Elements of Psychophysics, Vol. I

Page
X. The Fact of the Threshold The "Schwelle" or threshold is the point at which a physical stimulus becomes strong enough to be perceived by the mind . . . . . . . . . . . . . . . . . . . . . . . . 238
1) Intensive Threshold Relates to the strength or magnitude of a sensation, such as brightness or volume . . . . . . . . . . . . . . . . . . . . . . . 240
a) Stimulus Threshold The minimum intensity required for a stimulus to be felt at all; also called the absolute threshold . . . . . . . . . . . . . . . . . . . . . . . 240
b) Difference Threshold The smallest change in stimulus intensity required to notice a difference . . . . . . . . . . . . . . . . . . . 242
2) Extensive Threshold Relates to the spatial or temporal span of a sensation, such as the smallest area felt on the skin . . . . . . . . . . . . . . . . . . . . . . 245
3) More general considerations regarding the threshold . . . . . . . . . . 246
4) Implications of the existence of the threshold . . . . . . . . . . . . . . 249
XI. Detailed information on the magnitude and dependency relationships of
threshold values in the various sensory domains . . . . . . . . . . . . . 254
1) Intensive threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
a) Light and color . . . . . . . . . . . . . . . . . . . . . . . . . . 255
b) Sound intensity and pitch . . . . . . . . . . . . . . . . . . . . . 257
c) Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
d) Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
2) Extensive threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
a) Sense of sight . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Specific determinations regarding the smallest recognizable sizes . . . 280
Specific determinations regarding the smallest recognizable distances . 288
α) Two distant points . . . . . . . . . . . . . . . . . . . . 288
β) Two distant threads . . . . . . . . . . . . . . . . . . . . 289
γ) Striped and checkered figures . . . . . . . . . . . . . . . 289
Behavior of the peripheral parts of the retina in recognizing
the smallest sizes and distances . . . . . . . . . . . . . . . . 293
Distance differences (Visual estimation original: "Augenmass," literally "eye-measure"; the ability to judge distances or sizes by sight alone) . . . . . . . . . . . . . . . . . . 294
b) Sense of touch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
c) Perception of time and motion . . . . . . . . . . . . . . . . . . . . 296
XII. Parallel law to Weber's Law Weber’s Law states that the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus . . . . . . . . . . . . . . . . . . . . . . 300
1) Weight experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
2) Experiences in the field of light sensation . . . . . . . . . . . . . . . 323
3) Experiments in the field of extensive sensation . . . . . . . . . . . . 329
XIII. Laws of mixing phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . 329