‘Like’ This Article Online? Your Friends Will Probably Approve, Too, Scientists Say

But surprisingly, an unfair negative reaction will not spur others to dislike the article. Instead, a thumbs-down view will soon be counteracted by thumbs up from other readers.

Those are the implications of new research looking at the behavior of thousands of people reading online comments, scientists reported Friday in the journal Science. A positive nudge, they said, can set off a bandwagon of approval.

“Hype can work,” said one of the researchers, Sinan K. Aral, a professor of information technology and marketing at the Massachusetts Institute of Technology, “and feed on itself as well.”

If people tend to herd together on popular opinions, that could call into question the reliability of “wisdom of the crowd” ratings on Web sites like Yelp or Amazon and perhaps provide marketers with hints on how to bring positive attention to their products.

“This is certainly a provocative study,” said Matthew O. Jackson, a professor of economics at Stanford who was not involved with the research. “It raises a lot of questions we need to answer.”

Besides Dr. Aral (who is also a scholar in residence at The New York Times research and development laboratory, working on unrelated projects), the researchers are from Hebrew University in Jerusalem and New York University.

They were interested in answering a question that long predates the iPhone and Justin Bieber: Is something popular because it is actually good, or is it popular just because it is popular?

To help answer that question, the researchers devised an experiment in which they could manipulate a small corner of the Internet: reader comments.

They collaborated with an unnamed Web site, the company did not want its involvement disclosed, on which users submit links to news articles. Readers can then comment on the articles, and they can also give up or down votes on individual comments. Each comment receives a rating calculated by subtracting negative votes from positive ones.

The experiment performed a subtle, random change on the ratings of comments submitted on the site over five months: right after each comment was made, it was given an arbitrary up or down vote, or — for a control group — left alone. Reflecting a tendency among the site’s users to provide positive feedback, about twice as many of these arbitrary initial votes were positive: 4,049 to 1,942.

The first person reading the comment was 32 percent more likely to give it an up vote if it had been already given a fake positive score. There was no change in the likelihood of subsequent negative votes. Over time, the comments with the artificial initial up vote ended with scores 25 percent higher than those in the control group.

“That is a significant change,” Dr. Aral said. “We saw how these very small signals of social influence snowballed into behaviors like herding.”

Meanwhile, comments that received an initial negative vote ended up with scores indistinguishable from those in the control group.

The Web site allows users to say whether they like or dislike other users, and the researchers found that a commenter’s friends were likely to correct the negative score while enemies did not find it worth their time to knock down a fake up vote.

The distortion of ratings through herding is not a novel concern. Reddit, a social news site that said it was not the one that participated in the study, similarly allows readers to vote comments up or down, but it also allows its moderators to hide those ratings for a certain amount of time. “Now a comment will more likely be voted on based on its merit and appeal to each user, rather than having its public perception influence its votes,” it explained when it unveiled the feature in April.

Duncan J. Watts, a scientist at Microsoft Research, said the overall findings fit with “cumulative advantage,” the idea that something that starts slightly more popular will build upon that popularity until it is far ahead of its competitors — and conversely, something that does not catch on will usually fade away whether or not it is good.

He cited the new crime novel “The Cuckoo’s Calling,” by Robert Galbraith, which received good reviews but tiny sales when it was released in April. When it was revealed that Galbraith was a pseudonym for J. K. Rowling, the book suddenly had the cumulative advantage conferred by the Harry Potter series and jumped to the top of best-seller lists.

“The biggest obstacle to success is just being noticed,” Dr. Watts said.

But opinions do not invariably follow popularity. In an earlier experiment by Dr. Watts, people listened to a list of songs ranked by popularity and were asked to rate them. But for some, the list was inverted — what they were told was the most popular song was actually the least popular.

The incorrect list did affect how listeners rated the songs — the good songs never achieved the same popularity as among listeners who were given the correct list, and the bad songs did better than they would have otherwise.

“But we also found, in a result that was somewhat consistent with the result here, that sometimes the songs were able to recover their sort of real ranking in spite of the manipulation,” Dr. Watts said. The listeners, he said, “in effect noticed that the song was better or worse than we had made it seem.”

Brains as Clear as Jell-O for Scientists to Explore

Scientists at Stanford University reported on Wednesday that they have made a whole mouse brain, and part of a human brain, transparent so that networks of neurons that receive and send information can be highlighted in stunning color and viewed in all their three-dimensional complexity without slicing up the organ.

Even more important, experts say, is that unlike earlier methods for making the tissue of brains and other organs transparent, the new process, called Clarity by its inventors, preserves the biochemistry of the brain so well that researchers can test it over and over again with chemicals that highlight specific structures and provide clues to past activity. The researchers say this process may help uncover the physical underpinnings of devastating mental disorders like schizophrenia, autism, post-traumatic stress disorder and others.

The work, reported on Wednesday in the journal Nature, is not part of the Obama administration’s recently announced initiative to probe the secrets of the brain, although the senior author on the paper, Dr. Karl Deisseroth at Stanford, was one of those involved in creating the initiative and is involved in planning its future.

Dr. Thomas Insel, director of the National Institute of Mental Health, which provided some of the financing for the research, described the new work as helping to build an anatomical “foundation” for the Obama initiative, which is meant to look at activity in the brain.

Dr. Insel added that the technique works in a human brain that has been in formalin, a preservative, for years, which means that long-saved human brains may be studied. “Frankly,” he said, “that is spectacular.”

Kwanghun Chung, the primary author on the paper, and Dr. Deisseroth worked with a team at Stanford for years to get the technique right. Dr. Deisseroth, known for developing another powerful technique, called optogenetics, that allows the use of light to switch specific brain activity on and off, said Clarity could have a broader impact than optogenetics. “It’s really one of the most exciting things we’ve done,” he said, with potential applications in neuroscience and beyond.

“I think it’s great,” said Dr. Clay Reid, a senior investigator at the Allen Institute for Brain Science in Seattle, who was not involved in the work. “One of the very difficult challenges has been making the brain, which is opaque, clear enough so that you can see deep into it.” This technique, he said, makes brains “extremely clear” and preserves most of the brain chemistry. “It has it all,” he said.

In the mid-2000s, a team led by Dr. Jeff Lichtman at Harvard developed a process called Brainbow to breed mice that are genetically altered to make their brain neurons fluoresce in many different colors. The new technique would allow whole brains of those mice with their rainbow neurons to be preserved and studied.

“I’m quite excited to try this,” Dr. Lichtman said.

There are several ways to make tissue transparent. The key to the new technique is a substance called a hydrogel, a material that is mostly water held together by larger molecules to give it some solidity.

Dr. Chung said the hydrogel forms a kind of mesh that permeates the brain and connects to most of the molecules, but not to the lipids, which include fats and some other substances. The brain is then put in a soapy solution and an electric current is applied, which drives the solution through the brain, washing out the lipids. Once they are out, the brain is transparent, and its biochemistry is intact, so it may be infused with chemicals, like antibody molecules that also have a dye attached, that show fine details of its structure and previous activity.

Techniques like this, said Dr. Insel, “should give us a much more precise picture of what is happening in the brains of people who have schizophrenia, autism, post-traumatic stress disorder, bipolar disorder and depression.”

The tricky part was getting the right combination of temperature, electricity and solution. And it was very tricky indeed, said Dr. Chung. Over the course of years spent trying to make it work, he said, “I burned and melted more than a hundred brains.”

But with the paper’s publication, the recipe is now available to anyone who wants to use it, and, he said, “I think it will be relatively easy.”

The technique has its limits, of course. Dr. Chung said more work needed to be done before it could be applied to a whole human brain, because a human’s brain is so much larger than a mouse’s, and has more lipids.

Dr. Chung said he planned to start his own lab soon and to work on refining the technology. But he pointed out that it is already known that it works on all tissue, not just brains, and can be used to look for structures other than nerve cells. On his laboratory bench, he said, “I have a transparent liver, lungs and heart.”

Dr. Reid agreed that Clarity had applications in many fields. “It could permeate biology,” he said.

This article has been revised to reflect the following correction:

Correction: April 10, 2013

An earlier version of this article misstated Dr. Clay Reid’s work with Dr. Jeff Lichtman of Harvard. Dr. Reid was involved in Dr. Lichtman’s Connectome Project, not on the Brainbow team.

Bits Blog: Scientists Uncover Invisible Motion in Video

A 30-second video of a newborn baby shows the infant silently snoozing in its crib, his breathing barely perceptible. But when the video is run through an algorithm that can amplify both movement and color, the baby’s face blinks crimson with each tiny heartbeat.

The amplification process is called Eulerian Video Magnification, and is the brainchild of a team of scientists at the Massachusetts Institute of Technology’s Computer Science and Artificial Intelligence Laboratory.

The team originally developed the program to monitor neonatal babies without making physical contact. But they quickly learned that the algorithm can be applied to other videos to reveal changes imperceptible to the naked eye. Prof. William T. Freeman, a leader on the team, imagines its use in search and rescue, so that rescuers could tell from a distance if someone trapped on a ledge, say, is still breathing.

“Once we amplify these small motions, there’s like a whole new world you can look at,” he said.

The system works by homing in on specific pixels in a video over the course of time. Frame-by-frame, the program identifies minute changes in color and then amplifies them up to 100 times, turning, say, a subtle shift toward pink to a bright crimson. The scientists who developed it believe it could also have applications in industries like manufacturing and oil exploration. For example, a factory technician could film a machine to check for small movements in bolts that might indicate an impending breakdown. In one video presented by the scientists, a stationary crane sits on a construction site, so still it could be a photograph. But once run through the program, the crane appears to sway precariously in the wind, perhaps tipping workers off to a potential hazard.

It is important to note that the crane does not actually move as much as the video seems to show. It is the process of motion amplification that gives the crane its movement.

The program originally gained attention last summer when the team presented it at the annual computer graphics conference known as Siggraph in Los Angeles.

Since then, the M.I.T. team has improved the algorithm to achieve better quality results, with significant improvements in clarity and accuracy.

Michael Rubinstein, a doctoral student and co-author on the project, said that after the presentation and subsequent media coverage, the team was inundated with e-mails inquiring about the availability of the program for uses ranging from health care to lie detection in law enforcement. Some people, says Mr. Rubinstein, inquired about how the program might be used in conjunction with Google’s glasses to see changes in a person’s face while gambling.

“People wanted to be able to analyze their opponent during a poker game or blackjack and be able to know whether they’re cheating or not, just by the variation in their heart rate,” he said.

The team posted the code online and made it available to anyone who wanted to download it and run the program. But to do so required some technical expertise because the interface was not simple to use. Last week, Quanta Research Cambridge, a Taiwan-based manufacturer of laptop computers that helped finance the project, provided a way for people to upload video clips to their Web site and to see a video that is run through the program.

The project is also financed by the National Science Foundation and Royal Dutch Shell, among others.

The team is also working toward making the program as an app for smartphones. “I want people to look around and see what’s out there in this world of tiny motions,” said Mr. Freeman.