And Thomas D. Lyon, a law and psychology professor at the University of Southern California whom Professor Cheit quotes approvingly, told me, “We may still make mistakes, but we know what we should be doing.”

Interviewers have moved from closed-ended questions to open-ended ones. The simple “Tell me why you came to speak with me” elicits disclosures from the majority of children who report abuse, according to one study. “What happened?” or “How did you feel?” can prompt children to give details on their own, without being fed suggestions.

Some of the critical work on suggestibility, which helped lead to the improved interviewing techniques, was conducted by two prominent psychologists whom Professor Cheit sharply criticizes: Stephen J. Ceci of Cornell and Maggie Bruck of Johns Hopkins. They found that if they interviewed ordinary children using the old technique of leading questions, a substantial minority would play along, embellishing a fanciful tale even though it was false. Professor Cheit argues that the importance of this finding has been exaggerated.

He is an outlier here. But there is some dispute in the field about a related question: whether parents who suspect abuse are prone to question a child in a way that introduces suggestibility, so that later even a properly conducted interview might produce a false report.

“That’s where the serious disagreement is now: How easy is it to create a story the child will maintain when questioned in a legitimate way?” Dr. Lyon said. (This differs from the debate over repressed memories — claims by adults about remembering abuse they did not disclose as children.)

Dr. Lyon’s main conclusion from the research is that it takes skill to implant a fabricated story. “We find parents, left to their own devices, are lousy at creating false reports,” he said.

Dr. Bruck, on the other hand, remains concerned about the influence of parents. “All these day-care cases, they all started with parents questioning their children,” she said.