The judgment of very weak sensory stimuli : with special reference to the absolute threshold of sensation for common salt / by Warner Brown.

  • Brown, Warner, 1882-1956.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The judgment of very weak sensory stimuli : with special reference to the absolute threshold of sensation for common salt / by Warner Brown. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    29/76 (page 225)
    1914] Brown: The Judgment of Very Weak Sensory Stimuli 225 Table XI Observer Levy. 80 Rounds op Weak Solutions ‘ ‘ strong ’ ’ = stronger than the one in question “ + ” = positive judgment of salt + jdmt. preceded by: — jdmt. preceded by: Sol. in % NaCl f weak 4- strong weak strong Ojdmt. -f 0 sol. weak 1 strong weak strong 0 i^t. 0 sol. 0.0% 0 15 0 20 0 0 19 0 21 5 0.025 2 9 0 9 3 3 31 2 19 2 0.05 1 5 5 11 2 1 24 6 22 3 0.075 3 5 1 19 3 6 19 8 14 2 0.1 4 4 3 6 1 5 17 15 20 5 0.125 3 14 14 12 2 4 15 6 7 3 0.15 6 9 7 12 2 5 15 11 10 3 0.175 6 10 9 18 4 4 9 10 8 2 0.2 6 6 17 6 1 13 10 9 8 4 0.225 13 7 10 9 2 10 3 12 10 4 0.25 7 5 14 7 2 12 9 19 1 4 0.275 10 5 13 3 1 14 5 19 6 4 0.3 15 5 24 2 1 9 3 15 2 4 0.325 17 3 22 3 2 8 1 21 0 3 0.35 10 0 32 0 1 14 0 18 0 5 Total 103 102 171 137 27 108 180 171 148 53 Observer Kohlberg (Table XIII) shows a contrast effect between the stimuli, like that of the others; that is, the prob- ability of a positive judgment is increased if the stimulus just ‘ preceding was weaker than the one in question. But there is l also another tendency at work, for the contrast effect is not equally marked in aU cases. When there is contrast between •; two solutions, A and B, the observer is apt to attest the contrast by calling B salt if it is really salter than A, or vice versa, and j this tendency exists without regard to the judgment passed upon f A; but the striking fact appears that this tendency is stronger if the judgment of A was mistaken. Normally 54 per cent of the judgments in this series are positive, but after weaker solu- tions 85 per cent of them are positive; after weaker solutions which have been called “salt” 94 per cent of the judgments are positive (“salt”), while if the weaker preceding solution was