Introduction
Research Methods
Fall 2010
Tamás Bőhm
What is psychophysics?
• Subdiscipline of experimental psychology
• Measuring the relationship between physical
stimuli and their subjective correlates
(percepts)
• Physical dimensions: light intensity, sound
intensity, sound frequency etc.
• Subjective/perceptual dimensions: brightness,
loudness, pitch, etc.
• Psychophysics: usually refers to vision
• Psychoacoustics: hearing
Why do we need psychophysics?
• Physical dimensions ≠ perceptual dimensions
• Light intensity ≠ brightness
http://web.mit.edu/persci/people/adelson/
Why do we need psychophysics?
• Physical dimensions ≠ perceptual dimensions
– If you double the intensity of a tone, you won’t hear it
twice as loud! (only 60% louder)
– If you change the frequency of a tone, loudness will
also change (loudness depends both on intensity and
on frequency)
• Sound intensity ≠ loudness
Why do we need psychophysics?
• Physical dimensions ≠ perceptual dimensions
Some practical uses
• Absolute threshold of hearing
Some practical uses
• Aging and the absolute threshold of hearing
Wikipedia
Some practical uses
• Hearing aids:
compensating for
audibility loss by
measuring
individual
audibility curves
pure-tone audiometry
Fletcher, 1929
Some practical uses
• Mp3 music coding:
1:10 compression by
applying results from
psychoacoustics
– Absolute and
difference
thresholds
– Properties of
binaural hearing
(joint stereo)
– Masking effects
Some practical uses
• Military camouflage:
detectability of patterns
(different shapes and
colors) from different
viewing distances, under
different conditions