in one line is correlated with that
same ability in others has not yet been ascertained. That there is some
correlation is probable, but at present the safest way is to think in
terms of special memories and special acquisitions. Some experimental
work has been done to discover the order in which special memories
develop in children. The results, however, are not in agreement and the
experiments themselves are unsatisfactory. That there is some more or
less definite order of development, paralleling to a certain extent the
growth of instincts, is probable, but nothing more definite is known
than observation teaches. For instance, every observer of children knows
that memory for objects develops before memory for words; that memory
for gestures preceded memory for words; that memory for oral language
preceded memory for written language; that memory for concrete objects
preceded memory for abstractions. Further knowledge of the development
of special memories should be accompanied by knowledge as to how far
this development is dependent on training and to what extent lack of
memory involves lack of understanding before it can be of much practical
value to the teacher.

Just as repetition or exercise tends to fix a fact in memory, so disuse
of a connection results in the fact fading from memory. "Forgetting" is
a matter of everyday experience for every one. The rate of forgetting
has been the subject of experimental work. Ebbinghaus's investigation is
the historical one. The results from this particular series of
experiments are as follows: During the first hour after study over half
of what was learned had been forgotten; at the end of the first day two
thirds, and at the end of a month about four fifths. These results have
been accepted as capable of rather general application until within the
last few years. Recent experiments in learning poetry, translation of
French into English, practice in addition and multiplication, learning
to toss balls and to typewrite, and others, make clear that there is no
general curve of forgetting. The rate of forgetting is more rapid soon
after the practice period than later, but the total amount forgotten and
the rate of deterioration depend upon the particular function tested. No
one function can serve as a sample for others. No one curve of
forgetting exists for different functions at the same stage of
advancement or for the same function at different stages of advancement
in the sam