SAT Inferences
Draw the conclusion the passage's evidence logically forces.
How to score it
- The blank usually follows “therefore / thus / suggests that” — the answer is the conclusion the evidence guarantees.
- Stay inside the evidence: pick what must be true, not what could be true.
- Map the logical chain; on hard items it's two or three steps.
Common traps
- Over-reach — a stronger claim than the evidence supports.
- Reasonable-sounding but introduces a new idea the text never gave you.
- Reverses the direction of the logic.
The 2 question types, with real examples
Logically complete the text
“Which choice most logically completes the text?”
Neuroscientist Amanda Wong studied how the brain processes unexpected rewards by monitoring neural activity in rats when they received food rewards that were larger than anticipated. She found that dopamine neurons showed increased activity specifically when rewards exceeded expectations, but showed little change when rewards matched expectations. Previous theories had proposed that dopamine neurons signaled the presence of any reward, but Wong's findings _____
Which choice most logically completes the text?
- Aestablish that all dopamine neurons in the brain respond identically to unexpected events.
- Bshow that dopamine neurons were more active when rats received larger rewards than expected.
- Cindicate that dopamine neuron activity may reflect reward prediction errors rather than reward presence alone.✓
- Dreveal how the size of food rewards affects overall neural activity throughout the rat brain.
The passage shows dopamine neurons respond to rewards exceeding expectations but not to expected rewards, logically implying they signal prediction errors rather than simply reward presence.
Must-be-true inference
“Based on the text, which statement must be true?”
In the early 1900s, botanist Agnes Arber studied the morphology of aquatic plants, focusing on how their structures adapted to underwater environments. She observed that many submerged species had divided leaves with thin segments, which she hypothesized increased surface area for gas exchange. Arber's detailed anatomical drawings revealed that these leaf modifications were consistent across multiple plant families, suggesting that similar environmental pressures led to comparable structural solutions in unrelated species.
Based on the text, which statement must be true?
- AArber proved that increased surface area is the primary evolutionary advantage of divided leaves in aquatic plants.
- BArber observed leaf modifications that appeared in multiple plant families living in similar environments.✓
- CArber was the first scientist to study the anatomy of aquatic plants.
- DArber's anatomical drawings were published in the early 1900s.
The text states that Arber's drawings revealed leaf modifications that were consistent across multiple plant families, which directly supports that she observed these modifications in multiple families in similar environments.
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