Introduction
Welcome to our world
Sensation = ability to detect (a pressure on your back…) and perhaps turn that detection into a private
experience
Perception = the act of giving meaning and/or purpose to those detected sensations (how do you
understand the finger that runs down your back? Affection? Officer looking for weapons?)
Method 1: Thresholds
Faintest sound you can hear? Loudest (safely)? Listen too loud not able to hear the faintest sound
you could before threshold has changed. How would you measure thresholds like this?
Method 2: Scaling – measuring private experience
You hear/taste something are those xpces the same as another person’s? No direct way to xpce
someone else’s differences. Can’t really know if different people’s qualitative xpces are the same.
Method 3: Signal detection theory – measuring difficult decisions
Perceptual decision made by an expert real consequences (ex: radiologist). Signal detection theory
how decisions of this sort can be studied scientifically.
Method 4: Sensory neuroscience
How does the pepper fool your nervous system into thinking that your tongue is on fire? Ways in
which sensory receptors & nerves undergird your perceptual experience.
Method 5: Neuroimaging – an image of the mind
Binocular rivalry (face/house: 1 different stimulus for each eye) two images compete to dominate
your perception (alternate, not seen together). Represents a dissociation between the stimuli & your
private perceptual xpce. We can’t share the xpce but brain-imaging techniques see traces of that
xpce as it takes place in the brain.
Thresholds & the dawn of psychophysics
Fechner. Debate: dualism/materialism. Dualism mind = separate from material world of the body.
Materialism mind is not separate. Modern materialist position = the mind is what the brain does.
Fechner aimed to describe relationship sensation (mind) // energy (matter) that gave rise to that
sensation. He called both his methods and his theory psychophysics (mind & matter). He thought it
would be possible to do it using mathematics.
Psychophysics = science of defining quantitative relationships btwn physical & psychological (subjective)
events.
Weber: used a device to measure the smallest distance btwn two points that is required for a person to
feel touch on two distinct points tested accuracy of sense of touch. This distance = ‘two-point touch
threshold’.
Difference threshold = smallest change in a stimulus that can be detected. For every measure, a
constant ratio btwn the change and what was being changed can describe the threshold of the
detectable change (weight: 1/40, length of lines: 1/10…) Weber fractions. Fechner found here a way
to describe the relationship btwn mind and matter. Fechner: difference threshold is a unit of the mind (it
is the smallest bit of change that is perceived). He created Weber’s law and Fechner’s law (w/ maths).
Welcome to our world
Sensation = ability to detect (a pressure on your back…) and perhaps turn that detection into a private
experience
Perception = the act of giving meaning and/or purpose to those detected sensations (how do you
understand the finger that runs down your back? Affection? Officer looking for weapons?)
Method 1: Thresholds
Faintest sound you can hear? Loudest (safely)? Listen too loud not able to hear the faintest sound
you could before threshold has changed. How would you measure thresholds like this?
Method 2: Scaling – measuring private experience
You hear/taste something are those xpces the same as another person’s? No direct way to xpce
someone else’s differences. Can’t really know if different people’s qualitative xpces are the same.
Method 3: Signal detection theory – measuring difficult decisions
Perceptual decision made by an expert real consequences (ex: radiologist). Signal detection theory
how decisions of this sort can be studied scientifically.
Method 4: Sensory neuroscience
How does the pepper fool your nervous system into thinking that your tongue is on fire? Ways in
which sensory receptors & nerves undergird your perceptual experience.
Method 5: Neuroimaging – an image of the mind
Binocular rivalry (face/house: 1 different stimulus for each eye) two images compete to dominate
your perception (alternate, not seen together). Represents a dissociation between the stimuli & your
private perceptual xpce. We can’t share the xpce but brain-imaging techniques see traces of that
xpce as it takes place in the brain.
Thresholds & the dawn of psychophysics
Fechner. Debate: dualism/materialism. Dualism mind = separate from material world of the body.
Materialism mind is not separate. Modern materialist position = the mind is what the brain does.
Fechner aimed to describe relationship sensation (mind) // energy (matter) that gave rise to that
sensation. He called both his methods and his theory psychophysics (mind & matter). He thought it
would be possible to do it using mathematics.
Psychophysics = science of defining quantitative relationships btwn physical & psychological (subjective)
events.
Weber: used a device to measure the smallest distance btwn two points that is required for a person to
feel touch on two distinct points tested accuracy of sense of touch. This distance = ‘two-point touch
threshold’.
Difference threshold = smallest change in a stimulus that can be detected. For every measure, a
constant ratio btwn the change and what was being changed can describe the threshold of the
detectable change (weight: 1/40, length of lines: 1/10…) Weber fractions. Fechner found here a way
to describe the relationship btwn mind and matter. Fechner: difference threshold is a unit of the mind (it
is the smallest bit of change that is perceived). He created Weber’s law and Fechner’s law (w/ maths).
