61) {{U}}Man's preoccupation with time derives ultimately from his unique relationship to it. All animals are changed by it. But only human can manipulate it. {{/U}}
Like Proust, the French author whose experiences became his literary capital, man can remember the past. He can also summon up things to come, displaying imagination and foresight along with his memory. 62) {{U}}It can be argued that memory and foresightedness are the essence of intelligence; that man's ability to manipulate time, to employ both past and future as guides to present actions, is what makes him human. {{/U}}
To be sure, many animals can react to time after a fashion. A rat can learn to press a lever that will, after delay of some 25 seconds, reward it with a bit of food. 63) {{U}}But if the delay stretches beyond 30 seconds, the animal is at a loss. It can no longer associate reward so far in the future with present action. {{/U}}
Monkeys, more intelligent than rats, are better able to deal with time. If one of them is allowed to see food being hidden under one of two cups, it can choose the right cup even after 90 seconds has passed. 64) {{U}}But after that time interval, the monkey's hunt for the food is no better than chances predicts. {{/U}}
With the apes, man's nearest cousins, "time sense" takes a bit step forward. Even under the laboratory conditions, quite different from those they encounter in the wild, apes sometimes show excellent abilities to manipulate the present to obtian a future goal. Let's take a chimpanzees(黑猩猩) for example. 65) {{U}}They can learn to stack four boxes, one atop the other, as a platform from which it can reach a hanging banana. They also carry their ability to cope with the present action by means of tools like human being. {{/U}}And it is by the making of tools -- physical tools as crude as a stone chopper, mental tools are subtle as a mathematical question -- that man characteristically prepares for future contingencies.
Chimpanzees in the wild have been seen to strip a twig of its leaves to make a probe for extracting termites from their holes. Significantly, however, the ape does not make this tool before setting out on a termite hunt, but only when it actually sees the insects or their nest. Here, as with the banana and the crates, the ape can only deal with a future that is immediate and visible -- and thus halfway into the present.