Ratio Mathematica Volume 39, 2020, pp. 111-136 111 Teaching as a decision-making model: strategies in mathematics from a practical requirement Viviana Ventre* Eva Ferrara Dentice Roberta Martino† Abstract The need in the current social context to adopt teaching methods that can stimulate students and lead them towards autonomy, awareness and independence in studying could conflict with the needs of students with specific learning disorders, especially in higher education, where self-learning and self-orientation are required. In this sense, the choice of effective teaching strategies becomes a decision-making problem and must, therefore, be addressed as such. This article discusses some mathematical models for choosing effective methods in mathematics education for students with specific learning disorders. It moves from the case study of a student with specific reading and writing disorders enrolled in the mathematical analysis course 1 of the degree course in architecture and describes the personalised teaching strategy created for him. Keywords: decision-making; inquiry model; social skills; personalised didactic strategy; Analytic Hierarchy Process. 2010 AMS subject classification: 91B06, 97D60.‡ *. Corresponding author: viviana.ventre@unicampania.it †. All the authors belong to the Department of Mathematics and Physics of the University of the Study of Campania “L. Vanvitelli”, viale A. Lincoln n.5, I-81100, Caserta (CE), Italy. ‡ Received on November 20th, 2020. Accepted on December 22th, 2020. Published on December 31st, 2020. doi: 10.23755/rm.v39i0.559. ISSN: 1592-7415. eISSN: 2282- 8214. ©Ventre et al. This paper is published under the CC-BY licence agreement. Viviana Ventre, Eva Ferrara Dentice, Roberta Martino 112 1 Introduction In recent years the institutions have increased their interest in a very worrying phenomenon that concerns Italy and generally speaking the countries in the Western world: the growth of 'disaffection' towards mathematics due to a traditional didactic approach to the subject (Piochi, 2008). Young people coming out of secondary schools often have the idea that mathematics consists of mechanical processes, seeing it as an arid and pre-packaged discipline whose understanding and description seem impersonal. The mathematics one learns at school is very often a set of basic notions, axioms and definitions given by the teacher and practically impossible to discuss, causing the view of a subject that is “already done” and immutable (Castelnuovo, 1963). The experience of mathematicians, on the other hand, is very different: mathematics is something extremely changeable whose results are the result of hard work, debate and controversy. So, axioms and definitions first presented in textbooks come into reality only at the end, when the whole structure of the problem is understood. Then, the following question arises: what is mathematics? Definitions such as “mathematics is the science of numbers and forms” accepted 200 years ago is now reductive and ineffective because mathematics has developed so rapidly and intensely that no definition can take into account all the multiple aspects (Baccaglini-Frank, Di Martino, Natalini, Rosolini, 2018 (A)). The list of applications of this discipline in daily life could be endless, and so could the list of motivations that could be given to pupils to convince them to study. About this matter it is really important the following statement: "No doubt, mathematical knowledge is crucial to produce and maintain the most important aspects of our present life. This does not imply that the majority of people should know mathematics." (Vinner, 2000). Mathematics can also cause terror in students (the phenomenon of “fear for mathematics” (Bartilomo and Favilli, 2005)) or a state of dissatisfaction with the common conception that “you have to be made for it” so much that even great professionals boast that they have never understood anything about mathematics. So, is it necessary to teach mathematics to everyone? The answer is simple: apart from the fact that having a basis in mathematics is a cultural question regardless of the future job, mathematics teaches to evaluate multiple aspects of a question, and provides knowledge and skills in order to consciously face a discussion defending one's own positions with responsibility and respect for the arguments of others (National Indications, 2007). The key role of mathematics education in the development of rational thinking and with it the responsibilities of mathematics teachers at all levels is therefore underlined. Already in 1958, the theme of the congress of the Belgian Teaching as a decision-making model: strategies in mathematics from a practical requirement 113 Mathematical Society was entitled “The human responsibility of the mathematics teacher” (Castelnuovo, 1963). The most effective way to bring students closer to mathematics is, therefore, the image of a “method for dealing with problems, a language, a box of tools that allows us to strengthen our intuition” (Baccaglini-Frank, Di Martino, Natalini, Rosolini, 2018 (A)). 2 Mathematical education: theories and models 2.1 The concept of error and the inquiry model: mathematics as a humanistic discipline Mathematics is one of the disciplines in which many 'students' manifest difficulties that compromise the relationship with the subject. A student who comes out of secondary school has a long series of 'failures' accompanied by the conviction that she can never do mathematics because she is not good at it. The problem lies in identifying errors and difficulties in mathematical learning with the conviction that the absence of errors certifies the absence of difficulties and on the other hand the absence of difficulties guarantees the absence of errors (Zan, 2007 (A)). This identification leads to the didactic objective of obtaining the greatest number of correct answers by nourishing the "compromise of correct answers" (Gardner, 2002): on the one hand the teacher chooses activities that are not "too" difficult and on the other hand the students elaborate the answers expected by the teacher in a reproductive way. Of course, this method does not guarantee any learning, revealing itself dangerous and counterproductive (Di Martino, 2017). Moreover, with it the fear of making mistakes arise and also the conviction that mathematics is not for everyone (for instance: you can't study mathematics if you do not have a good memory!) (Zan, Di Martino, 2004). In order to face the identification of difficulty-error, there is, therefore, a need to revolutionise the conception of error and to convey to students that ''making a mistake at school may not be perceived as something negative to avoid at all, because it could be an opportunity for new learning (and teaching) opportunities to be exploited'' (Borasi,1996). The Inquiry model is a teaching-learning model that proposes a positive and fundamental role of errors in mathematics teaching. This model sees knowledge as a dynamic process of investigation where cognitive conflict and doubt represent the motivations to continuously search for a more and more refined understanding. Therefore, instead of eliminating ambiguities and contradictions to avoid confusion or errors, these elements must be highlighted to stimulate and give shape to ideas and discussions. Questions such as "what would happen if this result were true?" or "under what circumstances could this error be corrected?" lead to a reformulation of the problem where the error is only the Viviana Ventre, Eva Ferrara Dentice, Roberta Martino 114 starting point for a deeper understanding. Communication in the classroom plays a fundamental role, and so does the conception of mathematics as a humanistic discipline: the teacher provides the necessary support for the student's autonomous search for understanding, who in turn is an active member of a research community (Tematico, Pasucci, 2014). Learning turns out to be a process of constructing meanings, and in this way, the students also understand that what is written in textbooks is the result of debates and arguments and not simply something for its own sake ("falling from the sky"). 2.2 Cooperative learning: development of disciplinary and social skills Some studies highlight the need to build learning teaching models that take into account students' emotions, perceptions and culture based on the idea that human learning has a specific social character (Radford, 2006). The collaborative group and peer tutoring are two models that take on both the disciplinary dimension and the affective and social dimension and facilitate discussion in the classroom. In fact, in most cases, the teacher cannot give everyone the opportunity to express themselves, nor is he able to solicit the interventions of those who are not used to intervene. Collaborative learning, instead, sees the involvement of all the students in two successive moments: first within the individual group and then in the final discussion in class. The necessary conditions for such learning are positive interdependence and the assignment of roles: the first is reached when the members of the group understand that there can be no individual success without collective success; the second condition allows the distribution of social and disciplinary competences among the various members of the group favouring collaboration and interdependence. The recognition of roles also helps to overcome problems such as low self-esteem or a sense of ineffectiveness, allowing social skills to grow: knowing how to make decisions, how to express one's own opinions and listen to those of others, how to mediate and share, how to encourage, help and resolve conflicts are skills that the school must teach with the same care with which disciplinary skills are taught. Dialogue among peers guarantees greater freedom and spontaneity: the majority of students identify that among peers there is no fear of expressing doubts and perplexities, the main motivation that justifies the effectiveness of such models (Baldrighi, Pesci, Torresani, 2003; Pesci, 2011). 2.3 Recovery and enhancement interventions: breaking the educational contract The variety of possible processes, the fact that behind correct answers there can be difficulties and that some mistakes can come out of significant thought processes, brings important elements to support the criticism of the Teaching as a decision-making model: strategies in mathematics from a practical requirement 115 identification between mistakes and difficulties. For example, the incorrect resolution of a problem is not necessarily due to the inability to manage the mathematical structure of the proposed situation but is probably due to a lack of understanding of the problem itself. The understanding of a text is not always immediate because it involves the student's personal knowledge of common words and scripts. Understanding is, therefore reduced to a selective reading that aims to identify the numerical data and the right operations suggested by keywords (Zan, 2012). Recovery interventions must therefore be based on the analysis of the processes that led the student to make mistakes, shifting the attention from the observation of errors to the observation of failed behaviour with the sole objective of change. The student, in turn, must take responsibility for her own recovery and therefore there is a need for teaching that makes her feel that she is the protagonist of new situations and not simply the executor of procedures to be applied to repetitive exercises (Zan, 2007 (B)). The teacher must propose exercises and problems that do not favour a mechanical approach but question the rules that pupils are used to use and that form part of the so-called teaching contract (D'Amore, 2007; D'Amore, Gagatsis,1997). The idea of a didactic contract was born to explain the causes of elective failure in mathematics, that is, the kind of failure reserved only for mathematics by students who instead do well in other subjects. The didactic contract holds the interactions between student and teacher and is made up of "the set of teacher's behaviours expected by the student and the set of student's behaviours expected by the teacher" (Brousseau, 1986). This explains the students' belief that a problem or exercise always has a solution because it is the teacher's job to make sure that there is only one answer to the proposed question and that all the data is necessary (Baruk, 1985). In Bagni (1997) the following goniometry test is proposed to fourth-year students in three classes of scientific high school (students aged 17 to 18). Determine the values of x belonging to ℝ for which it results: a) sinx = 1 2Τ b) cosx = 1 2Τ c) sinx = 1 3Τ d) tgx = 2 e) sinx = 𝜋 3Τ f) cosx = 𝜋 2Τ g) sinx = ξ3 h) cosx = ξ3 3Τ Table 2.1 Experiment in Bagni, 1997. Remember that the goniometric functions are often introduced by making initial reference to the values they assume in correspondence to relatively common angles of use, so we have the well-known table shown in the next page (Table 2.2.) Viviana Ventre, Eva Ferrara Dentice, Roberta Martino 116 x 0 𝜋 6Τ 𝜋 4Τ 𝜋 3Τ 𝜋 2Τ 2 𝜋 3Τ 3 𝜋 4Τ 5 𝜋 6Τ 𝜋 … sinx 0 1 2Τ ξ2 2Τ ξ3 2Τ 1 ξ3 2Τ ξ2 2Τ 1 2Τ 0 … cosx 1 ξ3 2Τ ξ2 2Τ 1 2Τ 0 − 1 2Τ − ξ2 2Τ − ξ3 2Τ -1 … tgx 0 ξ3 3Τ 1 ξ3 n.d. −ξ3 -1 − ξ3 3Τ 0 … … … … … … … … … … … … Table 2.2 Values assumed by common angles where “n.d.” is “not define”. Let us now examine the test: agreed time 30 minutes and pupils were not allowed to use protractor tables nor scientific calculator. It has been conceived with: • two "traditional" questions (a), (b); • two possible questions, but with the results not included between the values of x "of common use" (c), (d); • two impossible questions (e), (f) but with values (of sinx and cosx) that recall the measurements in radians of "common use" angles (𝜋/3, 𝜋 /2); • two questions (g), (h) where the first impossible and the second possible. They propose instead values (of sinx, cosx) that are included in the table referred to the angles "of common use" but in relation to other goniometric functions (tgx, cotgx). Well, as far as the answers to the questions (e), (f) are concerned, the didactic contract has led some pupils to look for solutions anyway; and the "solutions" that most spontaneously presented themselves to their mind are the ones that they see associated, in the case of the sinus function, the two values 𝜋/3 and ξ3 2 Τ and, in the case of the cosine function, the two values 𝜋 /2 and 0. So we have, for instance, the following errors: sinx = 𝜋 /3 so x = ξ3 2 Τ cosx = 𝜋 /2 so x = 0 As far as the answers to questions (g), (h) are concerned, the reference to the tangent function was clearly expressed in the answers of some students: also in this case, some students, not finding the proposed values among those corresponding to the most frequently used x values (for the sine and cosine functions, in the table above), were induced to look for another correspondence in which the proposed values are involved. We then find errors such as: if sinx = ξ3 , then x = 𝜋 /3 if sinx = ξ3 , then x = 𝜋 /3+k 𝜋 What has now been pointed out obliges us to conclude that the need that leads the student to always and in any case look for a result for each proposed exercise is unstoppable: breaking the teaching contract can be used as a Teaching as a decision-making model: strategies in mathematics from a practical requirement 117 teaching strategy to overcome the mechanical approach used by the students and enhance knowledge (Bagni, 1997). 3 Concept image ad concept definition These notions were developed to analyse the learning processes of mathematical definitions (Tall and Vinner, 1981). Concept image is the whole cognitive structure related to the concept and includes all mental images, the properties and processes of recall and manipulation associated with a concept, bringing into play its meaning and use. It is built through years of experience of all kinds, changing with the encounter of new stimuli and the growth of the individual. The concept definition is the set of words used to specify a concept and turns out to be personal and can often differ from the formal definition because it represents the reconstruction made by the student and the form of the words he uses to explain his concept image. It can change from time to time and for each individual the concept definition can generate its own concept image which can be called in this case concept definition image. The acquisition of a concept occurs when a good relationship is developed between the concept name, the concept image and the concept definition. Students tend to learn definitions in a mechanical way and this can lead to conflict factors when concept image or concept definition are invoked at the same time which conflict with another part of the concept image or concept definition acquired on the same concept. To explore this topic a questionnaire was administered to 41 students with an A or B grade in mathematics. They were asked: "Which of the following functions are continuous? If possible, give your reason for your answer." Figure 3.1 Images from Tall and Vinner, 1981. We see that the concept image of this topic comes from a variety of resources such as the colloquial use of the term “continuous” in phrases such as “It rained all day long”. So, often the use of the term “continuous function” implies the idea that the graph of the function can be drawn continuously. The answers are summarised in the table shown in Figure 3.2. Viviana Ventre, Eva Ferrara Dentice, Roberta Martino 118 Figure 3.2 Tables from Tall and Vinner, 1981. It Summarises the results of the experiment. The reasons given to justify the discontinuity of f2(x) and f4(x) are of the type: “The graph is not in a single piece”, “There is no single formula”. In these answers, we see that many students invoked a concept image including a graph without any interruption or a function defined by a “single formula”. Instead, there are many continuous functions that conflict with the concept images just mentioned as the following: 𝑓ሺ𝑥ሻ = ൜ 0 ሺ𝑥 < 0 𝑜𝑟 𝑥2 < 2ሻ 1ሺ𝑥 > 0 𝑜𝑟 𝑥2 > 2ሻ whose graph is: Figure 3.3 Image from Tall and Vinner, 1981. It represents the function defined above. The idea that emerges from similar issues is that mathematical concepts should be learned in the everyday, not technical, way of thinking, starting with many examples and non-examples through which the concept image is formed and then arriving at a formal definition. Students should use the formal definition, but in order to internalise the concept it is necessary to aim at cognitive conflicts between concept image and concept definition. To do this it is necessary to give tasks that do not refer only to the concept image for a correct resolution, inducing the students to use the definition (Baccaglini-Frank, Di Martino, Natalini and Rosolini , 2018 (B)). 4 Teaching as a decision problem Today more than ever, the world of education has to work on the construction of personalities that can favour to all the students with freedom of choice and reactivity. The social context in which we live is complex because it comprehends factors of unpredictability and uncertainty: the educational systems have the job to provide a path that aims to thought and action autonomy. Teaching as a decision-making model: strategies in mathematics from a practical requirement 119 The school, therefore, has an orientation character, where the term “orientation” indicates a continuous and personal process that involves awareness, learning and education in choice (Biagioli, 2003). In particular, placing orientation as the main purpose of teaching "means developing strategies, methodologies and contents aimed from the acquisition of awareness to understanding the complex society and the mechanisms that govern the world of studies and work" (Guerrini, 2017). To give the proper and necessary instruments to the student, in order to activate the auto-orientation processes, the teacher has to chose what the best didactic strategy is. Therefore, on an operational point of view, the teaching is a decisional problem and has to be faced as it is. Indeed, we can speak of decision when in a situation there are: alternatives (being able to act in several different ways), probability (the possibility that the results relating to each alternative will be achieved) and the consequences associated with the results. Such factors are characteristic of the school world. So, to realise the best didactic strategy it is necessary to start with a representation of the problem: only through the calculation of the expectations and the evaluation of the results, it is possible to choose the right option. Decisions can be studied in terms of absolute rationality or limited rationality. The first model ideally combines rationality and information by preferring the best alternative; the second recognises the objective narrowness of the human mind by proposing the selection of the most satisfactory alternative (Lanciano, 2019-20). It is important to emphasise that the consequences of a decision are determined also by the context in which the decision-making process is developed. On the basis of the decision maker's knowledge of the state of nature. we distinguish various types of decisions: • decisions in a situation of certainty: when the decision-maker knows the state of nature; • decisions in risk situations: when the decision-maker does not directly know each state of nature, but has a probability measure for them; • decisions in situations of uncertainty: when the decision maker has neither information on the state of nature nor the probability associated with it. The decision maker can adopt two kinds of approaches: • Normative approach. which bases the choice with reference to rational decision-making ideals; • Descriptive approach which analyses how to make a decision based on the context. So, the teacher has to consider on the basis of the objectives and the context the various alternatives, and for each one of them, the possible consequences. For each pair (alternative, circumstance) the teacher obtains a result according to a utility function. Viviana Ventre, Eva Ferrara Dentice, Roberta Martino 120 However, the decision is subjective: it is based on the criterion of obtaining a maximum value for the utility function. Moreover, even if the choice is rational, it is made in terms of limited rationality because, in general, there are few alternatives, but it increases as the teacher expands his/her culture and experience (Delli Rocili, Maturo, 2013; Maturo, Zappacosta, 2017). 4.1 A model for evaluating educational alternatives Multi-criteria decision analysis (MCDA) provides support to the decision maker, or a group of decision makers, when many conflicting assessments have to be considered, especially in data synthesis phase while working with complex and heterogeneous pieces of information. Let A = {A1, A2, ..., Am} be the set of the alternatives, i. e. the possible educational strategies. Let O = {O1, O2, ..., On} be the set of the objectives that we want to achieve. Let D = {D1, D2, ..., Dk} be the set of the decision making processes. The first phase consists of the establishment of a procedure that is able to assign to each couple (alternative Ai, objective Oj) a pij score. In this way, the responsible for the decision measure the grade in which the alternative Ai satisfies the objective Oj. Assume that pij is in [0, 1], where: • pij = 0 if the objective Oj is not at all satisfied by Ai; • pij = 1 if the objective Oj is completely satisfied by Ai. At the end of the procedure we obtain a matrix P = [pij] of the scores which is the starting point of the elaborations that lead to the choice of the alternative, or at least to their ordering, possibly even partial (Maturo, Ventre, 2009a, 2009b). There may be constraints: it could be necessary to establish for each objective Oj a threshold j > 0, with the constraint pij ≥ j, for each i. Furthermore, through a convex linear combinations of alternatives Ai it is possible to take into consideration mixed strategies that will have the following form: A(h1, h2, ..., hm) = h1 A1 + h2 A2 + ... + hm Am with: • h1, h2, ..., hm non-negative real numbers; • the hi’s are such that h1 + h2 + ... + hm = 1; The number hi can represent the fraction of time in which the teaching strategy Ai is adopted. If we consider also the mixed strategies, then the single alternatives Ai are called pure strategies. The mixed strategies are particularly considered in presence of “at risk” alternatives: these situations have high scores for certain objectives and low for others (possibly below the threshold). It is appropriate to construct a ranking of the alternative educational plans, i. e., a linear ordering of the alternatives that takes into account the objectives which contribute to the most suitable formation of the student. Such a ranking can be usefully obtained by means of the application of the Analytic hierarchy process, a procedure due to T. L. Saaty (1980, 2008). Teaching as a decision-making model: strategies in mathematics from a practical requirement 121 4.2 The Analytic Hierarchy Process: attributions of weights and scores The Analytic Hierarchy Process (AHP) is both a method and a technique that allows to compare alternatives of different qualitative and quantitative nature, not easily comparable in a direct way, through the assignment of numerical values that specify their priority. The first thing to do is represent the elements of the decision problem through the construction a hierarchical structure. Indeed, the Analytic Hierarchy Process is based on the representation of the problem in terms of a directed graph G = (V, A). Let us recall that (Knuth, 1973): • a directed graph, or digraph, is a pair G = (V, A), where V is a non-empty set whose elements are called vertices and A is a set of ordered pairs of vertices, called arcs; • a vertex is indicated with a Latin letter; for every arc (u, v) u is called the initial vertex and v the final vertex or end vertex; • an ordered n-tuple of vertices (v1, v2, ..., vn), n > 1, is called a path with length n -1, if, and only if, every pair (vi, vi + 1), i = 1, 2, …, n-1, is an arc of G. Furthermore, in our context, we assume the following conditions be satisfied from a directed graph: • the vertices are distributed in a fixed integer number n ≥ 2 of levels; each level is indexed from 1 to n; • there is only one vertex of level 1, called the root of the directed graph; • for every vertex v different from the root there is at least one path having the root as the initial vertex and v as the final vertex; • every vertex u of level i < n is the initial vertex of at least one arc and there are no arcs with the initial vertex of level n; • if an arc has the initial vertex of level i