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

Warner Brown

Date:: 1914

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.

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$what irregularly from daj' to day, but in general she gave fewer pasitive answers as the work progressed from week to week. ]\Iiss von der Xieuburg gave many more positive judgments in the preliminary experiments with the weak series of solutions than she did later on. The table shows, in the column for weak stimuli, that, after the third day, there was no further regular shift in the attitude of this observer. The attitude finally assumed required about one positive judgment to four negative judgments. There was a larger proportion of positive judgments on some days and a smaller proportion on others, but there was no further systematic change during the course of the experiment. When obsei’ver von der Nienburg came to take up the series of stronger solutions, her attitude underwent a change in this, as in other respects. In this series she gave, on the average, more than four positive judgments to one negative judgment, and there was a tendency to increase the proportion of positive judg- ments after the first day. From the data it is clear that this observer required two or three sittings before becoming adjusted to the conditions of the experiment, or before becoming adjusted to changed conditions, but that when once she had assumed an attitude toward either series she showed no disposition to disturb the normal ratio between the numbers of positive and negative judgments. These shifts in the general proportion of positive and negative judgments are significant because they involve a corresponding shift in the apparent pasition of the threshold. WTien there is a larger total number of positive judgments in the series, there will be more of them on each member of the series, and the result will be that a solution will appear to be above the threshold, whereas the same solution wmdd appear to be below the threshold if the total number of positive judgments in the series, and con- sequently on that solution, were reduced.$