Chapter 1 - Scientific Methodology

Question 1

What is threshold theory?

Answer 1

Measuring detection and discrimination

Question 2

What is signal detection theory?

Answer 2

Measuring difficult decisions (psychophysics)

Question 3

What is “the black box”?

Answer 3

The time in between a sensor and an actuator that we don’t know about (i.e. what is going on between sensing and perceiving?)

Question 4

What did Gustav Fechner do?

Answer 4

• father of experimental psychology
• relationship between mind and matter
  dualism: mind and body are separate
  materialism: the mind is what the brain does
  paripsychism: the mind exists in all matter
• proposed psychophysics: relationship between physical stimuli and their subjective correlates

Question 5

What are thresholds?

Answer 5

The point of perceptual transitions

Question 6

What is detection?

Answer 6

how intense must a stimulus be in order for it to become perceived

Question 7

What is discrimination?

Answer 7

How different are two stimuli, such that we can notice the difference

Question 8

What is an absolute threshold?

Answer 8

The minimum intensity of a physical stimulus that can just be detected by an observer

Question 9

How can we measure absolute thresholds?

Answer 9

• method of adjustment: a participant observes a stimulus and adjusts its intensity until they perceive it as just detectable (record the stimulus intensity and use an estimate of absolute threshold - imprecise)
• method of constant stimuli: the participant is presented with a bank of stimuli covering a range of intensities presented in a random order (not efficient)
• staircase method: a stimulus is presented to an observer and based on their response the stimulus intensity will be increased or decreased (more precise than the first, less than the second)

Question 10

What is a psychometric function?

Answer 10

a curve that relates a measure of perceptual experience to the intensity of the physical stimulus

Question 11

What is hysteresis?

Answer 11

observer responses do not only rely on current stimulus intensity, but previous stimuli as well (the previous perceptions influence the current perception)

Question 12

What is a difference threshold?

Answer 12

(just noticeable difference)

• the minimum difference between two stimuli that allows an observer to perceive that the two stimuli are different
• estimation of JND use the same three measuring techniques

Question 13

How do we calculate the JND?

Answer 13

JND = 75%-25%/2 (result is stimulus intensity)

Question 14

What did Ernst Weber do?

Answer 14

• interested in touch
• two point touch threshold: the minimum distance where two stimuli are perceived as separate
• weight discrimination: smallest change of weight that could be detected (JND) was always 1/40 of standard weight
  
  • this law applies to other stimuli as well
  • Weber’s Law ([delta]I=KI) = K={delta}I/I

Question 15

What does Weber’s Law describe?

Answer 15

A statement of the relationship between the intensity of the standard stimulus and the size of the JND

Question 16

What is Fechner’s Law?

Answer 16

s= KIn(I/I0)

Question 17

What is Steven’s Power Law?

Answer 17

(s = cI)

- perceived stimulus intensity is related to the physical intensity of a stimulus by an exponential function

Question 18

What is the problem with threshold theory?

Answer 18

• it implies that thresholds (as a measurement) are absolute

- some stimulus presence occurs below threshold

Question 19

What is rate coding?

Answer 19

we infer the properties of the physical stimulus through the response rate (spikes per second) of neurons
- however, neurons are noisy (slight variations in the number of spikes released in response to a fixed sensory stimulus)

Question 20

What is signal detection theory?

Answer 20

a framework for measuring how people make perceptual decisions based on noisy perceptual evidence (ex. studying a mammogram to decide if there is a tumour or not - difficult to distinguish normal tissue from abnormal tissue)

Question 21

What is sensitivity?

Answer 21

the ease with which an observer can tell the difference between the presence and absence of a stimulus/the difference between two stimuli

Question 22

What is criterion?

Answer 22

An internal threshold that is set by the observer. If the internal response is above the criterion the observer will give one response (and opposite when below internal threshold)

Question 23

What does the criterion reflect?

Answer 23

A decision making bias in deciding if the signal was there or not

Question 24

How is sensitivity represented?

Answer 24

d’

Question 25

How can we measure sensitivity?

Answer 25

Take the difference of the mean of the curve showing the strength of perceptual evidence when no signal is present with the mean of the curve when a signal is present