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Vision science > week 1 > Flashcards

week 1 Flashcards

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1
Q

what is psychophysics

A
  • 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
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2
Q

What is the absolute threshold

A

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

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3
Q

What is the difference/discrimination threshold

A

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

JND = just noticeable difference

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4
Q

what are the

Factors that affect threshold

A

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

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5
Q

What are the 3 different psychophysical methods?

A

Method of limits
Method of adjustment
Method of constat stimuli

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6
Q

What are the 3 ways of controlling guessing and bias?

A

Catch-trials
Forced-choice methods
Signal detection theory

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7
Q

What is the method of limits

A

-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

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8
Q

What is the method of adjustment

A
  • 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
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9
Q

what are the disadvantages to

method of limits
method of adjustment

A
  • 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
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10
Q

what is the method of Constant Stimuli

A
  • 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
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11
Q

What are the two presentations of MCS

A
  1. Single interval presentations
  2. Multiple interval procedure – forced choice
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12
Q

what is SIP

single interval presentations

A
  • 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

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13
Q

what is MIP

multiple interval procedure - forced choice

A
  • 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

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14
Q

What is the adaptive staircase method?

A

Selects subsequent stimulus levels based on the previous response history

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15
Q

How to measure discrimination threshold

A

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

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16
Q

what is perception

A

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

17
Q

what is sensory overload

A

Perceptual system overcome potential overload by

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

18
Q

what is vision science the study of

A

complex interplay of mutually interdependent events

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

19
Q

what is radiometry

A

measurement of light energy in physical energy units using radiometric devices

20
Q

what is photometry

A

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

i.e., considering human sensitivity to different wavelengths

21
Q

what are the 3 different approaches to study

A

psychological approach
biological approach
theoretical approach

22
Q

what are the two psychological approaches

A

Phenomenological
Experimental/Psychophysical

23
Q

what are the two biological approaches

A

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

Electrophysiology and Brain Imaging Techniques

24
Q

what is the subsection for theoretical approaches

A

Systems and computational analysis

25
Q

Psychological approach

what is the phenomenological approach

A

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

26
Q

psychological approach

what is the experimental approach

A
  • Allows stimulus paraments to controlled and replicated
  • Experimental approach untangles the confounding variables that occur in natural situations
27
Q

psychological approach

what is psychophysics

A
  • 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
28
Q

biological approach

what are single cell techniques

A
  • 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
29
Q

biological approach

what is a lesion technique

A

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

30
Q

biological approach

what is electrophysiology and VEP

A

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

31
Q

biological approach

whatis brain fuctional imaging and positron emission tomography

A
  • 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
32
Q

biological approach

what is brain functional imaging with functional magnetic resonance imaging

A
  • 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
33
Q

biological approach

brain imaging with Magnetoencephalography

A

Changes in magnetic fields produced by electrical activity of the brain are recorded using extremely sensitive magnetic detectors

Superior temporal resolution; inferior spatial resolution

34
Q

theoretical approach

what is computational approach

A
  • 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

Vision science (6 decks)

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