Causality still gives rise to debate among scientists and philosophers.
Research in science education has shown a strong presence in common reasoning of causal explanations, often conceived as a linear, logical and chronological sequence of causes and effects. Some researchers have proposed to use this common causal reasoning as a basis for teaching sequences in electricity.
This paper analyses some features of causal reasoning in physics, based on a study conducted using questionnaires and interviews involving students and teachers. This study has shown:
- a confusion between efficient and contingent causes, between the conditions of occurrence of a phenomenon and the cause actually producing it;
- a tendency to “displace” causes, skipping intermediate objects;
- a difficulty in connecting local causes and global effects.
For example, 94% of 46 students and 36 teachers (in initial or in-service training) asked which of the four fundamental types of force (gravitational, electromagnetic, strong or weak) a swimmer feels on his eardrums, when deep under water, answered that it is a gravitational force. The justifications confirm a shift in meaning of the role of gravity: pressure is related to weight, it is due to it, gravity causes, creates pressure, the pressing force is the gravity force.
In a situation in which two blocks were placed one upon the other and one of them was pulled by exerting a force on it, many students considered that this force acted also on the other block, thus “displacing” the cause of movement beyond the first block. A similar type of reasoning is observed in other situations.
In recorded discussions on pressure and forces inside a container filled with water, students show their difficulty in connecting the global rules or formulas asserting that things must be so, with a local causal reasoning, based on what occurs in a given spot of fluid.
The paper will discuss various epistemological views about causality, the relation of common and scientific causal reasoning and provide some suggestions for teaching.