The Greek philosopher Aristotle said that a persons highest happiness comes from the use of his or her intelligence. Religious books such as the Koran and Bible discuss faith as a form. of happiness. The British scientist Charles Darwin believed that all species were formed in a way so as to enjoy happiness. And, the United States declaration of independence guarantees 'life, liberty and the pursuit of happiness as a basic human right'. People throughout history may have had different ideas about happiness. But today, many people are still not very sure about it. Some findings are not surprising. For example, the database suggests that married people are happier than single people. People who like to be with other people are happier than unsocial people. People with children are equally happy as couples without children. And wealthier people are only a little happier than poorer people. This database also shows that studying happiness no longer involves just theories and ideas. Economists, psychiatrists, doctors and social scientists are finding ways of understanding happiness by examining real sets of information. Happiness is an extremely popular subject, if you search for 'happiness' on the web site of the online bookseller, Amazon. com, you will find more than two hundred thousand results. Dan Gilbert teaches psychology at Harvard University in Massachusetts. He recently looks at the way the human mind is different from other animals because we can think about the future and use our imaginations. He also explains how our minds can trick us in a way that creates difficulties in making happy choices for the future. 'Most of the time when people are wrong about how theyll feel about the future, theyre wrong in the direction of thinking that things will matter to them more than they really do. We are remarkable at our ability to adjust and a-dapt to almost any situation but we seem not to know this about ourselves. And so we mistakenly predict that good things will make us happy, really happy for a really long time. Bad things, why theyll just slay us. It turns out neither of these things is on the whole true. ' The first paragraph in the passage is mainly talking about______.