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Recsperts - Recommender Systems Experts

Recsperts - Recommender Systems Experts

Auteur(s): Marcel Kurovski
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 Recommender Systems are the most challenging, powerful and ubiquitous area of machine learning and artificial intelligence. This podcast hosts the experts in recommender systems research and application. From understanding what users really want to driving large-scale content discovery - from delivering personalized online experiences to catering to multi-stakeholder goals. Guests from industry and academia share how they tackle these and many more challenges. With Recsperts coming from universities all around the globe or from various industries like streaming, ecommerce, news, or social media, this podcast provides depth and insights. We go far beyond your 101 on RecSys and the shallowness of another matrix factorization based rating prediction blogpost! The motto is: be relevant or become irrelevant! Expect a brand-new interview each month and follow Recsperts on your favorite podcast player.© 2026 Marcel Kurovski Mathématique Science
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  • #31: Psychology-Aware Recommender Systems with Elisabeth Lex

    #31: Psychology-Aware Recommender Systems with Elisabeth Lex
    Feb 19 2026
    In episode 31 of Recsperts, I sit down with Elisabeth Lex, Full Professor of Human-Computer Interfaces and Inclusive Technologies at Graz University of Technology and a leading researcher at the intersection of recommender systems, psychology, and human–computer interaction. Together, we explore how recommender systems can become truly human-centric by integrating cognitive, emotional, and personality-aware models into their design.Elisabeth begins by addressing a common reductionism in the field: treating users primarily as data points rather than as humans with goals, emotions, memories, and cognitive boundaries. We revisit the origins of psychology-informed recommendation, including the Grundy system -the first recommender system, built nearly 50 years ago - which framed book recommendation through stereotype modeling. From there, we discuss how the community’s focus shifted toward solving recommendation mainly as an algorithmic optimization problem, often sidelining richer models of human decision-making.We then map out the three major branches of psychology-informed RecSys - cognition-inspired, affect-aware, and personality-aware - and dive into practical examples. Elisabeth walks us through her work on modeling music re-listening behavior using cognitive architectures such as ACT-R (Adaptive Control of Thought–Rational) and shows how cognitive constructs like memory decay, attention, and familiarity can meaningfully augment standard approaches like collaborative filtering. We also explore how hybrid systems that combine cognitive models with collaborative filtering can yield not just higher accuracy but also more novelty, diversity, and clearer explanations.Our conversation also turns to user-centric evaluation. Elisabeth argues that accuracy metrics alone cannot tell us whether a system is genuinely helpful. Instead, we must measure attitudes, perceptions, motivations, and emotional responses - while carefully accounting for cognitive biases, UI effects, and users’ lived experiences.Towards the end, Elisabeth discusses emerging research directions such as hybrid AI (symbolic + sub-symbolic methods), the role of LLMs and agents, the risks of replacing human studies with automated evaluations, and the responsibility our community has to understand users beyond their clicks.Enjoy this enriching episode of RECSPERTS – Recommender Systems Experts.Don’t forget to follow the podcast and please leave a review.(00:00) - Introduction(03:15) - About Elisabeth Lex(07:55) - Grundy, the first Recommender System (09:03) - Bridging the Gap between Psychology and Modern RecSys(17:21) - On how and when Elisabeth became a Researcher(21:39) - Survey on Psychology-Informed RecSys(39:29) - Personality-Aware Recommendation(49:43) - Affect- and Emotion-Aware Recommendation(01:01:37) - Cognition-Inspired Recommendation and the ACT-R Framework(01:14:39) - Combining Collaborative Filtering and ACT-R for Explainability(01:21:26) - Human-Centered Design(01:26:15) - Further Challenges and Closing RemarksLinks from the Episode:Elisabeth Lex on LinkedInWebsite of ElisabethAI for Society LabFirst International Workshop on Recommender Systems for Sustainability and Social Good | co-located with RecSys 2024Second International Workshop on Recommender Systems for Sustainability and Social Good | co-located with RecSys 2025HyPer Workshop: Hybrid AI for Human-Centric PersonalizationTutorial on Psychology-Informed RecSysACT-R: Adaptive Control of Thought-RationalPOPROX: Platform for OPen Recommendation and Online eXperimentationPapers:Elaine Rich (1979): User Modeling via StereotypesLex et al. (2021): Psychology-informed Recommender SystemsReiter-Haas et al. (2021): Predicting Music Relistening Behavior Using the ACT-R FrameworkMoscati et al. (2023): Integrating the ACT-R Framework with Collaborative Filtering for Explainable Sequential Music RecommendationTran et al. (2024): Transformers Meet ACT-R: Repeat-Aware and Sequential Listening Session RecommendationGeneral Links:Follow me on LinkedInFollow me on XSend me your comments, questions and suggestions to marcel.kurovski@gmail.comRecsperts Website
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    1 h et 37 min
  • #30: Serendipity for Recommender Systems with Annelien Smets

    #30: Serendipity for Recommender Systems with Annelien Smets
    Jan 28 2026
    In episode 30 of Recsperts, I speak with Annelien Smets, Professor at Vrije Universiteit Brussel and Senior Researcher at imec-SMIT, about the value, perception, and practical design of serendipity in recommender systems. Annelien introduces her framework for understanding serendipity through intention, experience, and affordances, and explains the paradox of artificial serendipity - why it cannot be engineered, but only designed for.We start by unpacking the paradox of serendipity: while serendipity cannot be engineered or planned, systems and environments can be designed to increase the likelihood that serendipitous experiences occur. Annelien explains why randomness alone is not enough and why serendipity always emerges from an interplay between an unexpected encounter and a user’s ability to recognize its relevance and value.A central part of our discussion focuses on Annelien’s recent framework that distinguishes between intended, experienced, and afforded serendipity. We explore why organizations first need to clarify why they want serendipity - whether as an ideal, a common good, a mediator to achieve other goals (such as long-term retention or long-tail exposure), or even as a product feature in itself. From there, we dive into how users actually experience serendipity, drawing on qualitative interview research that identifies three core components: encounters must feel fortuitous, refreshing, and enriching. These components can manifest in different “flavors,” such as taste broadening, taste deepening, or rediscovering forgotten interests.We then move beyond algorithms to discuss affordances for serendipity - design principles that span content, user interfaces, and information access. Using examples from libraries, urban spaces, and digital platforms, Annelien shows why serendipity is a system-level property rather than a single metric or model tweak. We also discuss where serendipity can go wrong, including the Netflix “Surprise Me” feature, and why mismatched expectations can actually harm user experience.To close, we reflect on open research questions, from measuring different types of serendipity to understanding how content types, business models, and platform economics shape what is possible. Annelien also challenges a common myth: serendipity does not automatically burst filter bubbles—and should not be treated as a silver bullet.Enjoy this enriching episode of RECSPERTS – Recommender Systems Experts.Don’t forget to follow the podcast and please leave a review.(00:00) - Introduction(03:57) - About Annelien Smets(14:42) - Paradox and Definition of (Artificial) Serendipity(27:04) - Intended Serendipity(43:01) - Experienced Serendipity(01:01:18) - Afforded Serendipity(01:13:49) - Examples of Serendipity Going Wrong(01:17:40) - Framework for Serendipity(01:22:41) - Further Challenges and Closing RemarksLinks from the Episode:Annelien Smets on LinkedInWebsite of AnnelienLinkedIn Article by Annelien Smets (2025): Overcoming the Paradox of Artificial SerendipityThe Serendipity SocietySerendipity EnginePapers:Smets (2025): Intended, afforded, and experienced serendipity: overcoming the paradox of artificial serendipitySmets et al. (2022): Serendipity in Recommender Systems Beyond the Algorithm: A Feature Repository and Experimental DesignBinst et al. (2025): What Is Serendipity? An Interview Study to Conceptualize Experienced Serendipity in Recommender SystemsZiarani et al. (2021): Serendipity in Recommender Systems: A Systematic Literature ReviewChen et al. (2021): Values of User Exploration in Recommender SystemsSmets et al. (2025): Why Do Recommenders Recommend? Three Waves of Research Perspectives on Recommender SystemsSmets (2023): Designing for Serendipity, a Means or an End?General Links:Follow me on LinkedInFollow me on XSend me your comments, questions and suggestions to marcel.kurovski@gmail.comRecsperts Website
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    1 h et 32 min
  • #29: Transformers for Recommender Systems with Craig Macdonald and Sasha Petrov

    #29: Transformers for Recommender Systems with Craig Macdonald and Sasha Petrov
    Aug 27 2025
    In episode 29 of Recsperts, I welcome Craig Macdonald, Professor of Information Retrieval at the University of Glasgow, and Aleksandr “Sasha” Petrov, PhD researcher and former applied scientist at Amazon. Together, we dive deep into sequential recommender systems and the growing role of transformer models such as SASRec and BERT4Rec.Our conversation begins with their influential replicability study of BERT4Rec, which revealed inconsistencies in reported results and highlighted the importance of training objectives over architecture tweaks. From there, Craig and Sasha guide us through their award-winning research on making transformers for sequential recommendation with large corpora both more effective and more efficient. We discuss how recency sampling (RSS) reduces training times dramatically, and how gSASRec overcomes the problem of overconfidence in models trained with negative sampling. By generalizing the sigmoid function (gBCE), they were able to reconcile cross-entropy–based optimization results with negative sampling, matching the effectiveness of softmax approaches while keeping training scalable for large corpora.We also explore RecJPQ, their recent work on joint product quantization for item embeddings. This approach makes transformer-based sequential recommenders substantially faster at inference and far more memory-efficient for embeddings—while sometimes even improving effectiveness thanks to regularization effects. Towards the end, Craig and Sasha share their perspective on generative approaches like GPTRec, the promises and limits of large language models in recommendation, and what challenges remain for the future of sequential recommender systems.Enjoy this enriching episode of RECSPERTS – Recommender Systems Experts.Don’t forget to follow the podcast and please leave a review.(00:00) - Introduction(04:09) - About Craig Macdonald(04:46) - About Sasha Petrov(13:48) - Tutorial on Transformers for Sequential Recommendations(19:24) - SASRec vs. BERT4Rec(21:25) - Replicability Study of BERT4Rec for Sequential Recommendation(32:52) - Training Sequential RecSys using Recency Sampling(40:01) - gSASRec for Reducing Overconfidence by Negative Sampling(01:00:51) - RecJPQ: Training Large-Catalogue Sequential Recommenders(01:21:37) - Generative Sequential Recommendation with GPTRec(01:29:12) - Further Challenges and Closing RemarksLinks from the Episode:Craig Macdonald on LinkedInSasha Petrov on LinkedInSasha's WebsiteTutorial: Transformers for Sequential Recommendation (ECIR 2024)Tutorial Recording from ACM European Summer School in Bari (2024)Talk: Neural Recommender Systems (European Summer School in Information Retrieval 2024)Papers:Kang et al. (2018): Self-Attentive Sequential RecommendationSun et al. (2019): BERT4Rec: Sequential Recommendation with Bidirectional Encoder Representations from TransformerPetrov et al. (2022): A Systematic Review and Replicability Study of BERT4Rec for Sequential RecommendationPetrov et al. (2022): Effective and Efficient Training for Sequential Recommendation using Recency SamplingPetrov et al. (2024): RSS: Effective and Efficient Training for Sequential Recommendation Using Recency Sampling (extended version)Petrov et al. (2023): gSASRec: Reducing Overconfidence in Sequential Recommendation Trained with Negative SamplingPetrov et al. (2025): Improving Effectiveness by Reducing Overconfidence in Large Catalogue Sequential Recommendation with gBCE lossPetrov et al. (2024): RecJPQ: Training Large-Catalogue Sequential RecommendersPetrov et al. (2024): Efficient Inference of Sub-Item Id-based Sequential Recommendation Models with Millions of ItemsRajput et al. (2023): Recommender Systems with Generative RetrievalPetrov et al. (2023): Generative Sequential Recommendation with GPTRecPetrov et al. (2024): Aligning GPTRec with Beyond-Accuracy Goals with Reinforcement LearningGeneral Links:Follow me on LinkedInFollow me on XSend me your comments, questions and suggestions to marcel.kurovski@gmail.comRecsperts WebsiteDisclaimer:Craig holds concurrent appointments as a Professor of Information Retrieval at University of Glasgow and as an Amazon Scholar. This podcast describes work performed at the University of Glasgow and is not associated with Amazon.
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    1 h et 37 min
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