The atmosphere of Madison, Wis. is brightened not only by the glimmer of sunlight off the lakes that crowd its office buildings, but also by the high percentage of well-educated, forward-thinking young professionals who settle there after graduating from the state's mammoth university at the other end of the main street. It is a good climate for breakthroughs.

Still, Rex Peterson, 31, a parole officer, gets the same reaction one might expect anywhere else, when he de-Peterson is taking turns with another person working six months at the parole office and then taking six months off.

"I the barber shop, for instance, where it's natural for one man to ask another what do you do? When I tell them, they're likely to say, 'Well, you don't have a real job,' or 'you're just lazy."

Peterson doesn't have what some would consider a solid reason for wanting the extra time off, such as children at home, or an illness, or some specific creative urge. "I wanted some time for introspection," he said, "to think where I'm going and what I want to do, to read, to travel . . . to realize some dreams."

He doesn't miss the other half of his $16,000 annual salary much. He and his wife, a teacher, had agreed that some things are simply more important than money. "Our only sacrifice has been in no longer accelerating our standard of living . . . It's easy to make just enough to live.

"I suppose I haven't achieved the American dream of upward mobility," said Peterson, a trim, bookish-looking fellow with glasses and short hair. He and his wife decided to put off having children for a while, and they have invested some of their income in a 50-year-old house in which they are doing their own remodeling.

Social services "is a very emotionally draining job," Peterson said. "I'm a compulsive worker, so it takes me a lot of time to turn myself off . . . Geez, I found out it took me four months just to wind down."

His wife's teaching year ended at the beginning of the summer, about the same time Peterson's six-month "weekend" began. The two of them traveled for a while around Canada, camping out. (Fortunately), he noted, the woman who is sharing the other half of his job prefers the winter months off). Peterson devoted other side interests and "to thinking about my life."

"There is a distinction between free time and leisure time," he said. "The latter is open ended.I think it is one of the biggest challenges in life. Few people know how to handle it. I've been trying to learn."

As his time off drew to an end, he said, he started looking forward to going back to work, to seeing the people he works with.

For years, off drew ot an end, hwithout success, Peterson had been asking his bosses to give him a half-year work schedule. He finally got his wish when the state started a federally funded experimental program designed to split jobs up in unsual ways.

In his line of work, over a period of time, Peterson said, "a person gets to where he doesn't have much left to give. He becomes cynical . . . But if you've taken a half-time job over a full-time job, you've made a choice. You obviously expect the job to be more meaningful than just a check. So I figure, you're a pretty worthwhile employee, dollar for dollar . . ."

Of course, in a job where you aren't turning out something like widgests, he noted, "that's pretty difficult to measure, or prove."