In the present experiment the problems, methods adopted, and so on are the same as in the previous experiment (III). Its aim is to clarify the degree of constancy of form-color responses of the same subjects that were examined with the same method in the previous experiment about one year ago. The results are as follows : 1) The response-patterns obtained with controlled instruction as well as with experimental instruction in the experiment at an interval of about one year from the previous experiment have shown a tendency sufficiently convincing to sustain the results of the latter. In other words, with controlled instruction, in all ages older than 4, the form response is more dominant than the color response, and statistically there is a variation of the responses about the age of 7, thus supporting the tendency noted in the previous experiment. With the experimental instruction, on the other hand, it has been observed that there is a great variation in responses between the previous experiment and the present one. 2) As for the result obtained from the controlled instruction, the ratio of response constancy is 60% after the ages 6~7, and at the age of 11 it approaches 90%. The percentage of form response at age 12 in the previous experiment having been 100%, the ratio of constancy in this experiment has been 100% as expected. However, in the case of the experimental instruction, the constancy of response has proved low and varying. 3) It has been inferred that the response constancy as observed in "Lotto-Methode" depends not so much upon the conditions of response persistency in terms of an individual characterological "Eigentatigkeit" as upon those of constant responses to form-abstraction which accompanies the growth and development of the subjects. 4) It has been inferred that when we consider this "Form-Farbe" problem from the angle of the developmental tendency of abstraction ability, the traditional use of instruction according to the Lotto-Methode would methodologically be more valid and convincing. 5) Since in the experimental instruction method some factors are observed that have to do with the individual "Eigentatigkeit" presupposing some characterological conditions, the problem in the future would be to consider it from such an angle.