Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Good ratings gone bad: study shows recommender systems can manipulate users’ opinions

04.04.2003


Study also reports users lose trust in systems that give phony ratings

Online "recommender systems" are used to suggest highly rated selections for book buyers, movie renters or other consumers, but a new study by University of Minnesota computer science researchers shows for the first time that a system that lies about ratings can manipulate users’ opinions. Over time, however, users lose trust in unscrupulous systems.

The Minnesota research group, led by professors Joseph Konstan and John Riedl, conducted experiments with MovieLens, a member driven movie recommendation Web site, which the Minnesota team created to put their research on recommender systems into practice. The results of their latest studies will be presented at the CHI 2003 Conference on Human Factors in Computing Systems, April 5-10, 2003, in Fort Lauderdale, Fla. The work is supported by the National Science Foundation, the independent federal agency that supports basic research in all fields of science and engineering.

The results suggest that "shills," who flood recommender systems with artificially high (or low) ratings, can have an impact and that recommender systems will take longer than previously expected to self-correct. The idea behind self-correction is that misled users will come back and give the item in question a more accurate rating.

"This study isn’t about defending against shill attacks, but about trust in the system," Konstan said. "Our results show that individual shilling will take longer to correct, but the larger impact is the loss of trust in the system." In the Minnesota study, users were sensitive to the quality of the predictions and expressed dissatisfaction when the system gave inaccurate ratings.

Taken together, the experiments provide several tips for the designers of interfaces to recommender systems. Interfaces should allow users to concentrate on rating while ignoring predictions. Finer-grained rating scales are preferred over simple "thumbs up, thumbs down" scales, but are not essential to good predictions. Finally, because users are sensitive to manipulation and inaccurate predictions, to keep customers happy, no recommender system at all is better than a bad recommender system.

Many online shopping sites use recommender systems to help consumers cope with information overload and steer consumers toward products that might interest them. Recommender systems based on "collaborative filtering" generate recommendations based on a user’s selections or ratings and the ratings of other users with similar tastes.

The CHI 2003 paper reports the results of three experiments that attempted to shed light on questions such as "Can the system make a user rate a ’bad’ movie ’good’?" "Do users notice when predictions are manipulated?" "Are users consistent in their ratings?" and "How do different rating scales affect users’ ratings?"

"To our knowledge, no one has studied how recommendations affect users’ opinions," Konstan said. "We thought it was a socially important question because many of these systems are used in commercial applications. We found that if the system lies you can gain some influence in the short term, but you lose trust in the long term. This is a lot like trust between humans."

In the first experiment, users re-rated movies while presented with some "predictions" that were different from the user’s prior rating of the movie. In the second experiment, users rated movies they hadn’t rated before. Some users saw "predictions" that were skewed higher or lower, while a control group saw only the system’s accurate predictions. The final experiment had users re-rate movies using three different rating scales and asked users their opinions of the different scales. In the re-rating experiment, users were generally consistent, but they did tend to change their rating in the direction of the system’s skewed "prediction." In fact, users could even be influenced to change a rating from negative to positive or vice versa. When users rated previously unrated movies, they tended to rate toward the system’s prediction, whether it was skewed or not.

Konstan also noted that, while this study used movie ratings, recommender systems have much wider application. Such systems can also be used for identifying highly rated research papers from a given field or for knowledge management in large enterprises. New employees, for example, can bring themselves up to speed by focusing on highly rated news items or background materials.

David Hart | National Science Foundation
Further information:
http://www.movielens.umn.edu/
http://www.nsf.gov

More articles from Communications Media:

nachricht New cruise ship “Mein Schiff 1” features Fraunhofer 3D sound on board
05.09.2018 | Fraunhofer-Institut für Digitale Medientechnologie IDMT

nachricht Small enclosure, big sound, clear speech
31.08.2018 | Fraunhofer-Institut für Digitale Medientechnologie IDMT

All articles from Communications Media >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland

15.11.2018 | Earth Sciences

When electric fields make spins swirl

15.11.2018 | Physics and Astronomy

Discovery of a cool super-Earth

15.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>