Child psychology Vol-3 by Vilhelm Rasmussen

When in constant intercourse with children in their everyday life we are in a position to obtain a far better insight into their thought-processes and their general psychological condition than can be arrived at by means of tests; for both when the child is occupied playing with its toys and in general conversation we very often find remarkable instances of thought-activity, extending even to the criticism of others. In Child Psychology, I. p. 117 ff., I have quoted a number of examples of early criticism and doubt; and being as I am of the opinion that the critical sense is of extremely high value, and should therefore be carefully cultivated in education, I have been particularly on the alert to remark any evidence of the same in the case of R. or S.

When R. was four years and three months old she saw four portraits in a book and said: “There are three.” I corrected her, saying: “No, there are four;” whereupon R. continued: “But when one was gone there were three.” She could in other words subtract one from four.