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The psychologists speculated that, for at least two reasons, a bystander to an emergency would be unlikely to help when there were a number of other bystanders present. The first reason is fairly straightforward. With several potential helpers around, the personal responsibility of each individual is reduced: "Perhaps someone else will give or call for aid, perhaps someone else already has." So with everyone thinking that someone else will help or has helped, no one does.

As a marketing technique, the free sample has a long and effective history. In most instances, a small amount of the relevant product is provided to potential customers for the stated purpose of allowing them to try it to see if they like it.

It is much more profitable for salespeople to present the expensive item first, not only because to fail to do so will lose the influence of the contrast principle; to fail to do so will also cause the principle to work actively against them.