abstract: Researchers have documented the importance of seeing a graph as an emergent trace of how two quantities’ values vary simultaneously in order to reason about the graph in terms of quantitative relationships. If a student does not see a graph as a representation of how quantities change together then the student is limited to reasoning about perceptual features of the shape of the graph. This dissertation reports results of an investigation into the ways of thinking that support and inhibit students from constructing and reasoning about graphs in terms of covarying quantities. I collected data by engaging three university precalculus students in asynchronous teaching experiments. I designed the instructional sequence to support students in making three constructions: first imagine representing quantities’ magnitudes along the axes, then simultaneously represent these magnitudes with a correspondence point in the plane, and finally anticipate tracking the correspondence point to track how the two quantities’ attributes change simultaneously. Findings from this investigation provide insights into how students come to engage in covariational reasoning and re-present their imagery in their graphing actions. The data presented here suggests that it is nontrivial for students to coordinate their images of two varying quantities. This is significant because without a way to coordinate two quantities’ variation the student is limited to engaging in static shape thinking. I describe three types of imagery: a correspondence point, Tinker Bell and her pixie dust, and an actor taking baby steps, that supported students in developing ways to coordinate quantities’ variation. I discuss the figurative aspects of the students’ coordination in order to account for the difficulties students had (1) constructing a multiplicative object that persisted under variation, (2) reconstructing their acts of covariation in other graphing tasks, and (3) generalizing these acts of covariation to reason about formulas in terms of covarying quantities. / Dissertation/Thesis / Doctoral Dissertation Mathematics 2017

Quantitative reasoning permeates mathematical thinking, and mathematics education researchers have taken a quantitative reasoning approach to examining and modeling students' mathematical thinking and development in various domains. From this approach, secondary and post-secondary researchers have focused on students' ability to reason about how two quantities vary together (covariational reasoning). However, little is known about how covariational reasoning develops from, or connects with, arithmetic and algebraic reasoning. This study begins to bridge the gap in this knowledge. Originally this study was designed to examine middle grade students' units coordination in covariational reasoning across stages and consider the cognitive limiting factor of working memory. In this case study of Daniel, an advanced Stage 2 middle-grade algebra student, I examined the role his units coordinating structures played in his covariational reasoning in non-graphing and algebra tasks. I considered three main components in covariational reasoning (type of quantity, modality of change, and role of time) when analyzing covariational reasoning and capturing the underlying mental units and actions. I found type of quantity and time were the two biggest factors when determining Daniel's covariational reasoning. Daniel also used his units coordinating structures in various ways in the different covariation tasks, generating three different types of change units that were cognitively structurally different. These findings suggest cognitive connections between the types of units a student assimilates with, and the types of covariational reasoning they engage in, are interconnected and warrant future study. / Doctor of Philosophy / This study examines connections between middle-grade students' arithmetic reasoning and algebraic reasoning in their conceptualization of how two quantities vary together (covariation). I interviewed 6 cognitively diverse middle-grade students to investigate these connections and determine at the level of mental action level the types of quantities and actions students use in covariation. After collecting data on the 6 students and reflecting on the richness of each case, I elected to focus on one student for a fine-grain analysis. From this case study of Daniel, an algebra student, I found he used his arithmetic unit structures in unique ways depending on what quantities a task asked him to work with. I also found that Daniel's use of time as a measured quantity in his covariational reasoning influenced how he conceptualized two quantities changing together.

abstract: This dissertation describes an investigation of four students' ways of thinking about functions of two variables and rate of change of those two-variable functions. Most secondary, introductory algebra, pre-calculus, and first and second semester calculus courses do not require students to think about functions of more than one variable. Yet vector calculus, calculus on manifolds, linear algebra, and differential equations all rest upon the idea of functions of two (or more) variables. This dissertation contributes to understanding productive ways of thinking that can support students in thinking about functions of two or more variables as they describe complex systems with multiple variables interacting. This dissertation focuses on modeling the way of thinking of four students who participated in a specific instructional sequence designed to explore the limits of their ways of thinking and in turn, develop a robust model that could explain, describe, and predict students' actions relative to specific tasks. The data was collected using a teaching experiment methodology, and the tasks within the teaching experiment leveraged quantitative reasoning and covariation as foundations of students developing a coherent understanding of two-variable functions and their rates of change. The findings of this study indicated that I could characterize students' ways of thinking about two-variable functions by focusing on their use of novice and/or expert shape thinking, and the students' ways of thinking about rate of change by focusing on their quantitative reasoning. The findings suggested that quantitative and covariational reasoning were foundational to a student's ability to generalize their understanding of a single-variable function to two or more variables, and their conception of rate of change to rate of change at a point in space. These results created a need to better understand how experts in the field, such as mathematicians and mathematics educators, thinking about multivariable functions and their rates of change. / Dissertation/Thesis / Ph.D. Mathematics 2012

Mathematics education reform has led to more conceptually focused instruction in the classroom. Yet, students with disabilities are receiving fewer chances than other students to engage in meaningful mathematics. Furthermore, a research divide between mathematics education and special education in mathematics has led to significant gaps in research on the individual and conceptual understanding of students with disabilities. Through task-based interviews and classroom observations, this study begins the process of closing this research gap through an examination of students' understanding of variational and covariational reasoning. Data suggest that the participants, two students with disabilities, increased their conceptual understanding in a reformed learning environment with support from teacher presence and questions. The students were able to increase their understanding of the difference between discrete and continuous functions, demonstrated an ability to self-correct, and improved their ability to choose appropriate levels of reasoning. The results suggest that conceptually oriented instruction with the presence and questioning of a teacher can support students with disabilities in developing a deep and rich understanding of complex mathematics.

Afin de mieux cerner les enjeux de la transition entre le secondaire et le postsecondaire, nous proposons un examen du passage de la notion de fonction à celle de dérivée. À la lumière de plusieurs travaux mettant en évidence des difficultés inhérentes à ce passage, et nous basant sur les recherches de Carlson et ses collègues (Carlson, 2002; Carlson, Jacobs, Coe, Larsen et Hsu, 2002; Carlson, Larsen et Jacobs, 2001; Oehrtman, Carlson et Thompson, 2008) sur le raisonnement covariationnel, nous présentons une analyse de la dynamique du développement de ce raisonnement chez des petits groupes d’élèves de la fin du secondaire et du début du collégial dans quatre situations-problèmes différentes. L’analyse des raisonnements de ces groupes d’élèves nous a permis, d’une part, de raffiner la grille proposée par Carlson en mettant en évidence, non seulement des unités de processus de modélisation (ou unités de raisonnement) mises en action par ces élèves lors des activités proposées, mais aussi leurs rôles au sein de la dynamique du raisonnement. D’autre part, cette analyse révèle l’influence de certaines caractéristiques des situations sur les interactions non linéaires entre ces unités. / To better understand the transitional challenges between high-school and post-secondary education, we propose a study of the passage from the notion of function to the notion of derivative. Based on numerous studies on the difficulties related to this passage and, more specifically, on the work of Carlson and colleague’s (Carlson, 2002; Carlson, Jacobs, Coe, Larsen & Hsu, 2002; Carlson, Larsen & Jacobs, 2001; Oehrtman, Carlson & Thompson, 2008) on covariational reasoning, we present an analysis of the dynamics of the development of covariational reasoning. By submitting four different problem-situations to small groups of students ending secondary school and beginning college (15-18 years old), we were able to examine that development. On one hand, the analysis of the reasoning of those students allowed us to refine the grid proposed by Carlson, bringing out, not only the reasoning units used by those students during the proposed activities, but also their role in the dynamic of the reasoning. On the other hand, this analysis reveals the influence of certain characteristics of the situations on the non-linear interactions between those units.

A ausência do Cálculo Diferencial e Integral no currículo do Ensino Médio no Brasil, diferentemente do que acontece em outros países, constituiu-se na motivação original para este trabalho. Considerando as finalidades mais gerais da escola básica apresentadas nos documentos oficiais, mostramos o aporte que o ensino de Cálculo pode conduzir à formação de nossos jovens, favorecendo uma visão mais integrada das disciplinas e o desenvolvimento da capacidade de compreender e interpretar fenômenos. Trazer o estudo do Cálculo para a escola básica, porém, não pode significar uma antecipação do que é feito nos cursos universitários, como acontecia no Brasil há algumas décadas. Pelo contrário, a abordagem deve se basear nas ideias fundamentais do Cálculo, como variação, aproximação e proporcionalidade, que já estão presentes no programa da escola básica. Para tanto, apresentamos o raciocínio covariacional, definido como o conjunto de atividades cognitivas envolvidas na análise coordenada das variações de duas grandezas interdependentes. Construindo uma trajetória que começa nas séries iniciais, chega às grandezas proporcionais, perpassa todo o estudo das funções e se estende até o final do Ensino Médio, mostramos que o modelo representado pelo raciocínio covariacional pode nortear o processo de fortalecimento das ideias do Cálculo no currículo da escola básica. Para ter uma noção do cenário atual, avaliamos o nível de raciocínio covariacional de 66 alunos recém-formados no Ensino Médio brasileiro, aprovados em um competitivo exame seletivo para ingresso na universidade. A enorme dispersão dos resultados indicou a pouca consistência do atual programa de nossa escola básica em relação ao desenvolvimento do raciocínio covariacional. Aproveitando o estudo realizado, extrapolamos o contexto da escola básica para avaliar a relação entre o nível inicial de raciocínio covariacional dos alunos e seu desempenho na disciplina de Cálculo na universidade. Os resultados sinalizam para o efeito positivo que um trabalho mais efetivo com o raciocínio covariacional pode ter no enfrentamento das dificuldades vividas por alunos e professores nas disciplinas de Cálculo do ensino superior. / The absence of Differential and Integral Calculus in Brazilian high school syllabus, differently from what happens in other countries, has been the main motivation to develop this thesis. Considering the most general objectives of the K-12 education presented in the official documents, we hereby demonstrate the robust contribution of teaching Calculus to the secondary school students, by offering an integrated discipline overview, and the development of the ability of understanding and interpreting phenomena. However, the introduction of the study of Calculus to secondary school should not be an anticipation of what is developed in the university courses, as it used to be some decades ago in Brazil. The approach, on the other hand, should be based on the Calculus fundamental ideas, such as: variation, approximation and proportionality, which are already present in the K-12 curriculum. Therefore, we described the covariational reasoning, which is defined as the cognitive activities involved in the coordinated analysis of two interdependent quantities variations. We have designed a track using a covariation framework, starting in elementary school, which then achieves the study of proportionality and functions, and extends up to the end of high school, resulting in the strengthening of the Calculus ideas in the curriculum. In order to have a general view of the current scenario, we evaluated the covariational reasoning level of 66 recent graduated high school students in Brazil, who were approved in a high competitive exam in order to enter university. As a result, we detected an impressive lack of consistency regarding the development of covariational reasoning in the secondary school curriculum. Moreover, we could evaluate the relation between the initial students covariational reasoning level and their understanding of Calculus in the university. Our results indicate that fostering covariational reasoning may effectively lead to a positive influence, when dealing with difficulties faced by students and faculty in Calculus courses at the university level.

A ausência do Cálculo Diferencial e Integral no currículo do Ensino Médio no Brasil, diferentemente do que acontece em outros países, constituiu-se na motivação original para este trabalho. Considerando as finalidades mais gerais da escola básica apresentadas nos documentos oficiais, mostramos o aporte que o ensino de Cálculo pode conduzir à formação de nossos jovens, favorecendo uma visão mais integrada das disciplinas e o desenvolvimento da capacidade de compreender e interpretar fenômenos. Trazer o estudo do Cálculo para a escola básica, porém, não pode significar uma antecipação do que é feito nos cursos universitários, como acontecia no Brasil há algumas décadas. Pelo contrário, a abordagem deve se basear nas ideias fundamentais do Cálculo, como variação, aproximação e proporcionalidade, que já estão presentes no programa da escola básica. Para tanto, apresentamos o raciocínio covariacional, definido como o conjunto de atividades cognitivas envolvidas na análise coordenada das variações de duas grandezas interdependentes. Construindo uma trajetória que começa nas séries iniciais, chega às grandezas proporcionais, perpassa todo o estudo das funções e se estende até o final do Ensino Médio, mostramos que o modelo representado pelo raciocínio covariacional pode nortear o processo de fortalecimento das ideias do Cálculo no currículo da escola básica. Para ter uma noção do cenário atual, avaliamos o nível de raciocínio covariacional de 66 alunos recém-formados no Ensino Médio brasileiro, aprovados em um competitivo exame seletivo para ingresso na universidade. A enorme dispersão dos resultados indicou a pouca consistência do atual programa de nossa escola básica em relação ao desenvolvimento do raciocínio covariacional. Aproveitando o estudo realizado, extrapolamos o contexto da escola básica para avaliar a relação entre o nível inicial de raciocínio covariacional dos alunos e seu desempenho na disciplina de Cálculo na universidade. Os resultados sinalizam para o efeito positivo que um trabalho mais efetivo com o raciocínio covariacional pode ter no enfrentamento das dificuldades vividas por alunos e professores nas disciplinas de Cálculo do ensino superior. / The absence of Differential and Integral Calculus in Brazilian high school syllabus, differently from what happens in other countries, has been the main motivation to develop this thesis. Considering the most general objectives of the K-12 education presented in the official documents, we hereby demonstrate the robust contribution of teaching Calculus to the secondary school students, by offering an integrated discipline overview, and the development of the ability of understanding and interpreting phenomena. However, the introduction of the study of Calculus to secondary school should not be an anticipation of what is developed in the university courses, as it used to be some decades ago in Brazil. The approach, on the other hand, should be based on the Calculus fundamental ideas, such as: variation, approximation and proportionality, which are already present in the K-12 curriculum. Therefore, we described the covariational reasoning, which is defined as the cognitive activities involved in the coordinated analysis of two interdependent quantities variations. We have designed a track using a covariation framework, starting in elementary school, which then achieves the study of proportionality and functions, and extends up to the end of high school, resulting in the strengthening of the Calculus ideas in the curriculum. In order to have a general view of the current scenario, we evaluated the covariational reasoning level of 66 recent graduated high school students in Brazil, who were approved in a high competitive exam in order to enter university. As a result, we detected an impressive lack of consistency regarding the development of covariational reasoning in the secondary school curriculum. Moreover, we could evaluate the relation between the initial students covariational reasoning level and their understanding of Calculus in the university. Our results indicate that fostering covariational reasoning may effectively lead to a positive influence, when dealing with difficulties faced by students and faculty in Calculus courses at the university level.