[7] In the tables of the third and fourth groups, there is a markeddivergence between the a priori and a posteriori probable error, for theaverage number of errors in 50, making the observed probable error toosmall. This can only be partly accounted for by the fact that thesubject formed the unconscious habit of retaining the number of eachkind of experiment in a set and answering according to that knowledge.In point of fact the plus errors and minus errors separately do notexhibit the singular uniformity of their sums, for which we are quiteunable to account. Thus in the fourth group we have:[8] The conclusions of this paper are strengthened by the results of a series of experiments on the color sense, made with the use of a photometer by Mr. Jastrow. The object was to determine the number of errors of a given magnitude, and compare the numbers thus ascertained with the theoretical numbers given by the probability curve. A thousand experiments were made. Dividing the magnitude of the errors from 0 to the largest error, made into 5 parts, the number of errors, as observed and calculated, that occur in each part are as follows: These numbers would be in closer accordance if the probable error were the same throughout, as it is not owing to the effects of practice, etc. Moreover, the experiments were made on different colors -- 300 on white and 100 each on yellow, blue, dove, pink, green, orange, and brown. These experiments were not continuous.
Charles Peirce and Joseph Jastrow article "On Small Differences in Sensation" relates to the history of psychology but experimenting on sensation, perception, and errors of differences. Peoples perception and sensation of things will vary but the error between them may be slight or large. Reading throughout the article and seeing the results of these experiments from my take differences start off larger and become minimal at the end. Giving results in a mathmatical form errors will start off larger and then as the observers run the experiment over and over participants differences grow closer. I believe this is due to experience and familiarization. Subconsciousness also plays a part too. When we feel comfortable with something we will use our knowledge or experience with something to gain an advantage. In someones head they may adjust and mentally prepare for what will come so this will vary the results of sensations. In regards of the history of psychology we talk about sensation and perceptions for people and as we can see it can vary but familiarization and experience plays a big part into those results.