Signal Detection Theory

Psychophysik (1860) Stimulus Perception Neural activity Neurophysiology Inner psychophysics outer psychophysics

Measuring perceptual experience Detection Identification Discrimination scaling

Measuring threshold … Classical ways for perceiving a stimulus Method of adjustment Method of limits Method of constant stimuli

Psychometric function

Classical threshold T = a + (b-a). 50 – pa/(pb-pa)

Objections to classical threshold Smooth transition Subliminal perception Response bias

Signal detection theory Sensory process Vs Decision process

Response bias Liberal response strategy Conservative response strategy Internal criterion

Signal detection paradigm Signal trials Noise trials

Response bias toward ‘Yes’

Response bias toward ‘No’

d’= Z(hit rate) – Z(false alarm rate) d-prime! d’= Z(hit rate) – Z(false alarm rate)

ROC curve