p><p>[Grows <strong>logarithmically</strong>]</p>](https://knowt-user-attachments.s3.amazonaws.com/9b625f7d-77ba-4164-8ce3-b873a0934ed9.png)
