How can we take into account student conceptions of the facial angle in a palaeontology laboratory work?

This study investigates student conceptions of the facial angle as a way to attain understanding elements of the theory of human evolution. The chosen laboratory work involved determining the species of a human cranium, and students had to design and write down their own experimental procedure. Three versions of the laboratory work were carried out leading to different student productions. Three aspects will be presented in the present paper, which are related to the three conceptual difficulties that appeared in our a priori analysis: the importance of students’ everyday knowledge of angles and of anatomy of human crania, the problem of knowing how many points make up an angle, and finally, the way in which students determined a reference system to construct an angle. Context and theoretical background This study is a preliminary to the development of Copex, an Intelligent Learning Environment that allows students to prepare experiments in biology, chemistry, geology and physics. In particular, the environment will scaffold the design of experimental procedures. The aim is to assist the teacher as well as the learners in present-day laboratory work practices. The development of Copex is based on task analysis (Clark, Feldon, van Merriënboer, Yates, & Early, 2006) by structuring the lab work activities in a task tree. At the top of the tree, a scientific problem is proposed, which generates tasks and sub-tasks. The actions at the lower levels of the tree represent the referent experimental procedures. The task tree structures the learning environment and can be used to conceive the laboratory work situation and to analyze student productions. The present research aims at analyzing student productions when they have to write down an experimental procedure, as compared with an expert procedure, and at identifying the difficulties encountered by students. To investigate these questions, a team composed of eight researchers and four teachers has built and tested five laboratory works, with about three hundreds students in either the terminal level of the upper secondary school (ISCED level 3A-17/18 years old), or the first level at science university in Grenoble, France. Students had to find the procedure to determine the facial angle of several hominid crania. This value depends on the prognatism of the cranium, which is an evolution indicator: the more recent the species is, the more prognatism decreases and the more facial angle increases. The study was part of a design experiment for testing a new evaluation procedure of experimental skills in the French baccalaureat. In fact, the evolution theory makes up a very important part (one third) of the French terminal level biology curriculum. This study is innovative to the extent that it deals with a new situation in laboratory work. Indeed, teachers usually suggest an experimental procedure to students to be followed, but students themselves almost never get to conceive it. An intelligent learning environment, which helps students and teachers design an experimental procedure, seems a promising approach to help students improve on the meaning of their scientific knowledge when doing laboratory works including communication between students. Design experimental procedure for helping students to learn scientific knowledge. Many studies have shown a lack of understanding by students in most experimental activities in laboratory work. The roles and functions of practical activities in sciences are presented in the official programs and instructions for school. In France, the introduction in 2001 of a test for the evaluation of the experimental capacities (ECE) in the baccalaureat has reinforced this role. The Committee on High School Laboratories (2006) defines practical work as: « physical manipulations of the real world substances or systems, interactions with simulations, interactions with data drawn from the real world, access to databases or remote access to scientific instruments and observations ». For Hodson (1990) “at the root of the problem is the unthinking use of the laboratory work”. For Millar (2004), another problem relates to the way students interpret and explain data, facts, and relationships when they work in laboratories; ideas and explanations do not simply emerge from the data. Several other studies have shown that the application of a so-called ‘cookbook mode’ in practical work is not an efficient way to construct scientific knowledge (Tiberghien, 2001). In the context of the experimental method, experimental procedures play an important role for putting theories to the test. Following Popper (1959), a theory is scientific only if it is falsifiable. Other scientists should be able to produce the same results, following the same procedure, in the same conditions. Designing an experimental procedure is therefore crucial to train students to the experimental scientific method. When students design an experimental procedure, they have to make decisions about the parameters they choose and also have to raise the issue of precision, which is the possibility for a measurement to be reproduced consistently. In doing so, students need to mobilize their own knowledge model. For the classroom context, we have translated falsifiability into three explicit criteria: relevance (give an answer to the scientific problem), reliability (reproducibility: obtain the same value) and communicability (can be used by another person). To internalise the aim and the meaning of the experiments, we suggested that students first write down the detailed experimental procedure before executing it, to minimize the use of a cookbook recipe coming from an external point of view (Keys, 1999). The final objective of our research is to propose conditions and guidance to make the student autonomous with respect to experimental design and to allow a reflected implication of the teacher (Brousseau, 1989). Some conditions to make students design an experimental procedure The activity of designing an experimental procedure with the aim of obtaining data to solve the initial problem is composed of three steps: reflexion phase, writing phase (text, diagram, drawing, ...) of the procedure, experimental execution. The steps depend on each other, and there is no linear order. In each step, students mobilise conceptions, which lead to choices, decisions and actions (Marzin, d’Ham & Sanchez, 2007). We looked at student conceptions when designing and writing down the experimental procedure for solving a palaeontology problem. Students encounter difficulties when they design an experimental procedure: in writing a text, in correctly analyzing the situation and in referring to another situation that is probably more common for them. For example, students do not take into account the question of the precision (Marzin, d’Ham, & Sanchez, 2007). Students have to carry out tasks that are too numerous and too varied, including the control of precision of the measurements (Trochim, 2006), which is usually not allotted to them. Students have no opportunity to think about criteria in specifying parameters. To settle these difficulties, we conceived other situations and we defined conditions in which students design the experimental procedure. Our approach includes: a knowledge analysis combined with a task analysis, an evaluation of the distance between the tasks to be done and the knowledge to be learnt, a selection of the tasks that are allocated to the students, and those allocated to the teacher, an analysis to anticipate the difficulties that the students may encounter and a proposition of related feedbacks from the components of the environment, and finally the construction of a situation involving communication between students. Expert knowledge about facial angle In palaeontology, facial angle is defined as “the angle that is determined by the intersection of a line connecting the nasion and prosthion with the Frankfort horizontal plane and is used as a measure of prognatism” (medical.merriam-webster 1). The nasion (see figure 1) is the intersection of the frontal and two nasal bones of the human skull. Its manifestation on the visible surface of the face is a distinctly depressed area directly between the eyes, just superior to the bridge of the nose. The prosthion is the point located between the two central incisors. The Frankfort horizontal plane is “a plane used in craniometry that is determined the highest point on the upper margin of the opening of each external auditory canal (Po) and the low point on the lower margin of the left orbit (O) and that is used to orient a human skull or head usually so that the plane is horizontal” (medical.merriam-webster 2). Na: nasion Pr: prosthion O-Po: Frankfort horizontal plane. Figure 1. Measurement of the facial angle (source Naddam). Designers of school curricula have simplified the formulation of the terms used for the points and do not mention the Frankfort plane (see Figure 2). Figure 2. Facial angle representation in school curriculum (source: French Ministry of Education) Student conceptions of an angle In developing a teaching situation on prognatism, we were confronted by the fact that the determination of facial angle strongly builds on prior mathematical knowledge about points, lines and angles. In short, students need to know that 1) a point is an exact location in space, 2) a line is an infinitely thin, infinitely long, perfectly straight curve containing an infinite number of points, 3) exactly one line can be found that passes through any two points providing the shortest connection between the points, 4) if two lines in a two-dimensional plane are not parallel, there is exactly one point that lies on both of them, 5) an angle is the figure formed by two lines sharing a common endpoint, called the vertex of the angle, 6) an angle expresses the difference in slope between two lines meeting at a vertex without explicitly defining the slopes of the two lines. In her synopsis of the literature on the notion of the angle in secondary school, Vadcard (2002) retraces specific difficulties and three of these might play a role in the determination of facial angle. Figures versus drawings The first difficulty is related to the fact that an angle is a mathematical object. Note that a geometrical figure, as a mathematical object, has to be distinguished from a particular drawing. Pupils often confuse a mathematical object (figure) with a particular representation (drawing) of it (see also Duval, 1995). More specifically, in interpreting a graphical depiction, such as two lines meeting at one point, how does one selects the relevant features prior to knowing the definition of an angle? Pupils are influenced by the spatial-graphical characteristics of a drawing, they may, for instance, wrongly measure the length of two lines in order to evaluate the size of the angle. In looking for lines on the cranium for constructing facial angle, pupils may try to reproduce familiar prototypical angles found in textbooks and other pedagogical material, rather than looking for lines that are determined by characteristics of crania.