Psychophysics

Psychophysics

study of relationship between physical stimuli and sensation and perception they envoke

Psychophysics purpose

understanding these relationships help us quantify and predict how humans perceive sensory information

Weber’s Law

JND between 2 stimuli is proportional to magnitude of stimuli

Fechner’s Law

logarithmic relationship between physical magnitude of a stimulus and its perceived intensity

Steven’s Power Law

nonlinear relationship between stimulus intensity and perceived sensation across different sensory modalities

Signal Detection Theory

framework for understanding how people make decisions about perceiving signals amid noise

Signal Present

Is Target There?

Yes: Hit

No: False Alarm

Signal Absent

Is Target There?

Yes: Miss

No: Correct Rejection

Signal Noise Distribution

basic theory is that strength of signal and noise are represented by distributions

D

measures discriminability - noise curve and signal

C

criterion - response bias

Absolute Threshold

minimum amount of stimulus e required for a person to detect presence of a stimulus, 50% of time

Difference Threshold

JND - smallest detectable difference between 2 stimuli

Relative Threshold

deviations from baseline KND

Method of limits

experimenter changes the stimulus intensity in small steps → participate indicates when they detect stimulus

Method of Constant Stimuli

Multiple stimuli of varying intensities present → participant indicates which ones they detect

Method of Adjustment

the participant adjusts the stimulus intensity until they can detect it