"The human being is the only animal that thinks about the future. Now ... I do recognize that non-human animals often act as though they have the capacity to think about the future. ... For example ... the squirrels in my yard act as though they know they will be unable to eat later unless they bury some food now ... [but instead] they have regular squirrel brains that run food-burying programs when the amount of sunlight that enters their regular squirrel eyes decreases by a critical amount. Shortened days trigger burying behavior with no intervening contemplation of tomorrow ... Until a chimp weeps at the thought of growing old alone, or turns down a Fudgesicle because it already looks to fat in shorts, I will stand by my [statement]. We think about the future in a way that no other animal can, does, or ever has, and this simple, ubiquitous, ordinary act is a defining feature of our humanity. ...

"The greatest achievements of the human brain is its ability to imagine objects and episodes that do not exist in the realm of the real, and it is this ability that allows us to think about the future. As one philosopher noted, the human brain is an 'anticipation machine,' and 'making future' is the most important thing it does."

Daniel Gilbert, Stumbling on Happiness, Knopf, 2006,