Matrix Factorization Techniques for Recommender Systems

Personalized recommendation benefits users in accessing contents of interests effectively. Current research on recommender systems mostly focuses on matching users with proper items based on user interests. However, significant efforts are missing to understand how the recommendations influence user preferences and behaviors, e.g., if and how recommendations result in \textit{echo chambers}. Extensive efforts have been made in examining the phenomenon in online media and social network systems. Meanwhile, there are growing concerns that recommender systems might lead to the self-reinforcing of user's interests due to narrowed exposure of items, which may be the potential cause of echo chamber. In this paper, we aim to analyze the echo chamber phenomenon in Alibaba Taobao -- one of the largest e-commerce platforms in the world. Echo chamber means the effect of user interests being reinforced through repeated exposure to similar contents. Based on the definition, we examine the presence of echo chamber in two steps. First, we explore whether user interests have been reinforced. Second, we check whether the reinforcement results from the exposure of similar contents. Our evaluations are enhanced with robust metrics, including cluster validity and statistical significance. Experiments are performed on extensive collections of real-world data consisting of user clicks, purchases, and browse logs from Alibaba Taobao. Evidence suggests the tendency of echo chamber in user click behaviors, while it is relatively mitigated in user purchase behaviors. Insights from the results guide the refinement of recommendation algorithms in real-world e-commerce systems.

Understanding Echo Chambers in E-commerce Recommender Systems

Personalized recommendation benefits users in accessing contents of interests effectively. Current research on recommender systems mostly focuses on matching users with proper items based on user interests. However, significant efforts are missing to understand how the recommendations influence user preferences and behaviors, e.g., if and how recommendations result in echo chambers. Extensive efforts have been made in examining the phenomenon in online media and social network systems. Meanwhile, there are growing concerns that recommender systems might lead to the self-reinforcing of user's interests due to narrowed exposure of items, which may be the potential cause of echo chamber. In this paper, we aim to analyze the echo chamber phenomenon in Alibaba Taobao --- one of the largest e-commerce platforms in the world. Echo chamber means the effect of user interests being reinforced through repeated exposure to similar contents. Based on the definition, we examine the presence of echo chamber in two steps. First, we explore whether user interests have been reinforced. Second, we check whether the reinforcement results from the exposure of similar contents. Our evaluations are enhanced with robust metrics, including cluster validity and statistical significance. Experiments are performed on extensive collections of real-world data consisting of user clicks, purchases, and browse logs from Alibaba Taobao. Evidence suggests the tendency of echo chamber in user click behaviors, while it is relatively mitigated in user purchase behaviors. Insights from the results guide the refinement of recommendation algorithms in real-world e-commerce systems.

While algorithm audits are growing rapidly in commonality and public importance, relatively little scholarly work has gone toward synthesizing prior work and strategizing future research in the area. This systematic literature review aims to do just that, following PRISMA guidelines in a review of over 500 English articles that yielded 62 algorithm audit studies. The studies are synthesized and organized primarily by behavior (discrimination, distortion, exploitation, and misjudgement), with codes also provided for domain (e.g. search, vision, advertising, etc.), organization (e.g. Google, Facebook, Amazon, etc.), and audit method (e.g. sock puppet, direct scrape, crowdsourcing, etc.). The review shows how previous audit studies have exposed public-facing algorithms exhibiting problematic behavior, such as search algorithms culpable of distortion and advertising algorithms culpable of discrimination. Based on the studies reviewed, it also suggests some behaviors (e.g. discrimination on the basis of intersectional identities), domains (e.g. advertising algorithms), methods (e.g. code auditing), and organizations (e.g. Twitter, TikTok, LinkedIn) that call for future audit attention. The paper concludes by offering the common ingredients of successful audits, and discussing algorithm auditing in the context of broader research working toward algorithmic justice.

Problematic Machine Behavior: A Systematic Literature Review of Algorithm Audits

Traditionally, machine learning algorithms relied on reliable labels from experts to build predictions. More recently however, algorithms have been receiving data from the general population in the form of labeling, annotations, etc. The result is that algorithms are subject to bias that is born from ingesting unchecked information, such as biased samples and biased labels. Furthermore, people and algorithms are increasingly engaged in interactive processes wherein neither the human nor the algorithms receive unbiased data. Algorithms can also make biased predictions, leading to what is now known as algorithmic bias. On the other hand, human’s reaction to the output of machine learning methods with algorithmic bias worsen the situations by making decision based on biased information, which will probably be consumed by algorithms later. Some recent research has focused on the ethical and moral implication of machine learning algorithmic bias on society. However, most research has so far treated algorithmic bias as a static factor, which fails to capture the dynamic and iterative properties of bias. We argue that algorithmic bias interacts with humans in an iterative manner, which has a long-term effect on algorithms’ performance. For this purpose, we present an iterated-learning framework that is inspired from human language evolution to study the interaction between machine learning algorithms and humans. Our goal is to study two sources of bias that interact: the process by which people select information to label (human action); and the process by which an algorithm selects the subset of information to present to people (iterated algorithmic bias mode). We investigate three forms of iterated algorithmic bias (personalization filter, active learning, and random) and how they affect the performance of machine learning algorithms by formulating research questions about the impact of each type of bias. Based on statistical analyses of the results of several controlled experiments, we found that the three different iterated bias modes, as well as initial training data class imbalance and human action, do affect the models learned by machine learning algorithms. We also found that iterated filter bias, which is prominent in personalized user interfaces, can lead to more inequality in estimated relevance and to a limited human ability to discover relevant data. Our findings indicate that the relevance blind spot (items from the testing set whose predicted relevance probability is less than 0.5 and who thus risk being hidden from humans) amounted to 4% of all relevant items when using a content-based filter that predicts relevant items. A similar simulation using a real-life rating data set found that the same filter resulted in a blind spot size of 75% of the relevant testing set.

/pdf/evolution-and-impact-of-bias-in-human-and-machine-learning-4s7k77itlv.pdf

Evolution and impact of bias in human and machine learning algorithm interaction

The framework of multi-objective clustering can serve as a competent technique in nowadays human issues ranging from decision making process to machine learning and pattern recognition problems. Multi-objective clustering basically aims at placing similar objects into the same groups based on some conflicting objectives, which substantially supports the use of game theory to come to a resolution. Based on these understandings, this paper suggests Enriched Game Theory K-means, called EGTKMeans, as a novel multi-objective clustering technique based on the notion of game theory. EGTKMeans is specially designed to optimize two intrinsically conflicting objectives, named, compaction and equi-partitioning. The key contributions of the proposed approach are three folds. First, it formulates an elegant and novel payoff definition which considers both objectives with equal priority. The presented payoff function incorporates a desirable fairness into the final clustering results. Second, EGTKMeans performs better off by utilizing the advantages of mixed strategies as well as those of pure ones, considering the existence of mixed Nash Equilibrium in every game. The last but not the least is that EGTKMeans approaches the optimal solution in a very promising manner by optimizing both objectives simultaneously. The experimental results suggest that the proposed approach significantly outperforms other rival methods across real world and synthetic data sets with reasonable time complexity.

An enriched game-theoretic framework for multi-objective clustering

Social networks, along with their “event” organization, planning, and sharing tools, play an important role in connecting and engaging individuals and groups. These online spaces thrive with multifaceted activities and interests which give rise to rich content and user interaction that often crossover to the world of events. For these reasons, the data trails associated with “events” in the virtual world can be complex and challenging to understand and predict. This paper presents our efforts to build an interpretable framework to analyze event data and recommend relevant events to social media users with different preferences. The datasets for this challenge were provided by a competition on Kaggle. We conduct an extensive data analysis and exploration to help gain a better understanding of the data. We then proceed to the critical phase of feature engineering, storytelling and modeling for computing event recommendations. We explore fuzzy approximate reasoning for modeling because of its rich linguistic expression ability which allows handling uncertainty, while maintaining human interpretability of the built models and predictions. This interpretability is critical in the data mining enterprise because data mining often requires team collaboration and yields results that need to be consumed by people of diverse technical and non-technical background. Such teams tend to question the meaning of models and emphasize the importance of telling stories from the data. We evaluate our event recommendation system on a real-world dataset with more than one million events and 38,000 users. The proposed methodology achieved 70% accuracy, outperforming existing event recommendation algorithms.

A case study for intelligent event recommendation

We describe the methodology that we followed to automatically extract topics corresponding to known events provided by the SNOW 2014 challenge in the context of the SocialSensor project. A data crawling tool and selected filtering terms were provided to all the teams. The crawled data was to be divided in 96 (15-minute) timeslots spanning a 24 hour period and participants were asked to produce a fixed number of topics for the selected timeslots. Our preliminary results are obtained using a methodology that pulls strengths from several machine learning techniques, including Latent Dirichlet Allocation (LDA) for topic modeling and Non-negative Matrix Factorization (NMF) for automated hashtag annotation and for mapping the topics into a latent space where they become less fragmented and can be better related with one another. In addition, we obtain improved topic quality when Copyright c © by the paper’s authors. Copying permitted only for private and academic purposes. In: S. Papadopoulos, D. Corney, L. Aiello (eds.): Proceedings of the SNOW 2014 Data Challenge, Seoul, Korea, 08-04-2014, published at http://ceur-ws.org sentiment detection is performed to partition the tweets based on polarity, prior to topic modeling.

Distributed LDA-based Topic Modeling and Topic Agglomeration in a Latent Space.

Real-time micro-blogging services such as Twitter generate billions of micro-posts to share information, daily. However, these posts are inherently noisy and unstructured, hence making them difficult to organize for the purpose of retrieval of relevant information.Hashtags are quickly becoming the standard approach for annotation of various information on social media. However hashtags are not used in a consistent manner and most importantly, are completely optional to use. This makes them unreliable as the sole mechanism for searching for relevant information. In this paper, we investigate mechanisms for consolidating the hashtag space using recom-mender systems. We propose a cross-domain collaborative filtering recommender system based on matrix factorization (MF) combined with a hashtag similarity graph, to automatically predict relevant hashtags based on an analysis of existing data and the relations among hashtags. Our experiments confirm that our approach outperforms several baselines. Our research using these hashtag graphs for recommendations has further revealed a promising mechanism for revealing stories from the cliques in this graph, paving the road toward story annotation as an extension of hashtag recommendation for tweets.

Cross-Domain Hashtag Recommendation and Story Revelation in Social Media

PEEKING INTO THE OTHER HALF OF THE GLASS: HANDLING POLARIZATION IN RECOMMENDER SYSTEMS

https://ir.library.louisville.edu/cgi/viewcontent.cgi?article=3835&context=etd

Peeking into the other half of the glass : handling polarization in recommender systems.

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