week 1

Question 1

what is psychophysics

Answer 1

• Scientific discipline designed to determine a quantitative relationship
• between the physical characteristics of the stimulus and the sensory/perceptual responses of the observer
• signaled verbally or behaviorally

Question 2

What is the absolute threshold

Answer 2

The ultimate capability of the sensory system – minimum intensity that an observer can reliably detect

Question 3

What is the difference/discrimination threshold

Answer 3

Minimum amount by which a stimulus must be changed to produce a noticeable change in sensation

JND = just noticeable difference

Question 4

what are the

Factors that affect threshold

Answer 4

Random variations in physical stimulus
Physiological variations in the nervous system
Participant attention level
Psychological bias

Question 5

What are the 3 different psychophysical methods?

Answer 5

Method of limits
Method of adjustment
Method of constat stimuli

Question 6

What are the 3 ways of controlling guessing and bias?

Answer 6

Catch-trials
Forced-choice methods
Signal detection theory

Question 7

What is the method of limits

Answer 7

-Examiner begins with undetectable stimulus and gradually increases the intensity until the threshold is reached
-Can go in reverse order too
-Participant is passive in controlling stimulus

Question 8

What is the method of adjustment

Answer 8

• Observer begins with undetectable stimulus and gradually increases the intensity until the threshold is reached
• Can go in reverse order too
• Participant is active in controlling stimulus

Question 9

what are the disadvantages to

method of limits
method of adjustment

Answer 9

• Subjective to criterion and bias effects
• Subjects may also be prone to respond according to their expectation of which stimulus is likely to be presented
• If timing is uncontrolled and timing is a variable that affects threshold measure then it is a problem

Question 10

what is the method of Constant Stimuli

Answer 10

• Designed to overcome the expectation of the stimulus
• Time consuming and inefficient
• Most accurate
• Stimuli at all levels must be presented an equal number of times
• Order of stimulus presentation is random

Question 11

What are the two presentations of MCS

Answer 11

1. Single interval presentations
2. Multiple interval procedure – forced choice

Question 12

what is SIP

single interval presentations

Answer 12

• subjects say yes or no to if they see it on every trial
• Method is prone to criterion effects
• Response bias present
• Can introduce catch trials where no stimulus is presented – proportion of yes
• Reponses to these trials become guess rate

single interval presentations

Question 13

what is MIP

multiple interval procedure - forced choice

Answer 13

• Helps to remove criterion choice
• Participant is presented with 2 or more alternatives, and they must pick 1 even if they think they never saw the stimulus
• The question if not whether but which one

multiple interval procedure - forced choice

Question 14

What is the adaptive staircase method?

Answer 14

Selects subsequent stimulus levels based on the previous response history

Question 15

How to measure discrimination threshold

Answer 15

Ask observer to detect a change in characteristic of a stimulus
Threshold for detection of differences = jnd

Question 16

what is perception

Answer 16

translation of the physical world into a pattern of neural activity that can be used by the brain to guide behavior

Question 17

what is sensory overload

Answer 17

Perceptual system overcome potential overload by

Using codes of stimulus regularity and repetition
Becoming selectively tuned, through evolution to biologically relevant events **

Question 18

what is vision science the study of

Answer 18

complex interplay of mutually interdependent events

Vision Science is the study of all these events with regards to the sensory modality of vision

Question 19

what is radiometry

Answer 19

measurement of light energy in physical energy units using radiometric devices

Question 20

what is photometry

Answer 20

measurement and specification of light related to its effect on human vision

i.e., considering human sensitivity to different wavelengths

Question 21

what are the 3 different approaches to study

Answer 21

psychological approach
biological approach
theoretical approach

Question 22

what are the two psychological approaches

Answer 22

Phenomenological
Experimental/Psychophysical

Question 23

what are the two biological approaches

Answer 23

Neurophysiology – single cell recording; lesion studies; chemical/electrical stimulation

Electrophysiology and Brain Imaging Techniques

Question 24

what is the subsection for theoretical approaches

Answer 24

Systems and computational analysis

Question 25

# Psychological approach what is the phenomenological approach

Answer 25

Least formal approach Verbal reports and descriptions Unable to control variables Impossible in non-verbal perceivers

Question 26

# psychological approach what is the experimental approach

Answer 26

* Allows stimulus paraments to controlled and replicated * Experimental approach untangles the confounding variables that occur in natural situations

Question 27

# psychological approach what is psychophysics

Answer 27

* Non-invasive experimental technique that uses behavioral responses to assess how visual stimuli are being processed * Disadvantage is that it cannot provide info about specific underlying neural events

Question 28

# biological approach what are single cell techniques

Answer 28

* Records activity of a single neuron by placing electrode close to the cell whilst manipulating stimulus parameters * Determines the properties of individual cells but tells us little about how that cell contributes to overall perception

Question 29

# biological approach what is a lesion technique

Answer 29

Involves destroying part of the nervous system and observing behavioral consequences of lesion

Question 30

# biological approach what is electrophysiology and VEP

Answer 30

Relates perceptual response to changes in electrical activity evoked by stimulus EPs are recorded by placing electrodes on the scalp, i.e. non-invasive technique Difficult to pinpoint exact locus of activity and computationally laborious

Question 31

# biological approach whatis brain fuctional imaging and positron emission tomography

Answer 31

* Tracks increased metabolic demand, i.e. glucose and oxygen utilization that occurs with stimulation, using a radioactive tag chemical * Limited spatial resolution; health and safety guidelines limit exposure

Question 32

# biological approach what is brain functional imaging with functional magnetic resonance imaging

Answer 32

* Tracks increased metabolic demand by measuring changes in magnetic properties of blood that are oxygen level dependent * superior spatial resolution; inferior temporal resolution compared with MEG

Question 33

# biological approach brain imaging with Magnetoencephalography

Answer 33

Changes in magnetic fields produced by electrical activity of the brain are recorded using extremely sensitive magnetic detectors Superior temporal resolution; inferior spatial resolution

Question 34

# theoretical approach what is computational approach

Answer 34

* Understand vision by building compute models of the visual system * What is the program by which input, hardware and output are related * Success is judged by comparing program output against psychological and neurophysiological data