1. Strengths and Weaknesses
Theory & Methods
Key Insights
Penner & Klahr, Child Development, 1996
The Interaction of Domain-Specific Knowledge and Domain-General Discovery Strategies: A Study with Sinking Objects
Subjects: 10, 12, 14 year-olds
Procedure:
1. Why do things sink? What makes things sink fast?
2. Experiment by dropping 1-2 objects in water
- objects vary in size, shape, weight, and material; all variables co-vary; cannot infer from single exp’t
3. What causes an object to sink fast?
Mean trial when 1st non-weight-based experiment conducted 10 12 14
Findings
Strengths and Weaknesses
Most children initially believe that weight alone affects sink rate, but after experimentation all the children learn that other attributes affect sink rate too
Older children are more likely to generate hypotheses
Older children are less likely to design experiments that demonstrate their pre-existing beliefs; they design experiments to test non-favored hypotheses
Children who find surprising results almost never follow them up with more experiments, and these results rarely change their beliefs
Strengths
Quantitative and qualitative data
Examined process data as well as outcomes
Well-designed task
In-depth analyses
Weaknesses/Questions
Perhaps domain-general prior knowledge is affecting the results here?
Need to expand this idea of domain-specific prior knowledge and domain-general skills
A deficit model
Small N (10 per age group)
Chose a domain where children would have significant prior knowledge: the sinking of objects
Knew from an initial pilot study that most children believe that weight is the only factor affecting sink rate.
The sinking velocity is dependent on the gravitational force on the object (which depends on weight or mass), the opposing forces of friction and buoyancy. Friction depends on surface texture of the material, size, cross-sectional area. Buoyant force on the ball depends on the density, which is essentially a ratio of weight to size.
Put them in a situation where they would need to undergo the whole scientific process: hypothesizing, designing experiments, testing, interpreting the results. More realistic, real-world situation, where variables are correlated (size and weight)
Analyzed the sequence of experiments chlldren did, their reasoning about it: hypotheses, predictions, conclusions
(e.g., children are used to varying only one attribute in an experiment)
prior knowledge gets in the way of understanding, rather than thinking of ways that prior knowledge can be helpful.