ABSTRACT
This chapter includes two setups that allow horizontal and vertical lines to trace, the problems are: to establish how the subject comes to compose them to obtain oblique lines in different directions and to analyze the subject's comparisons between the two situations. It includes some stages: stage I; Level IIA and Levels MB and III. In level IIA 7 to 8 years of age there is a second level at which the subject discovers on his own how to compose verticals and horizontals into diagonals. The sequence of four developmental levels is an elegant example of superimposed operatory acquisitions. At Stage I, the subject gets the skills. Level IIA discovers the possible coordination of these two operators V and H; without this, the subject could not move beyond the two initial directions. At Level IIB the subject finds the way to vary V and H in a positive or negative direction, without which all diagonals would have the same inclination.
