A rational consumer is one who spends his income to maximize satisfaction. This means that the consumer will make choices that will provide the greatest level of satisfaction, given their limited income and the prices of goods and services. A rational consumer will consider the marginal utility (the additional satisfaction gained from consuming an extra unit) and the price of each good or service before making a purchasing decision. In contrast to what some people believe, being a rational consumer does not mean that a person behaves in a particular way all the time, or that they know the price of all goods and buy the cheapest, or that they are not influenced by advertisement.