A contribution to the analysis of the interactions between the history of science and science education. An elaboration of an educational tool of the optical mechanism of vision for primary and secondary school. (2004)
IUFM de Reims, LDSP Université Paris7-Denis Diderot
Université Paris1-Panthéon Sorbonne
This thesis presents: the working out and the analysis of an educational tool inspired by the history of the optical mechanism of vision.
We first investigated 5 to 12-year old pupils’ reasoning about vision. Most of them explained it as the result of something coming either from the object or from the eye. Moreover, some of them think that light penetrates the eye only when they are dazzled.
Such ideas can be found in the ancient and medieval history of science. In particular, Ancients disagreed on the direction of vision until Alhazen opened the way to a consensus arguing, in the 11th century, that light could be a stimulus for the eye.
Our tool, a short drama ‘Dialogue on the ways that vision operates’, refers to those historical elements, especially to the controversy over the direction of vision and Alhazen’s ideas about light. It was written thanks to an historical reconstruction we made for an educational purpose from original books of Aristotle, Lucrecius, Plato, Empedocles and Alhazen. As we knew learners’ difficulties and conceptions about vision, we tried to establish a conceptual route that should be used as a cognitive pathway for the students. In this research, we make the hypothesis that this conceptual route which starts from the controversy over the “direction” of vision enables the learners to assimilate a correct explanation of the mechanism of vision. The fact that they agree to take this path could benefit from the opportunity given to them to relate to those representing extra or intromissionist ideas.
The Dialogue on the way that vision operates is a conversation between 3 characters discussing explanations of sight. Starting from a supposed debate between students, first, we wished to encourage the emergence of a consensus about the “direction” of vision; in other words, lead the majority to accept the object?eye direction. Concerning this point, we saw as essential the idea of unity of functioning of the 5 senses presented by Aristotle. In the De Anima, he places vision within the larger context of the operation of the soul and writes: “Sensations are meant to be moved, to suffer (…) every sense is driven by its own sensitive organ”. Supposing that most students should be convinced by Aristotle’s words and accept an intromissionist functioning modality, we then had to bring them to identify the agent which is responsible for vision. This next step was actually very complex. First it required that students carry out a conceptual change since they have to build a conceptual object the nature of which may clash with the one that is generally given. Second, we needed to clarify the paradox mentioned above: for the students the fact that light penetrates the eye dazzles the observer. The issue of light blinding the observer leads Alhazen to declare that “vision will occur only as a result of something coming from the visible object to the eye (…). What comes from the object to the eye is nothing but the form of the light and colour” (Kitab al manazir, book 1, chap 6), this marked the beginning of optics, “the science of light “. According to Alhazen, if a strong light disturbs the eye and hurts it, it is because it is a property of sight to be affected by light. And to come to the conclusion that light is the stimulus of the sense of sight, he thinks of light not only as a conceptual entity but also in terms of the quantity that the objects (luminous by nature or by diffusion) send out to the eye. Therefore, it is with a quantitative treatment that Alhazen manages to define light as the stimulus of sight. And it was the same treatment that we offered our students: to reason in terms of “quantity” of light and no longer in terms of “light” only.
This text was integrated in a teaching-learning sequence (TLS) and it was presented to six pairs of students aged 12 or 13. The analysis of this TLS shows that the learning process can take advantage of the opportunity offered to the students to identify themselves with the scientists staged in the drama.
This look back on the history of the theories of vision gave us the opportunity to reflect on the question of supposed analogies between the historical development of ideas and the individual process of assimilating scientific knowledge. In his essay on optics, Alhazen relies on a situation of dazzle to convince the reader that light has an effect on the eye. This empirical acknowledgement leads him to formulate the idea that vision is the result of light penetrating the eyes. The evocation of a situation of being dazzled by light leads the majority of the students to think that the entry of light in the eye prevents vision. What appears to be a historical condition of the development of ideas in optics constitutes a major obstacle to the students’ understanding of the mechanism of vision. Focusing on the students’ reasoning enabled us to realise the effort of abstraction made by Alhazen. A few years ago, in an identical context, Thomas Kuhn, the philosopher wrote: ‘Part of what I know about how to question dead scientists has been learned by examining Piaget’s interrogations of living children’. (Kuhn, 1977). If the historical analysis gives an idea of the level of difficulty of a teaching matter, science education enables us to propose a particular reading of the history of theories of vision and contemplate a conceptual path from a specific point of view. The ideas that have stood out come directly from the history of science and we organised them in reference to the difficulties that the students face. It was done in order to help a learning process which favours the understanding of a rather abstract explanation.
Key words:Teaching-learning sequences, teaching experiment, history of science, vision, light, Alhazen.
Reference:De Hosson C. and Kaminski W. (2007, in press) Historical controversy as an educational tool: Evaluating elements of a teaching-learning sequence conducted with the text ‘Dialogue on the ways that vision operates’. International journal of science education, to be published.
Cécile de Hosson
LDSP, Université Paris7-Denis Diderot
Tour 24-34, 1e étage, porte 109, case 7086
75251 Paris cedex 05