K1.2 Investigative Skills
The ideas of experiment and investigation are central to science but problematic for students and some teachers especially if they do not understand or identify with the question being asked. This article explores some examples frequently used in science classrooms and looks at 'fair testing', the control of variables. The importance of being clear about the purpose and planning of practical work is stressed. Some of the recent research and development projects in this area are introduced.
This is one of 17articles whose main aim is to support the processes of teaching/learning between the science education tutor and the trainee science teachers with a focus on “teachers’ knowledge and understanding”. During a primary or secondary BEd, PGCE or GTP we hope that those learning to become science teachers will be able to challenge their own understanding of science and scientific concepts. Unit K0 specifically explores general issues relating to all the knowledge units - to the learning of science.
Standards: This unit specifically addresses Q14 but, appropriately used can contribute to and provide evidence of competence for many others of the standards especially Q4,6,7,8,18, 22 and 25.
Key words: Experimentation, Investigation, Fair test, Practical work, Variables.
Our students need to realise that children do not come to science as 'blank slates to be written on' or as ‘empty vessels to be filled’. They have ideas about why things happen. These naïve ideas are likely to differ from the accepted scientific view, and may remain uninfluenced, if our teaching ignores them and/or the students do not actively and intellectually become involved in the investigation itself. The first part of this unit, ideas and evidence, explored the nature of the scientific process, summed up by ideas and evidence, or guesswork and checkwork. Although scientific ideas are products of our imagination (or at least the imagination of scientists who thought them up), they do have to stand up to rigorous testing. The second part of this unit investigative skills examines how we can help intending teachers to cope with the experimental and investigative side to science, and covers, amongst others, the idea of making fair tests.
These questions can be used to generate discussion amongst trainee teachers:
1) Children left some seedlings to grow in a warm dark cupboard, and others on a cool window sill. They watered them both. The plants on the windowsill grew better than those in the cupboard. What does this tell you about:
(a) the effect of light and warmth on growing seedlings and
(b) about carrying out a scientific investigation?
2) Some children were testing a range of cars to see which went the furthest over the carpet. To make the experiment fair the children took turns in pushing the cars. Comment on this view of a ‘fair test’.
3) “We did the investigation three times to make it fair?” Comment on this pupil’s view
Intending teachers need to understand some of the problems faced by children as they undertake investigations. Primary teachers will need to establish the ground rules, but secondary teachers need to know the misconceptions that pupils may still retain as they enter their secondary education.
Question above illustrates two problems children often face in investigations:
- The need to decide what is meant by ‘better’?
- The need to change only one variable at a time.
Have the plants in the window grown better? They look greener and more healthy, but the ones in the cupboard are taller, but very yellow. If ‘better’ means taller then the cupboard wins! (In experiments with plant growth investigations should always start with growing plants that are as similar as possible - many investigations start with seeds so the two processes of germination and onward growth become confused - for more discussion see the units in Subject Knowledge - science 2).
Many pupils will claim that the experiment shows that the plants need light to grow well, but is it the extra light or the cooler conditions that have caused the window plants to look healthy.
Most intending teachers will see this as a problem of variables - you must only change one thing at a time if you want to pinpoint cause and effect. If you think it is light levels that affect a plant's growth, then place both plants by the window, but cover one in clear plastic, and the other in dark plastic. The only difference is light level. If, however, you think that warmth helps a plant, place them both in the dark (covered in black plastic), but one is put in a warm cupboard. (Or both can have light, with only one kept warm.)
Goldsworthy & Feasey (1994) have developed an approach that ensures that children
- distinguish input or independent variables (what you can change - the light levels, the warmth. . .) from the output or dependent variables (what you observe or measure - the number of leaves the plant has, the colour of the leaves, the height . . .)
- only change one variable at a time (either light level or temperature, but not both at once)
- identify the question they are asking (eg. “Is the number of leaves that grow on a plant affected by the light level?”)
- know that the test is fair (everything is the same for both plants except the light level)
- are able to record their results in a table or on a graph
- draw a conclusion that relates to the question they asked
For further details of their approach see download 2.1 Primary Investigations. Secondary trainee teachers should also be aware of this approach - their Y7 pupils are likely to have had experience of investigations in this format.
Question above relates to the idea of making a test fair. Young children are likely to see this a taking turns, rather than controlling variables. It can start in the reception class using the exaggerated error approach - when you ask children to see which car goes furthest, push one very gently and the other very hard. The children will cry out 'not fair' and start their progress on the road to understanding that you must keep everything the same (fair) except the one thing you are testing (type of car).
Investigations with two variables
As pupils enter the secondary school they will begin to do investigations where two variables are manipulated. Many investigations go wrong at this stage - see download 2c
Question 3 above, illustrates another misconception about ‘being fair’. ‘Fairness’ relates to variables, but taking multiple readings relates to reliability. If all your readings cluster neatly you can be sure that the result is reliable. If they scatter widely there is likely to be another variable at work that you have not controlled properly, and you cannot rely on your results. (It is a matter of judgement to decide whether a given set of results is sufficiently reliable for your purposes.)
Investigations with multiple variables
When scientists do observational experiments on complex systems that they cannot manipulate, such as the behaviour of animals in the wild, complex statistical methods are required to determine if a particular observed difference could have happened by chance or whether it might be 'real'. These are beyond the scope of primary science, but need to be explored when evidence is presented. Usually the statistical methods will allow an estimate to be made of the probability of an observed difference occurring by chance. If the probability of chance is more than 1 in 20 (0.05) then the difference is not usually accepted as real.
Question 3 above also needs attention, and is discussed in download 2c
Types of practical activity in science: Practical work has many uses in science - it is important that your trainee teachers identify the purpose every time they plan practical activities with children. It is also always important that the teacher does a risk assessment prior to any activity so that the risk can be minimised and the pupils know what to do if anything goes wrong. Pupils should also be encouraged to be aware of safety issues - although it remains the teacher’s responsibility. Anyway, here five of the most important reasons why we ask pupils to do practical work:
1. Gaining experiences
- describing, sorting, classifying (similarities and differences)
- starting point for investigations, questions, predictions, hypotheses
Before children can begin to think about why something happens they must have experienced it. Much of our work at Key Stage 1 will be in this category, eg children's first experience 'playing' with magnets.
2. Illustrations of scientific ideas
- give instructions of what to do
- illustrate concept or process for discussion
When you have challenged children's ideas about why something happens you may want them to test out this new idea you are giving them in a controlled environment. For example, asking them to feel their heart beat after exercise suggests a link between blood flow and supplying food and air to the muscles.
3. Making observations
- opportunity for use of knowledge and understanding
Observations cannot be naïve. What we observe is always a combination of the ideas stored in our brains, and the sense data we receive. Each child will observe only what they are able to make sense of. Asking children to 'observe' carefully is a good way of finding out what ideas they do have in their minds, eg asking them to observe and draw their shadows.
4. Basic skills
- selecting or using equipment
- communication skills (eg writing, drawing, making and interpreting graphs)
- techniques (eg measuring force, temperature etc)
Sometimes it is important to teach children how to use a particular technique or piece of equipment. It is much better to combine such introductions with an investigation, but the newness of the task means that you want the investigation to be simple. An example is learning to use a thermometer by leaving it around in different places and recording 'room temperature', or feeling the temperature of cups of water before and after mixing or sharing them. It is important, even here, that pupils should try to understand the question and have contributed to the purpose of measuring temperature, or at least predicted the temperatures about to be measured.
- arise from observations and discussions - pupils should understand and ‘own’ the discussion
- encourage pupils to think, plan, carry out and interpret
Investigations are the ultimate aim of children's practical work in school, and all trainee teachers should undertake an investigation , and attempt to assess their success as part of the process of coming to terms with what we are asking pupils to do in school. It is vital that pupils/students do not see the purpose of an investigation as being to gain high marks in an assessment.- clearly an assessment should be serious, but the marks ore an outcome of how the investigation is done and communicated NOT why an investigation is done.
Teaching scientific enquiry
The Science Enhancement Programme has developed some important resource material which our intending teachers can make use of. This is an extract from the SEP-King's Enhancing Enquiries in Schools (SKEES):
“Different kinds of enquiry place different emphasis on various skills and processes, so using a wider variety of enquiries offers new opportunities and contexts for teaching and learning scientific skills and procedures. The AKSIS project generated a range of strategies for developing specific scientific skills and processes, and these strategies will be advanced further in the SKEES project. The project is taking place in three phases:
- Development of scientific enquiries
- Trial of scientific enquiries in collaboration with teachers
- Development of exemplification materials and trialling with a wider sample
The work is being done at Kings - follow this link: http://www.kcl.ac.uk/schools/sspp/education/research/projects/skees.html
Anna Cleaves and Rob Toplis have written a paper for School Science Review entitled: "Assessment of Practical and Enquiry Skills: lessons to be learnt from pupils’ views"
They report research into the views of pupils from nine state-maintained secondary schools about assessed investigative work at Key Stage 4 (14 to 16 year-olds) in the English National Curriculum. It presents a discussion of pupils’ views about the role of the teacher, the timing of investigations in relation to curriculum content, time allowances and apparatus provided.
They conclude that there is little benefit in being trained to do a limited range of investigations at Key Stage 4. This situation seems to have arisen from a culture of high stakes assessment, where a difference between a GCSE grade D and a grade C is critical for comparing school with school and has had the widespread effect of conflating the teaching and assessment of investigations.
They support a less prescriptive assessment policy that relies less on a performance model for assessment and more on teachers’ professional judgement and decision-making. Such a policy would improve the scope and variety of investigative work.
Teachers may consider, in the light of the research they reported, that GCSE programmes starting in 2006 are an opportunity for reclaiming investigation for science learning by teaching science through investigation, and not divorced from it, thereby avoiding the confusions and lack of motivation depicted by the pupils who have to fulfil the Exam board criteria of 'standard' whole investigations.
The research is published in full in Toplis and Cleaves (2006)
Research into children's ideas has mainly concentrated on strands two, three and four of the National Curriculum. The best account of children's views about the nature of science and how science happens is in Driver et al (1996). Research suggests that children see no point in scientists doing experiments if they already suspect what might happen. Most children have a 'eureka' view of science. A scientist does an experiment, not knowing what might happen and suddenly out plops a discovery at the end.
Driver suggests that it is not until pupils sit their GCSE that they truly begin to see experiments as testing ideas - that scientists do know what they think (and hope!) will happen, because they are testing an idea that they are trying to believe in.
- Goldsworthy A & Feasey R (1997) Making Sense of Primary Science Investigations Revised Edition Revised By Stuart Ball. Hatfield: ASE isbn 0863572820
- QCA/DfEE (1988) Science: A Scheme of Work for Key Stages 1 and 2 London: QCA (See Science Teachers' Guide Table C pp16-17 - Experimental and Investigative Science from Years 1 to 6)
- Ross K (1998) Brenda Grapples with the Properties of a Mern in Littledyke M & Huxford L (eds) (1998) Teaching the Primary Curriculum for Constructive Learning London: David Fulton
- Toplis and Cleaves (2006) Science Investigations: the views of 14 to 16 year old pupils. Research in Science and Technological Education 24 (1): 69-84
Section Developed by: Keith Ross, University of Gloucestershire
Published: 10 Oct 2005, Last Updated: 12 Sep 2008