Now we know how some Senate staffers keep busy during Congress' summer recess.

A new study monitored the Wikipedia pages of U.S. senators and found that negative facts added to their biographies were deleted much faster than positive facts.

Wikipedia is the online encyclopedia that can be edited by its millions of users. There have been many documented cases of congressional staffers sprucing up their boss's biographies on Wikipedia. The website even has an entry dedicated to the subject.

The study didn't determine who removed the negative facts, but it did track how long it took for the information to be deleted.

The study was done by two , one at the University of California and one at Yale University. It was published on the website, PLOS ONE.

In the summer and fall of 2014—right before congressional elections—researchers gathered two verifiable facts about each senator that were not already on their Wikipedia pages. One fact was complimentary and the other was negative.

Researchers then added the facts to senators' Wikipedia pages and tracked whether they were removed.

An example of positive information used by researchers: During the government shutdown in 2013, Sen. Heidi Heitkamp, D-N.D., donated about $8,000 of her salary to North Dakota charities.

An example of negative information: The Annenberg Public Policy Center (Factcheck.org) has accused Sen. Patty Murray, D-Wash., of lying to voters by insisting that if they liked their , they would be able to keep it.

The results: Negative facts were 36 percent more likely to be removed within 12 hours and 29 percent more likely to be removed within three days.

"We find strong evidence of an editorial bias toward positivity," the study said.

The results were consistent across party lines, for longtime senators and newer ones, for those from big states and those from small states.

But when researchers did the experiment on former senators who no longer held public office, they found that positive and negative facts were removed at about the same rate.

"Our findings suggest the editorial bias is limited to active politicians, the types of people for whom the stakes of a positive public image are the highest," the study said.

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Unhappy about a congressional investigation you consider one-sided and want to see halted? When you're a member of the minority party in the House, you can complain about it and ... well, that's about it.

That's where House Democrats find themselves as four congressional committees investigate Planned Parenthood and secretly recorded videos showing the group's officials talking about giving fetal tissue to medical researchers.

Those videos were produced by a group of anti-abortion activists calling themselves the Center for Medical Progress. Democrats want the congressional committees to suspend their investigations or to also probe the center, which Planned Parenthood says is a bunch of ideologues who have released misleadingly edited tapes.

The center "may have violated numerous state and federal laws in their clandestine effort to roll back the rights of millions of women" seeking care from Planned Parenthood, Reps. Elijah Cummings, D-Md., and John Conyers, D-Mich., wrote in a letter Thursday.

The center has already become a target of U.S. Attorney General Loretta Lynch, whose office says the group hasn't paid required fees or submitted certain IRS forms. It is also under investigation by Democratic Attorney General Kamala Harris of California, where the center lists its address.

The Democrats' letter went to Reps. Bob Goodlatte, R-Va., and Jason Chaffetz, R-Utah, who respectively chair the House Judiciary and Government Reform committees. Both chairmen made clear they'll keep moving ahead.

"Our investigation will continue to ensure that no federal funds were used in potentially illegal activity involving fetal tissue at any Planned Parenthood facility or affiliate," said MJ Henshaw, spokeswoman for the Oversight panel.

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House Republicans from contested districts who want financial and logistical help have been able to get it from the National Republican Congressional Committee, the House GOP's political arm.

Now, it turns out that in exchange, some of them have to sign a detailed memorandum of understanding that promises to give the committee a detailed description of their legislative agenda and the political rational behind it.

The memo, first obtained by The Washington Post, must be signed for lawmakers to join the committee's Patriot Program, which lists 23 vulnerable members it is helping. Lawmakers must agree to do more than a dozen things, including raising at least $100,000 for the NRCC this year, using staff and vendors who meet NRCC standards and reporting on plans for campaign events and demographic targets.

Also required: "Detailed, written legislative strategy that provides short, intermediate and long-term legislative goals, including political justifications for those goals. Be sure to include local issues unique to the district or region," the memo says.

Democrats suggested that the GOP has gone too far. Spokeswoman Meredith Kelly of the Democratic Congressional Campaign Committee said the House Democratic political operation makes sure its candidates run smart campaigns "but would never require submission and approval of a legislative agenda, especially in exchange for financial and political support."

NRCC spokeswoman Katie Martin said the question about legislative agendas "is for informational purposes only to know what members are interested in or going to be advocating for."

More information: Wikipedia study: tinyurl.com/opp86st

Journal information: PLoS ONE