Question: Michael C. Frank, a developmental psychologist at Stanford University, studied which indigenous language of the Amazonas in Brazil?

Context paragraphs:
John C. Mitchell: John C. Mitchell is the Vice Provost for Teaching and Learning at Stanford University, the Mary and Gordon Crary Family Professor in Computer Science and Electrical Engineering at Stanford University, co-director of the Stanford Computer Security Lab, and Professor (by courtesy) of Education.  He is a member of the steering committee for Stanford University's Cyber Initiative.  Mitchell has been Vice Provost at Stanford University since 2012, first as the inaugural Vice Provost for Online Learning and now in a broader role for Teaching and Learning.  Under Mitchell's direction, the Office of the Vice Provost for Teaching and Learning (VPTL) is advancing teaching and learning through faculty-driven initiatives and research, transforming education in Stanford's classrooms and beyond.

Pirahã language: Pirahã (also spelled "Pirahá, Pirahán"), or Múra-Pirahã, is the indigenous language of the isolated Pirahã of Amazonas, Brazil.  The Pirahã live along the Maici River, a tributary of the Amazon River.

Hasso Plattner Institute of Design: The Hasso Plattner Institute of Design at Stanford, commonly known as the d.school, is a design thinking institute based in Stanford University.  Bernard Roth, co-founder of the Stanford d.school describes "Self-Image By Design" thus, "In the Stanford d.school we attempt to bring students through a series of experiences that change their self-image so that they think of themselves as being more creative.  We call this boosting their "creative confidence".  Michael C. Jensen, Werner Erhard, and their associates use a similar concept in leadership training; they call it 'changing the context'.  Others call these types of changes 'reframing' or 'changing frameworks'.  Whatever it is called, the psychological milieu in which we operate is important because it acts as a hidden arbitrator in how we approach many aspects of our lives."  According to the "New York Times", the school has become one of the most highly sought destinations at Stanford.

Amazonas State University: The Amazonas State University (Portuguese: "Universidade do Estado do Amazonas" , UEA) is a Brazilian public university operated by the state of Amazonas, located in Manaus, Amazonas, Brazil.  It was established in 2001 by a state law that turned the University of Technology of Amazonas (Universidade de Tecnologia do Amazonas) into the UEA.  In 2011 UEA was ranked the best university of the state in an evaluation made by the Ministry of Education.

David R. Olson: David Richard Olson (born June 16, 1935) is a Canadian cognitive developmental psychologist who has studied the development of language, literacy, and cognition, particularly the mental lives of children, their understanding of language and mind and the psychology of teaching.  Olson is University Professor Emeritus at the Ontario Institute for Studies in Education at the University of Toronto, where he has taught since 1966.

Arnold J. Sameroff: Arnold J. Sameroff is an American developmental psychologist.  He researches and writes about developmental theory and the factors that contribute to mental health and psychopathology, especially related to risk and resilience.  Together with Michael Chandler he is known for developing the transactional model of development.  He is one of the founders of the field of developmental psychopathology.

John H. Flavell: John H. Flavell (born August 9, 1928 in Rockland, Massachusetts) is an American developmental psychologist specializing in children's cognitive development.  After serving in The United States Army for two years from 1945–1947, John H. Flavell enrolled at Northeastern University where he earned his bachelor's degree in psychology.  After graduation, he was admitted into the clinical psychology program at Clark University and Harvard University.  John H. Flavell earned his MA from Clark University in 1952 and in 1955 he earned his Ph.D.  Through the discovery of new developmental phenomena and analysis of the theories of Jean Piaget, Flavell shifted the direction of developmental psychology in the United States.

Apurinã language: Apurinã (Ipurina) is a Southern Maipurean language spoken by the Apurinã people of the Amazon basin.  It has an active–stative syntax.  Apurinã is a Portuguese word used to describe the Popikariwakori people and the language they speak (Facundes 34, 2000).  Apurinã indigenous communities are predominantly found along the Purus river in the Northwestern Amazon region in Brazil, in the Amazonas state (Pickering 2, 2009).  Its population is currently spread over twenty-seven different indigenous lands along the Purus river (Apurinã PIB).  with an estimated population of 9,500 people in total.  It is predicted however that less than 30% of the Apurinã population is able to speak the language fluently (Facundes 35, 2000).  A definite number of speakers cannot be firmly determined due to a regional scattered presence of its people.  The spread of Apurinã speakers to different regions was due initially to conflict or disease, which consequently led natives to lose the ability to speak the language due to lack of practice and interactions with other communities.  Secondly, as a consequence of violence and oppression towards indigenous people, some natives and descendants choose to not identify themselves as indigenous further reducing the number of people that are categorized as speaking the language (Facundes 23, 2000).  The consequence of this low transmission and cultivation of the language results is the risk of endangerment.  The endangerment level of Apurinã is currently at level 3 (Facundes 4, 2000), meaning that although adults still speak the language, children are no longer being exposed to it and are being taught Portuguese or Spanish instead.  This could consequently lead to a further reduction in the number of people that speak the language over the years and eventually lead it go become extinct.

Federal University of Amazonas: The Federal University of Amazonas (Portuguese: "Universidade Federal do Amazonas" , UFAM) is a public university located in Manaus, state of Amazonas, Brazil.  It is the oldest university in Brazil and the largest university in the northern region of Brazil.  It offers a wide array of degrees, with 645 research groups and 65 graduate courses.

Michael C. Frank: Michael C. Frank is a developmental psychologist at Stanford University who proposed that infants' language development may be thought of as a process of Bayesian inference.  He has also studied the role of language in numerical cognition by comparing the performance of native Pirahã language speakers to that of MIT undergraduate students in numeric tasks.  For this work, he traveled to Amazonas, Brazil with Daniel Everett, a linguist best known for his claim that Pirahã disproves a crucial component of Noam Chomsky's theory of universal grammar, recursion.  Frank won the Cognitive Science Society's prestigious Marr Award for this work in 2008.

Supporting paragraphs: Michael C. Frank Pirahã language
Answer: Pirahã language