The second major influence on research in mathematics.
education is psychology. One of the preconditions for the
development of mathematics education, according to Schubring
(l988b), was the age-graded school in which the teacher could
deal with a class as a group and begin to observe patterns of
cognitive development. Near the turn ofthe 20th century, psycho-
logical institutes in Germany and psychology departments in the
United States began to undertake empirietl studies in education
(Husén, 1983). Psychology became the “master science