Psychophysics w4 Flashcards
What is psychophysics?
A branch of psychology aiming to study the relationship between the physical world and the mental world
What was Fechner’s contribution to psychophysics?
He wanted to write an equation for the physical intensity of a stimulus and the quantity of sensation
What is the absolute threshold?
The quantity of something before it is detected - smallest amount of light that can be detected in a dark night
What are absolute sensory values? What is this method known as?
Values established by increasing the units of intensity of stimulus and measuring %percentage% detections. AKA a method of constant stimuli, using a small no. of ppts.
What is the difference threshold?
How much something can be changed before the change is detected - 2 or 3 spoons of sugar in tea is too similar to tell difference. Rather than detection of a sensation, detection of a difference in sensation
What is the measure of difference threshold known as?
JND - just noticeable difference. A method of constant stimuli - pairs of stimuli are presented with one always same - ppt indicates if they are different. JND is taken at 75% of time, 50% would be chance performance.
What is the staircase method? 2 types of this?
Start with easily discriminated pairs, if discrim is made then reduce difference, if not then increase it. 3 right to get harder, 1 up if wrong.3 down 1 up or 2 down 1 up.
What did Weber say - Fechner law?
The required change of stimulus is proportional to the level of the stimuli - need higher units of stimuli to get same effect.
What is Steven’s Power Law?
Different psychophysical functions could be negatively accelerating or positively accelerating.
What is Signal Detection Theory?
Not all responses to a stimulus or absence of stimulus are correct. SDT tells us how easy stimuli are to discriminate.
What are the 4 possible outcomes of Signal Detection Theory?
Stimulus present + respond yes = hit.
Stimulus absent + respond Yes = false alarm.
Stimulus present + No = miss
Stimulus absent + No = correct rejection.
What does Signal Detection Theory tell you?
Proportions of hits + false alarms tells you discrimination (d) - how easy task was, low d = more overlapping. And criterion (b(beta)) the level the ppts used to make decision (conservative or liberal).
What can changes in performance be due to? Which is more interesting to look at?
- Result of change in sensitivity (ability to make a discrimination)
- Result of change in criterion (where one decides to have a cut off).Discrimination changes are more interesting usually.
Herman von Helmholtz passed neural impulses through frogs legs - what is this an example of?
An example of studying speed of responses - different mental processes require different lengths of time.
Can reaction time reveal mental processes?
Modelling of processes suggest that additive effect can be found in single stage processes.
