Howard Gruber, who died January 25 at age 82, was a psychologist and expert in the study of the creative process.

His 1974 study of Charles Darwin, “Darwin on Man,” in which he documented from original notebooks the thought processes that culminated in the theory of natural selection, was named by American Scientist as one of the 100 most important science books of the 20th century.

Gruber was a disciple of a Swiss developmental psychologist, Jean Piaget; late in his career, Gruber took over the University of Geneva chair in psychology once held by his mentor.

Gruber grew up in Brooklyn and attended Brooklyn College; his father was a waiter at Lindy’s. Service in the Army during World War II took him to the Philippines and later to Japan, where he was part of the American occupation force.

After graduating from Cornell University with a Ph.D. in clinical psychology, Gruber taught at the University of Colorado at Denver and then at the Newark, N.J., campus of Rutgers, where he was founder and director of the Institute for Cognitive Studies.

Gruber was attracted early to the work of Piaget, who showed that young children follow predictable stages in recognition of shapes and numbers of objects and the like. It was Gruber who first thought to demonstrate object-permanence – the mental ability to perceive that a hidden object still exists – in kittens.

He also developed a method for studying why the moon appears larger on the horizon than when it is directly overhead; it was published in Science in 1962.

In “Darwin on Man,” Gruber rejected the notion that creativity is a lighting bolt-like instant of recognition. Instead, by looking at Darwin’s scientific process through a painstaking reading of the notebooks, Gruber demonstrated that natural selection was the result of a continual process of reevaluating

data and testing new ideas against them. The gradualist notion of creativity – which also rejected the fashionable idea that creativity was simply a reflection of society – was entirely consistent with Piaget.

With Jacques Voneche, Gruber published “The Essential Piaget” (1977), a collection of writings. With his wife, Doris Wallace, he edited “Creative People at Work” (1989), a dozen studies of individuals, including Piaget, William Wordsworth, Albert Einstein, and Anais Nin.

A self-described socialist since his college days, when the Spanish Civil War topped the activist agenda, Gruber spoke out strongly throughout his career on issues of war and peace. During the Vietnam War, he was listed among two-dozen prominent professors backing Moratorium Day, a national student strike supported by John Kenneth Galbraith and Noam Chomsky. He was founder and chairman of Psychologists for Social Action, and in 1982 hosted a conference at City University titled “Social Scientists Against Nuclear War.”

Occasionally, Gruber’s activism took on a less political form. When some junior high school students on Long Island in 1969 decided to simulate the voyage of Apollo 9 by spending five days inside a wooden mockup, Gruber indignantly phoned their teacher to protest. “Dr. Gruber was said to have warned that it was ‘irresponsible’ to confine children in such a small space for such a long period,” the Times reported. “The sudden ‘abort’ of the mission … left the three boys disappointed and their science teacher … close to tears.”

A collection of Gruber’s papers is due to be published later this year, Ms. Wallace said.

Howard Ernest Gruber

Born November 6, 1922, at Brooklyn; died January 25 of pneumonia following a lengthy illness at a New York nursing facility; survived by his wife, Doris Wallace, his children, Simon and Sarah, and three grandchildren.