Lecture 11- Psychophysics

Question 1

threshold

Answer 1

in order to perceive, we must achieve a certain amount of neuronal excitation

Question 2

momentary thresholds

Answer 2

thresholds are real but exist unchanged only within a very particular moment in time

Question 3

why do thresholds shift within each person?

Answer 3

because person is responding to their environment, external and internal

Question 4

phi-gamma hypothesis

Answer 4

assumption that momentary thresholds shifts are normally distributed

Question 5

quanta

Answer 5

a photon is a “quanta” of light

Question 6

quantum mechanics

Answer 6

“how much light is in a little bit of light?”
- light behaves as a particle and a wave

Question 7

when an electron shifts from a high-energy state to a low-energy state it emits a:

Answer 7

photon

Question 8

Webers Law

Answer 8

is our physiological perception of the world PREDICTABLY different from the actual physical world?
- Just Noticeable Difference (JND)

Question 9

Webers Law

Answer 9

start with a stimulus of certain intensity, how much would I have to change that stimulus to create JND?
- how much does the physical world have to change before we can perceive that it has changed?

Question 10

Webers law

Answer 10

If there is a predictable relationship between
perception and reality, then the following should
hold true: ∆Φ= cΦ
Where ∆Φ is the change in stimulus strength
required to create a JND
- So the change required would be the intensity of
the original physical stimulus multiplied by some
constant (i.e. predictable) value “c”.
- This is known as Weber’s Law
Weber’s Law: ∆Φ= CΦ

Question 11

Gustav Fechner

Answer 11

father of psychophysics

Question 12

fechner

Answer 12

• JNDS on our ruler increase by a constant amount,
  -physical stimuli associated with these JNDS increase geometrically
• we have a way to make a ruler for perception
• 10^3= 10x10x10= 1000 -log101000= 3

Question 13

“log”

Answer 13

stands for logarithms

Question 14

Basic unit of measurement for ratio scale

Answer 14

JND

Question 15

Fechners Law

Answer 15

Ψ=k log Φ

Question 16

Ψ=

Answer 16

phi
- psychological perception of magnitude (perceived intensity of a sensation)

Question 17

k=

Answer 17

constant that changes based on modality (e.g. brightness)

Question 18

Φ=

Answer 18

actual physical magnitude

Question 19

signal detection theory

Answer 19

we perceive the world through a background of noise:
external and internal

Question 20

external noise

Answer 20

sounds, lights, smells, etc

Question 21

internal noise

Answer 21

random activation of our neurons

Question 22

there is an AVERAGE level of noise, which means,

Answer 22

there is a DISTRIBUTION of noise

Question 23

likelihood ratio

Answer 23

likelihood that a signal is actually present
- the larger the likelihood ratio, the more likely it is that a signal is present
- establish a criterion β

Question 24

if l (x) > β

Answer 24

observers decides “This came from distribution of signal plus noise, so there is a signal present”