Scientific studies about how people act or think can rarely be replicated by outside experts, according to a study that raises new questions about the seriousness of psychology research.
A team of 270 scientists tried reproducing 100 psychology and social science studies that had been published in three top peer-reviewed US journals in 2008.
Just 39 percent came out with same results as the initial reports, said the findings in the journal Science.
The study topics ranged from people's social lives and interactions with others to research involving perception, attention and memory.
No medical therapies were called into question as a result of the study, although a separate effort is underway to evaluate cancer biology studies.
"It's important to note that this somewhat disappointing outcome does not speak directly to the validity or the falsity of the theories," said Gilbert Chin, a psychologist and senior editor at the journal Science.
"What it does say is that we should be less confident about many of the original experimental results."
Study co-author Brian Nosek from the University of Virginia said the research shows the need for scientists to continually question themselves.
"A scientific claim doesn't become believable because of the status or authority of the person that generated it," Nosek told reporters.
Nosek said scientists are also under pressure to publish their research regularly and in top journals, and the process can lead to a skewed picture.