The panel dismissed the idea, notably advanced last year by Lawrence H. Summers, then the president of Harvard, that the relative dearth of women in the upper ranks of science might be the result of “innate” intellectual deficiencies, particularly in mathematics.

If there are any cognitive differences, the report says, they are small and irrelevant. In any event, the much-studied gender gap in math performance has all but disappeared as more and more girls enroll in demanding classes. Even among very high achievers, the gap is narrowing, the panelists said.

A spokesman for Mr. Summers said he was out of the country and could not be reached for comment.

Nor is the problem a lack of women in the academic pipeline, the report says. Though women leave science and engineering more often than men “at every educational transition” from high school through college professorships, the number of women studying science and engineering has sharply increased at all levels.

For 30 years, the report says, women have earned at least 30 percent of the nation’s doctorates in social and behavioral sciences, and at least 20 percent of the doctorates in life sciences. Yet they appear among full professors in those fields at less than half those levels. Women from minorities are “virtually absent,” it adds.

The report also dismissed other commonly held beliefs — that women are uncompetitive or less productive, that they take too much time off for their families, and so on. Their real problems, it says, are unconscious but pervasive bias, “arbitrary and subjective” evaluation processes, and a work environment in which “anyone lacking the work and family support traditionally provided by a ‘wife’ is at a serious disadvantage.”