ACT® · Science: Evaluating Scientific Arguments and Models with Evidence (8-13 items)
Similarities and Differences Between Competing Models (EMI 404)
Competing scientists almost always share the same data and the same big-picture frame; they usually split on one specific claim, like mechanism or timing, not on everything.
Two scientists looking at the same evidence rarely disagree from top to bottom. They're explaining the same observation, so they typically share the setup: what happened, roughly when, and that some cause is responsible. The real work in a model comparison question is finding the one premise where their explanations peel apart. Line up each model's claims piece by piece, agreed facts, timing, mechanism, outcome, and mark exactly which piece changes between them.
Do this by listing each scientist's statement as separate claims rather than reading the conclusion as one lump idea. Two models can arrive at the identical final number, like a glacier retreating a fixed amount per year, while disagreeing completely about why: one says warmer air melts the surface, the other says warmer water erodes the base from underneath. If you only compare their bottom-line conclusions, you'll miss that the real disagreement lives in the mechanism, not the outcome.
This skill connects to the broader work of this category: once you can isolate the exact point of disagreement, you can test each model against new evidence to see which one it supports. It also sets up mixed or third viewpoints, where a new scientist agrees with one model on cause and another on timing. That third view isn't a compromise; it's its own distinct model, built from pieces of both, and you locate it the same way: claim by claim.
Key terms
- Model
- A scientist's explanation built from a chain of claims that together account for an observation.
- Shared premise
- A claim both competing models accept, often the basic observation or frame they're both explaining.
- Point of divergence
- The single specific claim, such as mechanism or timing, where two models stop agreeing.
- Mechanism
- The process a model proposes to explain how a cause produces its effect.
- Hybrid viewpoint
- A third model that combines pieces of two existing models, such as one's cause with another's timing.
Watch it explained
- How it worksHow do you draw two models side by side and mark the single premise where they split apart?
- Worked exampleFind the shared claim when one scientist blames volcanoes for a mass extinction and another blames an asteroid.
- Common mistakeWhy isn't finding the difference between two models a matter of comparing their conclusions?
- Going furtherWhat changes when a third viewpoint agrees with one scientist on cause and the other on timing?
Check yourself
End of topic.