There is never enough time or money; this much we all know. Yet a new study finds that when people estimate how much of each they will have in the future, they are consistently more likely to overestimate their time than their dollars. Dr. Gal Zauberman of the University of North Carolina and Dr. John Lynch of Duke, professors of marketing, have found that future expenditures of time are always psychologically discounted - that is, a future disbursement of time seems to be worth less than an outlay of time in the present.

This makes it easier for people to volunteer for time-consuming tasks if they are told they do not have to do it right away. Even though they know, rationally, that an hour today is just as long as an hour a month from today, and even though there is no reason to believe that they will have any more spare time next month, time discounting makes taking on the new task easier.

And when, as inevitably happens, that future day turns out to be just as busy as today, people seem to learn little from the experience. The study, published this month in The Journal of Experimental Psychology: General, included seven experiments in which people invariably predicted that they would have more spare time on the same day next week, or next month, than they had on that day.

In one survey, the researchers asked undergraduates at the University of North Carolina to imagine two situations. In the first, the students were told, "Think about your activities today and your available spare time for the same day of the week a month from now. On which day do you expect to have more spare time?" In the second, the students were told: "Think about your expenses today and your available spare money. Now consider your likely expenses and available spare money for the same day of the week a month from now. On which day do you expect to have more financial reserves?"

Although the students believed they would have more of both in the future, they were much more strongly convinced that they would have more time than they were of having more money. In six similar experiments, these conclusions were reinforced. Dr. Zauberman observed, "Our perception of the context in which events occur is different for the future than for the present, and this difference is much sharper for time than for money."

The authors speculate that it is easier to estimate future money because a dollar today is the same, conceptually, as a dollar three months from now. Moreover, people realize that money can be saved, or that an expense can be put on a credit card. Because there are no bank accounts or credit cards for time, spending it is psychologically a very different proposition. People concentrate on different aspects of a task when it is far away in time, Dr. Lynch said. "When we think about a task in the distant future," he said, "we focus on the benefits - the good stuff. When we think about doing a task today, we think about the mundane and less interesting details."

This psychological quirk seems to guarantee that people will always be pressed for time, willing to take on tasks not because they regard them as valuable, but just because the promised execution is far enough in the future. "The danger," Dr. Zauberman said, "is that this tendency can lead us to volunteer for trivial tasks, and then not have time to do the things that are really important to us."

Dr. Lynch offered a more optimistic interpretation. "There is some debate about it, but this may have an adaptive value," he said, adding that the discounted perception of future time may allow people to schedule, and therefore eventually accomplish, what they really hold dear.