When searching online for a new gadget to buy or a movie to rent, many people pay close attention to the number of stars awarded by customer-reviewers on popular websites. But new research confirms what some may already suspect: those ratings can easily be swayed by a small group of highly active users.

Kostakos studied voting patterns on Amazon, the Internet Movie Database (IMDb), and the book review site BookCrossings. The research was presented last month at the 2009 IEEE International Conference on Social Computing. His team looked at hundreds of thousands of items and millions of votes across the three sites. In each case, they found that a small number of users accounted for a large number of ratings. For example, only 5 percent of active Amazon users cast votes on more than 10 products. A handful of users voted hundreds of items.

“If you have two or three people voting 500 times,” says Kostakos, the results may not be representative of the community overall. He suspects this may be why ratings often tend toward extremes.

Jahna Otterbacher, a lecturer at the University of Cyprus who studies online rating systems, says that previous research has hinted that rating systems can be skewed by factors such as the age of participants. But she notes that some sites, including Amazon, already incorporate mechanisms designed to control the quality of ratings–for example, allowing users to vote on the helpfulness of other users’ reviews.

Kostakos proposes further ways to make recommendations more reliable. He suggests, fo making it easier to vote, in order to encourage more users to join in, and waiting until an item has received a certain number of ratings before showing them.

Kostakos also suggests removing overly negative and overly positive reviews, so a site won’t be too positive or too negative overall. But Otterbacher, who is examining reviews from IMDb, Amazon, and Yelp, worries that such a policy could discourage many people from taking part. “People who write reviews want to say something about the item, and they can be pretty passionate about their opinions,” she says.

Some futurists such as Ray Kurzweil have hypothesized that we will someday soon pass through a singularity–that is, a time period of rapid technological change beyond which we cannot envision the future of society. Most visions of this singularity focus on the creation of machines intelligent enough to devise machines even more intelligent than themselves, and so forth recursively, thus launching a positive feedback loop of intelligence amplification. It’s an intriguing thought. (One of the first things I wanted to do when I got to MIT as an undergraduate was to build a robot scientist that could make discoveries faster and better than anyone else.) Even the CTO of Intel, Justin Rattner, has publicly speculated recently that we’re well on our way to this singularity, and conferences like the Singularity Summit (at which I’ll be speaking in October) are exploring how such transformations might take place.

As a brain engineer, however, I think that focusing solely on intelligence augmentation as the driver of the future is leaving out a critical part of the analysis–namely, the changes in motivation that might arise as intelligence amplifies. Call it the need for “machine leadership skills” or “machine philosophy”–without it, such a feedback loop might quickly sputter out.

We all know that intelligence, as commonly defined, isn’t enough to impact the world all by itself. The ability to pursue a goal doggedly against obstacles, ignoring the grimness of reality (sometimes even to the point of delusion–i.e., against intelligence), is also important. Most science-fiction stories prefer their artificial intelligences to be extremely motivated to do things–for example, enslaving or wiping out humans, if The Matrix and Terminator II have anything to say on the topic. But I find just as plausible the robot Marvin, the superintelligent machine from Douglas Adams’ The Hitchhiker’s Guide to the Galaxy, who used his enormous intelligence chiefly to sit around and complain, in the absence of any big goal.

Social networks are rife with examples of users failing to understand the privacy implications of posting sensitive information online.

In February, for example, school officials in Wisconsin suspended a teacher who posted on Facebook a picture of herself pointing a gun at the camera. In April, the Swiss insurance company Nationale Suisse fired an employee after she called in sick and then posted updates on the same site. Others have raised concerns about users handing so much personal information to social-networking companies themselves.

Now, researchers at the University of Waterloo in Ontario have developed a browser plug-in to help users keep their information private from prying eyes and from social-network providers as well. Urs Hengartner, an assistant professor of computer science, and his colleagues say the plug-in replaces sensitive information in a user’s profile and news feed with meaningless text that can only be unscrambled by trusted friends or contacts. Dubbed FaceCloak, the tool assures its users that sensitive data stays private, Hengartner says. “If you have a particular illness, you might want to allow only your friends to see that,” he says. “This leaves it up to the user to decide what information to keep away from Facebook.”

The tool is the latest shot in a battle between social networks and privacy-conscious users. Most users of Facebook, MySpace, and other social networks remain unaware of the privacy implications of posting personal information to such sites, says Alessandro Acquisti, an associate professor of information systems and public policy at Carnegie Mellon University.

Today’s solar cells lose much of the energy in light to heat. Now researchers at Cornell University have made a photovoltaic cell out of a single carbon nanotube that can take advantage of more of the energy in light than conventional photovoltaics. The tiny carbon tubes might eventually be used to make more-efficient next-generation solar cells.

“The main limiting factor in a solar cell is that when you absorb a high-energy photon, you lose energy to heat, and there’s no way to recover it,” says Matthew Beard, a senior scientist at the National Renewable Energy Laboratory in Golden, CO. Loss of energy to heat limits the efficiency of the best solar cells to about 33 percent. “The material that can convert at a much higher efficiency will be a game-changer,” says Beard.

Researchers led by Paul McEuen, professor of physics at Cornell, began by putting a single nanotube in a circuit and giving it three electrical contacts called gates, one at each end and one underneath. They used the gates to apply a voltage across the nanotube, then illuminated it with light. When a photon hits the nanotube, it transfers some of its energy to an electron, which can then flow through the circuit off the nanotube. This one-photon, one-electron process is what normally happens in a solar cell. What’s unusual about the nanotube cell, says McEuen, is what happens when you put in what he calls “a big photon” — a photon whose energy is twice as big as the energy normally required to get an electron off the cell. In conventional cells, this is the energy that’s lost as heat. In the nanotube device, it kicks a second electron into the circuit. The work was described last week in the journal Science.

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