About

Charles L Ortiz is a Professor in the Ecology & Evolutionary Biology Department within the Physical & Biological Sciences Division at UC Santa Cruz. His office is located in the Physical Sciences Building, 415, and he can be reached via phone at 831-459-2247 or 831-462-1357, and email at clortiz@ucsc.edu or ortiz@biology.ucsc.edu. His academic and research focus is within the field of Ecology & Evolutionary Biology, contributing to the department's mission of advancing understanding in these areas. Further details about his specific research interests, background, and key contributions are not provided on the page.

Research topics

• Medicine
• Zoology
• Internal medicine
• Physiology
• Endocrinology
• Biology

Selected publications

• Explaining Decisions of Agents in Mixed-Motive Games

  Proceedings of the AAAI Conference on Artificial Intelligence · 2025-04-11

  articleOpen access

  In recent years, agents have become capable of communicating seamlessly via natural language and navigating in environments that involve cooperation and competition, a fact that can introduce social dilemmas. Due to the interleaving of cooperation and competition, understanding agents' decision-making in such environments is challenging, and humans can benefit from obtaining explanations. However, such environments and scenarios have rarely been explored in the context of explainable AI. While some explanation methods for cooperative environments can be applied in mixed-motive setups, they do not address inter-agent competition, cheap-talk, or implicit communication by actions. In this work, we design explanation methods to address these issues. Then, we proceed to establish generality and demonstrate the applicability of the methods to three games with vastly different properties. Lastly, we demonstrate the effectiveness and usefulness of the methods for humans in two mixed-motive games. The first is a challenging 7-player game called no-press Diplomacy. The second is a 3-player game inspired by the prisoner's dilemma, featuring communication in natural language.

  PublisherOA PDFDOI

• Explaining Decisions of Agents in Mixed-Motive Games

  arXiv (Cornell University) · 2024-07-21

  preprintOpen access

  In recent years, agents have become capable of communicating seamlessly via natural language and navigating in environments that involve cooperation and competition, a fact that can introduce social dilemmas. Due to the interleaving of cooperation and competition, understanding agents' decision-making in such environments is challenging, and humans can benefit from obtaining explanations. However, such environments and scenarios have rarely been explored in the context of explainable AI. While some explanation methods for cooperative environments can be applied in mixed-motive setups, they do not address inter-agent competition, cheap-talk, or implicit communication by actions. In this work, we design explanation methods to address these issues. Then, we proceed to establish generality and demonstrate the applicability of the methods to three games with vastly different properties. Lastly, we demonstrate the effectiveness and usefulness of the methods for humans in two mixed-motive games. The first is a challenging 7-player game called no-press Diplomacy. The second is a 3-player game inspired by the prisoner's dilemma, featuring communication in natural language.

  PublisherOA PDFDOI

• Melatonin, an ancient ally against pancreatic disorders

  Melatonin Research · 2024

  • Medicine
  • Internal medicine

  Melatonin is mainly produced in the pineal gland of mammals with a circadian rhythm. It has also been synthesized in different organs and tissues including the gastrointestinal tract. Additionally, melatonin is widely present in plants and foodstuff. In addition to its effects on the sleep-wake cycle and reproductive regulation in photoperiodic animals, melatonin regulates a wide variety of cellular processes, participating in the control of antioxidant defenses, immune response, energy metabolism, cell growth and proliferation, having beneficial effects on most of the tissues and organs, including the pancreas. Here, we have reviewed the recent findings related to the effects of melatonin on the physiology of the exocrine pancreas. Of major relevance, the effects of the indoleamine on pathological processes such as cancer, inflammation, diabetes, and fibrosis are also reviewed. Not less important, its effects on normal/healthy cells of the pancreas to modulate normal physiological functions are discussed.

  DOI

• Hormones and Fuel Regulation in Fasting Elephant Seals

  University of California Press eBooks · 2023 · 2 citations

  Senior authorCorresponding
  • Zoology
  • Biology
  • Physiology
  PublisherDOI

• Unpacking Human Teachers’ Intentions for Natural Interactive Task Learning

  2021-08-08 · 1 citations

  preprintOpen access

  Interactive Task Learning (ITL) is an emerging research agenda that studies the design of complex intelligent robots that can acquire new knowledge through natural human teacher-robot learner interactions. ITL methods are particularly useful for designing intelligent robots whose behavior can be adapted by humans collaborating with them. Various research communities are contributing methods for ITL and a large subset of this research is robot-centered with a focus on developing algorithms that can learn online, quickly. This paper studies the ITL problem from a human-centered perspective to provide guidance for robot design so that human teachers can naturally teach ITL robots. In this paper, we present 1) a qualitative bidirectional analysis of an interactive teaching study (N=10) through which we characterize various aspects of actions intended and executed by human teachers when teaching a robot; 2) an in-depth discussion of the teaching approach employed by two participants to understand the need for personal adaptation to individual teaching styles; and 3) requirements for ITL robot design based on our analyses and informed by a computational theory of collaborative interactions, SharedPlans.

  PublisherOA PDFDOI

• Holistic Conversational Assistants

  AI Magazine · 2018-03-01 · 6 citations

  articleOpen access1st authorCorresponding

  This column describes work being done at Nuance Communications in developing virtual personal assistants (VPAs) that can engage in extended task‐centered dialogues and that involve the coordination of many complex modules, along with conversational and collaborative support to such VPAs.

  PublisherOA PDFDOI

• The First Winograd Schema Challenge at IJCAI‐16

  AI Magazine · 2017-09-01 · 31 citations

  articleOpen accessSenior author

  The first Winograd Schema Challenge was held in New York, New York, as part of the International Joint Conference on Artificial Intelligence. The challenge was original conceived by Hector Levesque as an alternative to the Turing test. This report details the results of this first challenge.

  PublisherOA PDFDOI

• Why We Need a Physically Embodied Turing Test and What It Might Look Like

  AI Magazine · 2016-03-01 · 66 citations

  articleOpen access1st authorCorresponding

  The Turing test, as originally conceived, focused on language and reasoning; problems of perception and action were conspicuously absent. To serve as a benchmark for motivating and monitoring progress in AI research, this article proposes an extension to that original proposal that incorporates all four of these aspects of intelligence. Some initial suggestions are made regarding how best to structure such a test and how to measure progress. The proposed test also provides an opportunity to bring these four important areas of AI research back into sync after each has regrettably diverged into a fairly independent area of research of its own.

  PublisherOA PDFDOI

• Planning, Executing, and Evaluating the Winograd Schema Challenge

  AI Magazine · 2016-03-01 · 57 citations

  articleOpen accessSenior author

  The Winograd Schema Challenge (WSC) was proposed by Hector Levesque in 2011 as an alternative to the Turing test. Chief among its features is a simple question format that can span many commonsense knowledge domains. Questions are chosen so that they do not require specialized knoweldge or training and are easy for humans to answer. This article details our plans to run the WSC and evaluate results.

  PublisherOA PDFDOI

• The Winograd Schema Challenge: Evaluating Progress in Commonsense Reasoning

  Proceedings of the AAAI Conference on Artificial Intelligence · 2015-01-25 · 22 citations

  articleOpen accessSenior author

  This paper describes the Winograd Schema Challenge (WSC), which has been suggested as an alternative to the Turing Test and as a means of measuring progress in commonsense reasoning. A competition based on the WSC has been organized and announced to the AI research community. The WSC is of special interest to the AI applications community and we encourage its members to participate.

  PublisherDOI

Recent grants

• University of California, Santa Cruz IMSD Program

  NIH · $20.2M · 1999–2021

• NIH Grant S06GM008132

  NIH · $3.1M · 1999

• UCSC-MARC U*STAR Program

  NIH · $9.8M · 1980–2022

Frequent coauthors

• Rudy M. Ortiz

  University of California, Merced

  18 shared

• Sarit Kraus

  11 shared

• Osher Yadgar

  SRI International

  8 shared

• Régis Vincent

  Schlumberger (British Virgin Islands)

  8 shared

• Charles E. Wade

  The University of Texas Health Science Center at Houston

  8 shared

• Daniel P. Costa

  Brazilian Agricultural Research Corporation

  7 shared

• Eric Hsu

  University of Toronto

  6 shared

• Benoit Morisset

  5 shared