Dr. Hauser is a fluent and persuasive writer, and his undoing seems to have been his experiments, many of which depended on videotaping cotton-topped tamarin monkeys and noting their responses. It is easy for human observers to see the response they want and so to be fooled by the monkeys.

Dr. Terrace said there had been problems for some time with Dr. Hauser’s work.

“First there was arbitrary interpretation of the videotapes to suit the hypothesis,” he said. “The other was whether the data was real. There have been a number of papers using videotape, and all of them have to be reviewed to see if the data holds up.”

Dr. Terrace noted that it was easy for a researcher to see what he wanted in a videotaped animal’s reactions, and that independent observers must check every finding.

In one case, according to an article in The Boston Globe on Tuesday, Gordon G. Gallup Jr. of the State University of New York at Albany asked Dr. Hauser for videotapes of an experiment in which cotton-topped tamarins were said to recognize themselves in a mirror. When he received the videotapes, Dr. Gallup could see no evidence that this was the case. Dr. Gallup did not return a call or respond to e-mail on Wednesday.

Dr. Hauser’s 2002 article in Cognition was published with two co-authors, but he has accepted responsibility for the error. One co-author, Gary Marcus of New York University, said he saw the summary of Dr. Hauser’s experiments but not the raw data. He was informed that there was a problem with the data, but has not seen the result of the investigation.

Mr. Neal, Harvard’s press officer, declined to say when the university’s examination of Dr. Hauser’s laboratory had started, when it was completed or how many other papers besides that in Cognition were under question.