A new monthly magazine called Human Nature and dealing with the "Human Sciences" was announced yesterday by its publisher, Harcourt Brace Jovanovich Inc.

Human Nature will sell for $1.75 a copy on newsstands or $15 for a year's subscripton and its publicists say it is designed to bridge a gap "between popular journalism and the other."

William Jovanovich took a simpler view at the launching ceremonies yesterday, saying: "We don't know who wants to read this. We're going to find out."

Jovanovich, who has turned what was a small book publishing company into a conglomerate that now also controls insurance companies and performing dolphins, said he had not explored whether the world needs Human Nature, but he hopes a lot of people will want it.

"We're in this for the long haul," he said, adding that there was no expectation of immediate success. "We're not going to quit this unless it is generally a bore," Jovanovich said.

The chairman then drew laughter by telling assembled reporters that "I can't get The Saturday Evening Post out of my mind." He professed to have the world's greatest collection of written material on the death of The Saturday Evening Post and promised that should Human Nature, his first general circulation magazine, fail, he would call reporters together for an announcement similar to yesterday's rather than let it die a lingering death like The Saturday Evening Post's.

He ended his remarks at a champagne brunch at the 21 Club by telling his audience of reporters he dislikes such occasions and "I hope that you all get drunk this morning and write sort of silly articles."

I had two glasses of champagne and wrote this.

Robert Ornstein, an author and editor of several books on psychology who is director of Human Nature, and Elizabeth Hall, the new magazine's editor, told the brunch that there will be articles on sneezing, on blood, on prenatal care, on immunotherapy and cancer and what they hope will be the definitive article on the laugh.

Ornstein said the magazine would use "the best people in the world" in the human sciences but not only such "sanctified experts." He said there also would be room for novelists and philosophers.

Jovanovich made it clear he wasn't so enthusiastic about including the noscientists. "I don't think literature, history and philosophy have been a great deal of help recently. Maybe we can stick 'em," he said.

That ended the presentation. More Jovanovich champagne was poured and the food was served.