The parents of the first child born by artificial insemination through the "Nobel sperm bank" lost custody of two other children after abusing them--apparently to make them smart--according to allegations in official records and statements from the children.

The parents won international attention after the birth in April of Victoria, fathered anonymously by a contributor to the sperm bank in Del Mar, Calif. The sperm bank collects sperm from Nobel Prize winners and other "creative, intelligent people" to inseminate women who volunteer in the hope of producing geniuses.

The two children said yesterday their natural mother and stepfather, John T. (Jack) and Joyce Kowalski, gave them massive amounts of extra schoolwork to do at home, and their stepfather whipped them with straps when they made mistakes. The Kowalskis also served prison sentences three years ago for fraud.

"They said they were sorry," Mrs. Kowalski's son recalled. "They said they were trying to help us. They wanted us to do work and be smart."

Joyce Kowalski is the former Joyce Naunapper, who with her husband Eric Naunapper raised the two children in Des Plaines, Ill. When the Naunappers separated in 1974, the children stayed with their mother, who soon married Jack Kowalski.

Two years later, the natural father petitioned for custody, charging child abuse. An investigator for the Illinois Department of Children and Family Services recommended the children to be given to the father, according to an account of the Kowalskis' background published yesterday in the Chicago Tribune. The children now live with Eric Naunapper in Des Plaines.

The Kowalskis later moved to Arizona, where they served a sentence in federal prison from 1978 to 1979 for mail fraud and filing false applications for loans.

The Kowalskis told the story of Victoria's birth by artificial insemination to the National Enquirer, which published a feature in its June 29 edition.

"We'll begin training Victoria on computers when she's 3, and we'll teach her words and numbers before she can walk," Jack Kowalski told the Enquirer.

Many geneticists are skeptical that the sperm bank scheme will produce particularly brilliant offspring.

A spokesman for the sperm bank said, "It isn't that we don't screen the applicants, it's just that we have to go on what they tell us . . . . With the attention of the world focused on this child, we don't expect any problems to arise."

Telephone calls to the Kowalski residence in Phoenix went unanswered yesterday, and Mrs. Kowalski's former husband did not want to speak with reporters.

Mrs. Kowalski's children, Donna Naunapper, now 15, and Eric Naunapper Jr., now 16, recalled the beatings yesterday in telephone interviews.

"The whippings were based on work," Donna said. "Like sometimes we didn't get things right and we were whipped. But there was love. It wasn't as if they kept us in a closet and took us out to whip us. They loved us, and they hugged us."

She said she and her brother had, on average, been whipped "pretty hard" several times each week with a belt or leather strap.

"She didn't want to hurt us," Donna said. "But I guess she loved Jack so much she went along with it." The beatings always were administered by Kowalski, the girl said.

Once Eric was forced to go to school in pajamas and slippers wearing a sign saying he was a bed-wetter, Donna said. She was made to wear a sign on her forehead reading "Dummy," she remembered.

Donna and Eric said they still loved their mother and telephoned or wrote letters often. But Donna said she felt hurt when she learned that her mother had given birth by artificial insemination by reading National Enquirer.

"I don't want to hurt her; she is my mother. I love her. I respect her," Donna said.

The children said their mother loved children and had held jobs with day care of pre-school youngsters.

In May, when the sperm bank, known as the Repository for Germinal Choice, announced the birth, a spokesman did not identify the mother but said she had a high IQ and was "quite charming." The father was described only as "an eminent mathematician," though not a Nobel laureate.