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 Between filter bubbles, uneven visibility and transnationality
06.12.2017 | Schweizerischer Nationalfonds SNF

nachricht New Technologies for A/V Analysis and Search
13.04.2017 | 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: Error-free into the Quantum Computer Age

A study carried out by an international team of researchers and published in the journal Physical Review X shows that ion-trap technologies available today are suitable for building large-scale quantum computers. The scientists introduce trapped-ion quantum error correction protocols that detect and correct processing errors.

In order to reach their full potential, today’s quantum computer prototypes have to meet specific criteria: First, they have to be made bigger, which means...

Im Focus: Search for planets with Carmenes successful

German and Spanish researchers plan, build and use modern spectrograph

Since 2016, German and Spanish researchers, among them scientists from the University of Göttingen, have been hunting for exoplanets with the “Carmenes”...

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

The body's street sweepers

18.12.2017 | Life Sciences

Fast flowing heat in layered material heterostructures

18.12.2017 | Materials Sciences

Life on the edge prepares plants for climate change

18.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>