Using Analogies to Teach about Time
Guiding Principles for Teaching with Analogies
Analogy refers to relating two different concepts based on shared features. The two concepts are referred to as the base and the target. The base concept is the one that is already familiar. The target concept is the one we want to learn about. Used well, analogies can be excellent teaching tools; used poorly, they may be of little use and can even introduce misconceptions. Based on research on the use of analogies in teaching (see references) we recommend the following guidelines for the use of analogies in teaching about time:
- Make it clear that you are making an analogy and what the analogy represents.
- Choose your analogies carefully.
- The base and target concepts should be structurally aligned (similar to each other in as many ways as possible) so that students are not confused or distracted by the ways that they differ.
- The base concept needs to be familiar to students. For example, if we make an analogy between plumbing systems and the veins and arteries in our bodies, the analogy will only work well if students are familiar with plumbing systems.
- The analogy you are using might have pre-exisitng functional, spatial, or emotional characteristics that can interfere with making the analogy. For example, if your analogy involves a calendar, students may expect your target concept to be divided into equal temporal units, just like a calendar. As another example, if an analogy involves talking about money, students may become distracted by feelings about their own finances.
- Point out the ways in which the target and base are different so that students don't develop misconceptions. For example, pipes are rigid but our veins/arteries are not. Contrasting the target and base can be a way to highlight important features of the target.
- If the target and base concepts are not very similar, you can use "progressive alignment" to make small steps from the base to the target. Progressive alignment (Kotovsky and Gentner, 1996) starts by making an analogy between two highly similar items (the base concept and an intermediate concept), then continues by mapping from the intermediate concept to the target concept. You may need to make several steps depending on how dissimilar the target and base are. For example:
- Thompson and Opfer (2010) asked children to find the midpoint on a numberline that spanned 1-10. This was used as first step in having them choose the midpoint on a numberline that spanned 1-100.
- The teaching activity Hierarchical Alignment of Timelines moves students from mapping their own lives onto a meter to mapping geologic time onto a meter, using several intermediate time spans.
- Give students multiple opportunities to practice using the analogy, mapping the target concept onto the base concept.
Common Analogies for Time
There are many common analogies used for representing the Geologic Timescale and the expanse of time. Our goal here is to discuss a few of these analogies in the context of the guiding principles listed above. Please note that the strengths and weaknesses described here may or may not be relevant to the specific way you use the analogy in your class. Moveover, many of the weaknesses described here can be addressed by pointing them out to students (where the target concept differs from the base concept) and by using progressive alignment (where the scales of the base and target concepts are vastly different).
Analogies that map time onto other magnitudes of time
Examples: day, year, clapping (once/second represents one year: Clary and Wandersee, 2009)
- The base concept is familiar.
- The difference in scale between the base and target concept may be so large that structural alignment is difficult. Mapping 4,600,000,000 years onto one year or one day is cognitively non-trivial.
- Many temporal units (days, years) have unrelated functional features that may mislead or distract students. For example, the equal divisions of days into hours, minutes and seconds may lead students to expect similar regular divisions throughout geologic time.
Analogies that map time onto distance
- Students can (in most cases) see and (in some cases) manipulate the base concept.
- String and clothesline have no pre-existing spatial characteristics.
- Many of these base concepts have pre-existing spatial and/or functional characteristics.
- The base concept can be an unfamiliar magnitude. (Just how long is a roll of toilet paper? A trip across the country?)
- Practical constraints like classroom size could necessitate bending the string/toilet paper/etc. This is likely to interfere with alignment because it makes it difficult to "see" the length of the base concept.
- The difference in scale between the base and target concept may be so large that structural alignment is difficult. For example, the smallest perceivable fraction of the length of a string across the classroom may still represent an unfathomably long period of time for your students (Parker, 2011). On a 20-meter long string representing the Earth's history, 1 millimeter represents 230,000 years.
Analogies that map time onto spaces or volumes
Examples: Mapping geologic time onto the Eiffel Tower, the Washington Monument, a football field, a swimming pool
- Could motivate students if they know the base concept and it's something they find interesting.
- The base concept can be an unfamiliar magnitude. (How tall is the Eiffel Tower? How well can your students visualize that distance?)
- There may be unrelated features on the pre-existing space that distract or confuse students. For example, the regular markings on a football field may lead students to expect similar regular divisions throughout geologic time.
Assessing Student Understanding of Analogies
Assessing whether students understand the analogies you are using is critically important: if they don't understand the analogy, they won't understand the target concept. Assessment can be built into the analogy activity, and can focus on parts of the analogy (or the intermediate steps in progressive alignment) that you expect to be challenging. Possible assessment could include:
- Low or no stakes quiz questions, such as ConcepTests or Classroom Response System (clicker) questions.
- Brief small group discussions comparing target and base concepts.
- Having students develop their own analogy for the same target concept.
- Student reflection (e.g., engaging students in metacognition about what they have learned). This can serve both as an assessment activity and as a reinforcement of the learning.
To choose an assessment activity or activities, consider what you want to achieve:
- Do you want immediate feedback on how well students understand the analogy?
- Do you want students to get immediate feedback on how well they understand the analogy? (Research shows that timely feedback facilitates and strengthens learning.)
- Do you have any concerns about the analogy leading to student misconceptions about the target concept?
- Do you want to know whether and how well students can apply what they've learned?
- Do you want to know how well students retain the analogy and their understanding of the target concept after a day, a week, or a month?
By carefully considering your (and your students') needs, you can select appropriate assessment methods to meet those needs. For example, if you want your or your students to get immediate feedback on how well they understand the analogy, you could use ConcepTest or Classroom Response System (clicker) questions, small group discussions, or written student reflections the day you introduce the analogy. If you want to know how well students understand the target concept, you could ask them to develop their own analogy for it. If you want to know how well they retain their understanding, an exam question later in the term may be more appropriate.
Clary and Wandersee (2009). How old? Tested and trouble-free ways to convey geologic time. Science Scope, Dec. 2009, p. 62-66.
Jee, Uttal, Gentner, Manduca, Shipley, Sageman, Ormand, & Tikoff (2010). Analogical thinking in geoscience education. Journal of Geoscience Education, 58 (1), 2-13.
Kotovsky and Gentner (1996). Comparison and categorization in the development of relational similarity. Child Development, 67, 2797-2822.
Parker, J. D. (2011). Using Google Earth to Teach the Magnitude of Deep Time. Journal of College Science Teaching, 40 (5), 23-27.
Thompson and Opfer (2010). How 15 hundred is like 15 cherries: Effect of progressive alignment on representational changes in numerical cognition. Child Development, 81 (6), 1768-1786.