Chapter 6, page 107
energy production in power plants to the process of energy production in mitochondria. Mapping means
that ideas from one situation are placed in correspondence with related idea from the other situation. For
example:
Ɣ The idea that there are inputs to a power plant (natural gas and oxygen) is mapped to the idea that
there are inputs to the process of respiration in mitochondria (glucose and oxygen). The particular
inputs are different, but both power plants and mitochondria have inputs.
Ɣ The idea that there are outputs from a power plant (energy, water, and carbon dioxide) is mapped to
the idea that there are outputs from the process of respiration in mitochondria (energy, water, and
carbon dioxide). Unlike with the inputs, this time the outputs are the same in the two processes.
Ɣ The idea that energy production occurs inside the power plant is mapped to the idea that energy
production occurs inside the mitochondrion.
Some elements must be changed during the mapping. For example, “natural gas” is used as an input in
some power plants, but the corresponding input in cellular energy production is glucose.
When using analogies, there is a danger that students may map ideas incorrectly so that the analogy
causes students to form alternative conceptions. For example, students learning about the power plant-
mitochondria analogy might mistakenly map these ideas.
Ɣ The idea that power plants also release pollution into the air and water might mistakenly be mapped to
mitochondria, yielding the idea that mitochondria release pollution into the cell. This would be an error,
because there is no counterpart to pollution production in the activities of mitochondria.
Thus, it is important to help students make correct mappings and avoid incorrect mappings when using
analogies (Glynn, 2007).
Problem 6.6 Designing instruction.When students of any age are learning to write persuasive essays, they
typically fail to consider arguments against their position. Students have a real
bias against thinking about the other side of a question. For example, a student
may write, “Schools should not be held all year round because students need a
break so that they can relax” without thinking about counterarguments such as
“Students forget a lot over the summer when they get the summer off, and
this slows their learning down.” How can teachers encourage students to
consider counterarguments when writing persuasive essays? What conceptual
resource can teachers draw on?Response: There are many possible responses to this question. The response
here was provided by a middle-school teacher I have worked with in recent
research. This teacher identified a conceptual resource in students’ personal
experiences. She noticed that even though her students seldom considered
counterarguments when they wrote essays, there was one context in which
her students did regularly consider counterarguments: when they were trying
to persuade their parents to give them permission to do something such as
sleep at a friend’s house. In this situation in their everyday lives, students
regularly anticipate their parents’ counterarguments and take their parents’
counterarguments into account when they make their arguments. For
example, when they argue that their parents should let them sleep over at a
friend’s house, they anticipate their parents’ potential counterarguments
(“you can’t sleep over because you have to get up early tomorrow morning”)
and try to undermine these potential counterarguments in their own
arguments (“If you let us go, we promise to go to bed early!”). In this way,