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Ask most 13-year-olds to explain what happens when you toss a coin in the air, and they will probably say: ‘Well, you give it a force and it goes up until that force is used up then gravity takes over and pulls it down.’

An 11-year-old argues that if you put more air into a beachball, it will make it weigh less ‘because air is light – it makes things float’. Adolescent students typically argue that a magnet would not attract iron on the Moon because there is no air for the magnetic force to travel through (see Figure 1).FIG-mg17755901.jpg

These are all examples of commonsense notions of the physical world widespread among schoolchildren. The ideas ‘make sense’ of common events we experience in daily life. Air does appear to have a ‘weightless quality’; bubbles rise through water; a blown-up balloon falls more slowly to the ground than a deflated one.

Over the past 20 years science teachers and cognitive psychologists have contributed to a growing body of research literature documenting children’s informal ideas about natural phenomena and the way these develop as children go through the school years. The emerging picture suggests that even children from different cultures can have similar informal models about particular phenomena. In some cases, these informal models differ from and even contradict the scientific ideas that children are presented with in school. Research suggests too that these notions may persist into adulthood alongside the science that people learn in school. An understanding of these informal models is fundamental to the development of more effective ways of teaching science.

Students’ informal ideas about mechanics have been studied most. In an influential study in 1979 at the University of Paris, Laurence Viennot asked French, Belgian and British secondary and university students questions about moving objects to probe how they related force and motion. One of the questions concerned six juggler’s balls, all at the same height above the ground, but at different points in their trajectories (see Figure 2).FIG-mg17755902.jpg

Many students related the speed of an object to the magnitude of the force acting on it, reflecting a common-sense notion that there is a force in a moving object which keeps it going. Moving objects have an ‘internal force’ of motion given to them when they are pushed. The object then moves under the influence of this ‘internal force’, which eventually gets ‘used up’ or ‘drains away’, as the object finally comes to rest. Reasoning of this kind leads students to construe cases of constant motion, such as a parachutist descending from a plane at a constant speed, or a cyclist pedalling at a constant speed, as cases where the force in the direction of motion must be greater than the force opposing the motion, otherwise the object would stop. In this way informal ideas interfere with what is taught. Indeed in many cases students incorporate new experiences and taught ideas into their existing notions rather than changing their existing notions to take account of the new information. For example, children think of food as substances taken in by animals which they need to keep alive. In the case of plants, children extend this notion to plants taking in food such as water and nutrients through their roots. Unless this notion is dealt with explicitly, it will interfere with their understanding of the process of photosynthesis.

But children’s informal notions also evolve as they get older. When children in a classroom are asked to say where there is light, five-year-olds typically identify light as the source (the light bulb or the bright window) or the effect (a patch of brightness on the wall). Older children identify something in the space between. They will say that when a light switch is turned on, for example, the room is filled with a ‘bath of light’ which enables them to see things. By early adolescence, children tend to suggest that light travels – leaving a source and illuminating an object. But a link between light and sight is more difficult to establish. Some children tend to use the idea of visual rays emanating from their eyes to explain how they see, an idea which is reinforced by the need for observers to turn to ‘look at’ things they see. In explaining how she could see a box in front of her, a 13-year-old used both the notion of light rays from a source and visual rays from the eye in her argument:

‘The eye sees like this . . . it comes out like this (draws lines, outwards from picture of an eye). The eyes haven’t got any light of their own, so they have a light that lights up what you want to see’ (indicating light from external source striking observed object).

A Swedish study probed the way children reason about light and sight (see Figure 3). In this survey, only a few secondary schoolchildren used a model of light travelling outwards in space beyond what could be perceived by an observer.FIG-mg17755903.jpg

Studies of children’s reasoning about the Earth and grav-ity have generated interesting cross-cultural comparisons. Researchers asked children to consider the conceptual problem of how their immediate perceptions of the world around them as flat can be interpreted in terms of the Earth as a sphere, an image which is now so familiar through the media. In a pioneering study in 1976, Jo Nussbaum at Cornell University in Ithaca, New York, questioned 7-to 14-year-olds using drawings and models and identified five notions underlying children’s reasoning. These vary from a Flat Earth notion, through a notion of the Earth as a hollow sphere with life existing on a platform at the bottom, through to a notion of a spherical Earth with gravity (that is, the direction which things fall when released) acting towards the centre.

Theories that matter

At the Children’s Learning in Science Research Group at the University of Leeds, we have been exploring children’s ideas about matter. We wanted to find out whether children think about the materials and substances experienced in daily life, such as water, metals, plastic and air, as continuous ‘stuff’, or as being made of small pieces. How do they think about the processes involved when matter seems to appear and disappear from nowhere such as when condensation appears on a window, when sugar dissolves in tea or when paper burns to a flaky ash?

Children in their later years at primary school do seem to have informal notions about matter and what it is made of. They tend to reason about what happens when substances dissolve or melt in terms of the substance being made of little ‘bits’. But these tend to be thought of as bits of the macroscopic substance which retain all the physical properties of that substance, such as colour and temperature.

Children’s conceptions about air and gases undergo some interesting changes with age. To assess what young children thought, we asked 5-and 6-year-olds to draw a picture of the room they were in and then to colour in where they thought air was present. The drawings revealed colourings around the windows, under the doors, and tubes of air coming from people’s mouths. At this age, air is seen as a breeze or draught; children have not developed the concept of still air all around them.

This change happens between the ages of 7 and 9, when children will, for example, spontaneously use the notion of the existence of air to explain why water does not enter an upturned jam jar which is pushed down in a bowl of water. At this age, children think of air as a kind of stuff, albeit invisible, which takes up space, but is weightless or has negative weight. Only later in the secondary years do some pupils come to appreciate that air has weight in a scientific sense.

Children also tend to think of air as a necessary medium through which forces at a distance can act. They think that gravity will not pull objects down in an evacuated tube; similarly, magnets will not attract iron nails on the airless surface of the Moon.

As these descriptions indicate, researchers have found definite patterns occurring in children’s informal ideas, with certain notions being more prevalent at certain ages. It also seems that in the evolution of their ideas, children construct intermediate models, such as air having negative weight or a ‘bath of light’ filling a room. These intermediate models go beyond features they perceive directly. The children are constructing certain conceptual entities, such as light existing in space or air having substance. These constructs become part of children’s models of how the world works, which they used as tools to reason with. Indeed, as several surveys have shown, many individuals will use these informal models, rather than the accepted science viewpoints, throughout their lives.

Common concepts across cultures

An interesting feature of these studies is the similarity in the models used by children from different backgrounds and the way these progress with age. These models probably arise through children’s experiences with physical phenomena. They enable children to anticipate events and to adapt their behaviour to the physical world: they ‘fit’ with their experiences. We should not be surprised by the common features in children’s models. Whatever the differences in children’s language or background, the physical world impinges on them in similar ways. They experience lifting and throwing things, manipulating materials, observing light and shadows for which these, often tacit, informal models are constructed. How these informal notions ‘fit’ with experience – the fact that they are ‘common sense’ – makes the students’ task of understanding formal science concepts more difficult.

Teachers of science are beginning to take into account these findings from studies of children’s informal theories and to recognise that when children first meet a topic in school science they may already have informal ideas about the phenomena. Surveys and interviews with students taking science courses in secondary schools show that in many cases children hold on to these notions very firmly despite teaching. We need to develop an approach to education that takes account of children’s informal notions. Effective learning in science involves students not so much ‘taking in’ new information as reorganising the notions they already have.

This work also has implications for curriculum planning. Studies of the evolution of children’s informal ideas in science through the primary and secondary years suggest that children tend to progress in their reasoning through a series of informal models. Information about these models, their prevalence at different ages and the sequence through which children tend to pass provides a basis for a more effective school curriculum. Such a curriculum could ensure that school science addresses children’s informal ideas and so contribute to maintaining young people’s involvement in and enthusiasm for science as a way of making sense of their environment.

Rosalind Driver is professor of science education at the Centre for Studies in Science and Mathematics Education at the University of Leeds.

Research groups in Britain investigating children’s informal ideas in science and their implications for teaching and the curriculum include the SPACE project at King’s College, London, the University of Liverpool and the Children’s Learning in Science Research Group at the University of Leeds.