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Chapter 1

Chapter 1

Course Code
Matthias Niemeier

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Psychophysical Methods:
-Method of Constant Stimuli:
- creating many stimuli w/ diff intensities to find the tiniest one that can be detected
- often 50% detection is designated as the threshold
- turns out that no such hard boundary exists
- b/c of variability in the nervous system -> stimuli near threshold may be detected and missed
- somewhat inefficient b/c much of subject’s time spent w. stimuli that are well above/below
-Method of Limits
- experimenter begins w/ same set of stimuli - i.e, tones that vary in intensity
- tones presented in order of increasing or decreasing intensity
-ascending order(faintest->loudest): asked to first report when they hear a tone
-descending order(loudest->faintest): report when tone is not longer audible
-results: some overshoot in judgments
-ascending: usually takes more intensity to report hearing a tone
-descending: takes more decreases in intensity to report the tone cannot be heard
- take avg of cross over points to be the threshold
-Method of Adjustment
- subject controls the change in stimulus
- may be the easiest method to understand b/c it’s similar to daily activities
- not usually used to measure thresholds
Signal Detection Theory
- quantifies the response of an observer to the presentation of a signal in the presence of a noise
- a straightfwd way to address how strong a sensation is would be simply to ask the subjects how
they rate it
-Magnitude Estimation: might ask listeners to assign #s of their choice to each sound
-Cross-Modality Matching: subject adjusts a stimulus of one sort to match the perceived
magnitude of a stimulus of a completely different sort
- for example: adjust brightness of light to match the loudness of a tone
- produces similar results across subjects
-S.S Stevens
- invented magnitude estimation
-Found Cases Where Frechner’s Law Would Not Work:
The Biology of Perception
- studies of animals tell us something about human senses
- assumption requires belief that there’s some continuity b/w the way animals and humans work
- encouraged study of animals
- claimed animals were in most ways very similar to humans
- study of animals was a good way to learn of the material parts of humans
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