Pantelis Pipergias Analytis visit

On October 9th, we are lucky to have Pantelis Pipergias Analytis visiting the group. Pantelis recently moved as an assistant professor at the Danish Institute of Advanced Studies (D-IAS) at the  University of Southern Denmark.

Before moving to Denmark, he spent the past two years as a postdoctoral researcher at the Computer and Information Science department at Cornell University. Pantelis got his PhD from the Max Planck Institute for Human Development in Berlin.

Pantelis will give a talk based on his recent Nature Human Behavior paper Social learning strategies for matters of taste

  • Date: October 9th
  • Time: 13:30
  • Place: Technical University of Denmark, Building 321, Room 134

TitleSocial learning strategies for matters of taste

Abstract: Most choices people make are about ‘matters of taste’, on which there is no universal, objective truth. Nevertheless, people can learn from the experiences of individuals with similar tastes who have already evaluated the available options—a poten- tial harnessed by recommender systems. We mapped recommender system algorithms to models of human judgement and decision-making about ‘matters of fact’ and recast the latter as social learning strategies for matters of taste. Using computer simulations on a large-scale, empirical dataset, we studied how people could leverage the experiences of others to make better decisions. Our simulations showed that experienced individuals can benefit from relying mostly on the opinions of seemingly similar people; by contrast, inexperienced individuals cannot reliably estimate similarity and are better off picking the main- stream option despite differences in taste. Crucially, the level of experience beyond which people should switch to similarity- heavy strategies varies substantially across individuals and depends on how mainstream (or alternative) an individual’s tastes are and the level of dispersion in taste similarity with the other people in the group.

Piotr Sapieżyński on Fairness in ranking

Our old friend Piotr, current postdoc at Northeastern, and graduate from the group is visiting from his new home beyond the Atlantic. This coming Thursday, Piotr will give a short about his most recent work. Details below.

  • Time: Thursday, Sept 6th. 11AM
  • Location: Technical University of Denmark.B321, lab-space
  • Title: Fairness in ranking

Abstract: Ranked lists of persons and items are a core part of the user experience in many online services, such as search, social media feeds, hiring, and dating sites. Studies have shown disparate amount of attention received by high rank results, potentially leading to loss of opportunity and access to resources among the lower ranked items. In this short talk I will give an overview of the work on individual and group fairness in ranked lists and focus on our work in progress: a novel metric for investigating group unfairness in ranked lists. Our approach relies on estimating the amount of attention given to members of a protected group and comparing it to that group’s representation in a defined population. It offers two major developments compared to the state of the art. First, rather than assuming a logarithmic loss in importance as a function of the rank, we allow for attention distributions that are specific to the audited service and the habits of its users. For example, more items are consumed in a single viewing of a social media feed than as a result of a single query in a web search engine. Second, we allow non-binary protected attributes (gender, race, etc.), both to better reflect the way individuals identify, but also to enable measurements on aggregates of multiple search runs, rather than separately for each result list.We investigate the properties of the metric and compare them to the behavior of other established approaches using synthetic ranked lists. Finally, we showcase the metric through a simulated audit of a number of hiring and dating services.