Jeanne S. Chall, 78, an influential psychologist whose research on reading opposed the educational tide and led to her unwavering belief in the importance of phonics, died Nov. 27 at her home in Cambridge, Mass. She had a heart ailment.

She was a Harvard University professor emeritus and the author of several well-regarded texts on reading. She was best known for her staunch support of phonics instruction, an unpopular position during the past two decades when the nation's schools were dominated by the "whole-language" approach: teaching reading primarily through contextual clues rather than alphabetic decoding.

In the 1960s, when she undertook a massive review of reading research, Dr. Chall thought the scholarly scales would tip in whole language's favor. But the research seemed to prove otherwise. Her 1967 book, "Learning to Read: The Great Debate," was a definitive analysis of reading research that argued for the critical importance of teaching children phonics.

After virulent debate over the proper way to engage young children in the task of reading, public schools around the nation have begun to reintroduce phonics instruction, along with vocabulary and spelling drills, to reverse a pattern of weak performance on national tests of reading competency.

Dr. Chall's research helped demonstrate that knowledge of the alphabet and awareness of the sounds that make up words are among the most powerful predictors of reading success.

By the mid-1990s, as dismal reading scores rang alarm bells nationwide, her work was reissued in paperback, sought by a new generation of educators eager for guidance in what had become a hotly political debate.

"Learning to Read" was unequivocal in stating the case for phonics: "At every level tested -- kindergarten through college -- letter and phonics knowledge is positively associated with reading achievement and also spelling," she wrote. "At the college level, particularly among poor readers, knowing sound values of letters has an important relationship to reading ability."

Dr. Chall was born in Poland and raised in New York, where she spoke Yiddish until learning English in the New York public schools.

She was a 1941 cum laude graduate of the City College of New York and received master's and doctoral degrees from Ohio State University.

She taught at Ohio State, City College and Columbia University's Teachers College before joining Harvard's Graduate School of Education as a full professor in 1965. She took emeritus status in 1991.

Dr. Chall founded the Harvard Reading Laboratory and was an early adviser to the creators of the PBS series "Sesame Street." She also developed an important diagnostic tool for reading specialists with her Ohio State University mentor, Edgar Dale. Called the Dale-Chall Readability Formula, it was one of the first and most effective tools for measuring the difficulty of a text.