Lecture 4 - How do we measure abs threshold? Flashcards
How do we measure absolute threshold?
method of limits, method of adjustment, method of stimuli
Method of limits
what is the min amount of stimulus necessary to make that detection?
stimuli are presented at different intensities in ascending and descending order
order switches on each trial
do you hear that? see that? smell that?
crossover point
takes time: not very efficient
crossover point
when you’re crossing your own threshhold by changing your answer
the mean value of all the crossover points is that observer’s absolute threshold
method of adjustment
for each observer they turn up the stimulus intensity themselves until they detect it
quick test to see what your perceived threshold is
very fast method!
Method of constant stimuli
present a number of stimuli (6) with different intensities
really careful: the most accurate method
each of these stimuli is presented several times, but the order is random
you may have a large number of total stimulus presentations
the threshold is defined as the intensity at which the stimulus was detected 50% of the time
method of constant stimuli is the …. but it is also …..
most accurate, time consuming
method of adjustment is …. but not always
fast, as accurate
Subjects have different thresholds, so you need to use…
… a broad range of stimuli
we are most interested in the stimuli nearest…
….the crossover points for each subject
Adaptive staircase method
stimuli presented in a dynamic fashion to best fit the current test subject
stimuli adjust themselves during the course of the experiment
at the end of the experiment my set of stimuli would be different than yours
stimuli converge at “your” crossover points
look at and adapts to reversals (changes) in your responses and take an average
