* Most importantly, from the Times: Strictly on the basis of significance — a statistical measure of how likely it is that a result did not occur by chance — 35 of the studies held up, and 62 did not. (Three were excluded because their significance was not clear.) The overall “effect size,” a measure of the strength of a finding, dropped by about half across all of the studies. Yet very few of the redone studies contradicted the original ones; their results were simply weaker.
* Also: The research team also measured whether the prestige of the original research group, rated by measures of expertise and academic affiliation, had any effect on the likelihood that its work stood up. It did not.
* And: The only factor that did [affect the likelihood of successful reproduction] was the strength of the original effect — that is, the most robust findings tended to remain easily detectable, if not necessarily as strong.
* Finally: The project’s authors write that, despite the painstaking effort to duplicate the original research, there could be differences in the design or context of the reproduced work that account for the different findings. Many of the original authors certainly agree.
* According to several experts, there is no reason to think the problems are confined to psychology, and it could be worse in other fields. The researchers chose psychology merely because that is their field of expertise.
* I haven't seen anything indicating the 100 studies are a representative sample of the population of published research, and at least one scientist raised this question.