This is further borne out by his experience in his present position. Addressing a succession of new tasks, the interest of novelty has stimulated him to an uncommon degree and produced an unbroken record of high efficiency. That this has continued over a considerable period is partly due, beyond doubt, to the sustained interest in his work excited by the broadness of the field before him, the bigness of the company, the size of the appropriation at his disposal, the unusual experience of scoring hit after hit by comparison with the house's low standards, the frank and prompt appreciation of his superiors, and substantial advances in salary. It is only human to be more or less dependent upon novelty. If I am to stir myself to continuous and effective exertion, I must frequently stimulate my interest by proposing new problems and new aspects of my work. If I am to help others to increase their efficiency, I must devise new appeals to their interest and new stimulations to action. If I have been dependent upon competition as a stimulus <p 241> I must change the form of the contest--a fact which receives daily recognition and application by the most efficient sales organization in the country. If I have been depending upon the stimulating effect of wages, there is profit occasionally in varying the method of payment or in furnishing some new concrete measure of the value of the wage. To the average worker, for example, a check means much less than the same amount in gold. In deference to this common appreciation of ``cold cash,'' various firms have lately abandoned checks and pay in gold and banknotes, even though this change means many hours of extra work for the cashier. _At every stage of our learning, progress is aided by the utilization of old habits and old fragments of knowledge_. In learning to add, the schoolboy employs his previous knowledge of numbers. In learning to multiply he builds upon his acquaintance with addition and subtraction. In solving problems in percentage his success is measured by the freedom with which he can <p 242> use the four fundamental processes of addition, subtraction, Multiplication, and division. In computing bank discount, his skill is based on ability to employ his previous experience with percentage and the fundamental processes of arithmetic.