Guarantee is another thing that influences human psychology. One concern made a fortune by offering a dealers signed warrant. The dealer to whom one paid his money agreed in writing to pay it back if asked.

Being specific PLATITUDES and generalities roll off the human understanding like water from a duck. They leave no impression whatever. To say, "Best in the world," "Lowest price in existence," etc., is at best simply claiming the expected. But superlatives of that sort are usually damaging. They suggest looseness of expression, a tendency to exaggerate a careless truth. They lead readers to discount all the statements that you make.

An advertiser suffered much from substitution. He said, "Look out for substitutes," "Be sure you get this brand," etc., with no effect. Those were selfish appeals. Then he said, "Try our rivals' too"-in his headlines. He invited comparisons and showed that he did not fear them. That corrected the situation. Buyers were careful to get the brand so conspicuously superior that its maker could court a trial of the rest.

an offer limited to a certain class of people is far more effective than a general offer. For instance, an offer limited to veterans of the war. Or to members of a lodge or sect. Or to executives. Those who are entitled to any seeming advantage will go a long way not to lose that advantage.

An advertiser offered a set of books to businessmen. The advertising was unprofitable, so he consulted another expert. The ads were impressive. The offer seemed attractive. "But," said the second man, "let us add one little touch which I have found effective. Let us offer to put the buyers name in gilt lettering on each book." That was done, and with scarcely another change in the ads they sold some hundreds of thousands of books. Through some peculiar kink in human psychology the names in gilt gave much added value to the books.