Psychophysical Methods Flashcards
what is the independent variable in psychophysics
controlling/changing the physical stimuli
best to change randomly
what is the dependent variable in psychophysics
measuring the perceptual/behavioral response
the minimum value of a stimulus required to elicit a perceptual response or an altered perceptual response
threshold
the lowest level of a stimulus for which a response is elicited (under ideal conditions)
absolute threshold
the minimum difference in stimulus levels between two stimuli that can be detected
difference/ increment threshold
the description of the stimulus in terms of luminance and spatial (or temporal) extent is called
luminance profile
luminance profile x-axis
spatial extent
-in visual angle (degree) or linear angle (mm)
luminance profile y-axis
luminance
-in cd/m^2
(-) target / (+) polarity are when
target is darker than the background (like standard VA chart)
original threshold theory / Fechner stated that
- threshold is all or non
- static (single) threshold
classical theory of threshold stated that
- threshold is a sigmoid (S-shaped) curve
- threshold varies
modern theory of threshold states that
- there is no threshold
- signal detection theory
4 reasons why threshold varies
- stimulus
- neural activity
- attention
- psychological bias
typically, the best most accurate method
method of constant stimuli
what is the only method that gives the sigmoid (S-shape)?
method of constant stimuli
pros and cons of method of constant stimuli
pros: very accurate, addresses attention issue of variability
cons: very slow and inefficient, does not get rid of bias
presenting each stimulus level in increasing or decreases order is called
method of limits
disadvantages of method of limits
patient bias/attention
- bases current judgement on previous responses
- anticipates transition point
descending limits: we think it is ___ than it actually is
lower
ascending limits: we think its ___ than it actually is
higher
simplest method but usually the worst
method of adjustment
2nd fastest method
staircase
best method in the table is
staircase
what method requires a lot of computation
signal detection theory
what has magnitude but no obvious scale or units
sensations
how can you measure sensations?
- ratio scaling (ratio production or ratio estimation)
- magnitude scaling (magnitude production or magnitude estimation)
