T1: Measuring experiences Flashcards
Sensation
1) bottom-up process
2) ability to detect stimulus.
Perception
1) top-down process
2) giving meaning to a detected sensation.
The Steps of the Perceptual Process
a) Stimuli:
Step 1 - environmental stimulus
S2 - reflection and transformation of light
b) Receptor processes:
S3 - Transduction
c) Neural processes:
S4 - Neural processing (network from the visual receptors -> retina -> back of the eye -> primary receiving area = cerebral cortex)
d) Behavioural responses:
S5 - Perception = awareness
S6- Recognition = meaning/category
S7 - Action = motor activity.
Transduction
transforming light energy into electrical energy.
Bottom-up processing
- data based
- stimuli based
Top-down processing
- knowledge
- labelling
- often unaware
- more complex stimuli => TDP increases
Approaches for study of perception
Psychophysics
Physiological approach /. Electrophysiology
Neuropsychology
Cognitive neuroscience
Psychophysics
- Fechner’s methods of measuring perception
- relationship between stimuli and behavioural response
- Oblique effect (Coppola/Furmanski) = better vision for verticals or horizontals
Electrophysiology
present a stimuli and measure brain activity
Physiological approach
Relationship 1 = stimuli and physiological responses
R 2 = physiological resp. and behavioural resp.
Neuropsychology
- brain process => perception
- affects of brain damage on behaviour
Cognitive neuroscience
stimulus => brain process => perception (fMRI)
Methods of measuring perception
- Measuring thresholds with psychophysical methods
- Estimating magnitude
Absolute threshold
- minimum amount of stimulation necessary for a person to detect stimulus 50% of the time
- no distinct transition
Difference threshold or JDI
- minimum difference/change that exists between two stimuli
A higher sensitivity results in a
lower threshold
What are Fechner’s methods of measuring perception with psychophysical methods?
a) Method of Limits
- experimenter increases/decreases stimulus intensity
- threshold = average of all crossover points (change from Yes to No)
b) Method of Adjustment
- participants increases/decreases intensity
- accurate and fast
- threshold = barely audible
c) Method of constant stimuli
- random order
- different intensities
- yes/no or same/different tally
- threshold = detection 50% of trials
What are the two methods that together - constitute the Golden Standard for measuring perception with psychophysical methods?
a) Forced Choice Method
- verbal reports
- present two stimuli and choose the greater one
- absolute threshold = 75% correct interval chosen
b) Adaptive Testing/Staircase Method
- present whole stimuli range
- when stimuli is near threshold -> ascending until detection, then shift descending until no detection = reversal
- threshold = concentration when reversal occurs
How does estimating magnitude work?
- psychophysical method developed by Stevens
- participant assigned values to perceived magnitudes of the stimuli
- direct scaling : relationship between perceived magnitudes and stimuli
- explains response compression and expansion
Response compression
- intensity becomes greater than magnitude
=> lower ability to detect difference
Response expansion
- as intensity is increased, perceptual magnitude increases even more
=> greater ability to detect difference
Weber’s Law
- Stimulus = JND/ constant K
- sensation is a constant ratio
- liniar relationship
Fechner’s Law
- magnitude of sensation increases proportionally to logarithm of intensity
- not liniar
- describes only response compression
- indirect scaling => discrimination ability
- states that all JNDs are equal (incorrect)
Steven’s Power Law
- magnitude of sensation is proportional to stimulus magnitude raised to an exponent (power n)
- n < 1 = response compression
- n > 1 = response expansion
