The Analogy Card Split: Settling Three Disagreements With a Reusable Rule
Four students in a fifth-grade reasoning group are working through a stack of analogy and classification cards, and they have split on three of them. Card one reads thermometer : temperature :: scale : ___, with the choices weight, heavy, balance, and measure. Jonas picks heavy, arguing that a scale is what you use to find out how heavy something is. Priya picks weight and says the two halves of the pair have to match in kind, not merely in topic. Card two reads puppy : dog :: sapling : ___, with the choices tree, plant, forest, and leaf. Marcus picks plant because a sapling really is a plant; Tessa picks tree. Card three is a classification item whose four words are hammer, saw, drill, nail. Devon wants to cross out drill because it runs on electricity while the others are hand tools. The teacher asks you to settle each disagreement with a rule the students can carry to the next card, rather than by announcing an answer key.
1. Settle the thermometer card. Which choice is defensible, and what single test decides between weight and heavy?
Read the worked answer
Weight is the defensible choice.
The first pair joins an instrument to the quantity that instrument reports: a thermometer reports temperature. The second term in each pair is a noun naming a measurable quantity, so the blank must name a quantity too.
Apply the kind test to each option:
- weight - a noun naming the quantity a scale reports. Kind matches temperature. Fits.
- heavy - an adjective describing an object, not a quantity. It answers the topic question but breaks the parallel.
- balance - another instrument, which would sit in the first slot, not the second.
- measure - a verb or a general act, not a named quantity.
Jonas matched the topic; Priya matched the kind. The reusable test: say the pair as a sentence in both directions and check that the second word plays the same grammatical and conceptual role in both halves. If one half names a thing and the other describes a quality, the pair is broken no matter how sensible it sounds.
2. Settle the puppy card, and explain what separates tree from plant even though Marcus's statement is true.
Read the worked answer
Tree is the better answer.
The relationship is young form to mature form of the same kind of living thing: a puppy grows into a dog, a sapling grows into a tree. The second word must name what the first thing becomes.
Marcus's objection is factually correct but at the wrong level. A sapling is a plant, and a puppy is an animal, so plant would only work if the first pair were puppy : animal, which it is not. Plant catches category membership and throws away the growing-up relationship that the first pair supplies.
Two useful checks follow. First, swap the pair around: tree to sapling works as adult to young, and so does dog to puppy; plant to sapling does not carry the same meaning. Second, prefer the answer that keeps the specificity of the given pair. When a broader word is also true, it is usually the trap, because a broader word makes many answers defensible and the item would then have no single best choice.
3. Settle the classification card. Devon's observation about electricity is accurate, so why does nail still win?
Read the worked answer
Nail is the word that does not belong.
The decisive test in a classification item is not whether the odd word has a difference - every word has some difference - but whether removing it leaves the other three as tight and uniform a set as possible.
- Remove nail: hammer, saw, drill are all tools that act on building materials. Tight set.
- Remove drill: hammer, saw, nail leaves two tools plus the fastener the tools drive. Not uniform.
Devon's power-source rule does split the list, but it leaves a mixed set, so it explains less of the card. His objection is a real property of the drill, just a property that generates a weaker grouping.
The reusable rule: try each candidate removal, then ask which remaining trio can be described in one short sentence with no leftover exceptions. The reading that needs the fewest qualifiers is the intended one. Also check the level of the category - tools versus objects used in building - because a switch in level is a common way to make a wrong odd word look reasonable.