Our hypothesis in one chain
Our founding idea rests on three links:
- Vocabulary → reading comprehension. Well established.
- Language → math word problems. Supported by research.
- Studying targeted vocabulary → higher SAT scores. The link we're testing.
Link 1: Vocabulary and reading comprehension go together
The relationship between vocabulary knowledge and reading comprehension is one of the most replicated findings in reading research. For example, one large meta-analysis of more than 100 studies (276 effect sizes, almost 21,000 learners) found a correlation of about 0.57 between vocabulary knowledge and reading comprehension, or roughly 0.56–0.67 after correcting for measurement error. That means vocabulary accounted for roughly 31–45% of the variation in comprehension. That analysis studied second-language learners. The link is also well documented for native English speakers.
Source: Zhang & Zhang (2022) [1].
Link 2: Language skills matter in math, too
Math word problems are, in part, a reading task. Studies of younger students have found that language comprehension predicts word-problem solving separately from arithmetic skill.
Sources: Fuchs et al. (2015) [2]; Fuchs et al. (2018) [3].
This matches what our founder saw across two decades of tutoring. Students who arrived with strong vocabularies tended to do better on both sections of the SAT, not just Reading and Writing. We didn't see the same spillover from students who arrived strong in algebra or grammar.
Link 3: Where vocabulary study usually falls short, and why we built SATShield this way
A well-known meta-analysis of 37 vocabulary interventions found solid effects on tests built around the words that were taught (effect size d = 0.50), but much weaker effects on standardized tests (d = 0.10).
Source: Elleman, Lindo, Morphy & Compton (2009) [4].
Why the gap? Most vocabulary programs teach words A, B and C, then hope scores rise on a test full of unpredictable words X, Y and Z. Vocabulary instruction mostly helps with the words actually taught.
That's precisely the problem SATShield was designed around. Instead of hoping for transfer, we built the list from official practice tests to target the words most likely to be on this test, and we teach them in the test's own formats. It's the condition where the measured effect was five times larger.
Also worth noting: in that same meta-analysis, students with reading difficulties gained more than three times as much as students without them (d = 1.23 vs. 0.39, on custom measures). The students who need the most help may stand to gain the most.
The learning science under the app
| Principle | What it says | How SATShield uses it |
|---|---|---|
| The forgetting curve | Memory fades fastest right after learning, then more slowly | Reviews are scheduled just before a word would slip |
| Spaced practice | Spreading practice over time beats cramming for long-term retention | Growing review intervals (about 2 → 4 → 8 → 17 → 36 days) |
| Retrieval practice | Pulling information out of memory strengthens it more than re-reading | Every level is a retrieval task, never just a re-read |
| The generation effect | Information you produce yourself is remembered better than information you select | Level 5: write your own sentence |
Sources: Ebbinghaus (1885) [5]; Cepeda et al. (2006) [6]; Roediger & Karpicke (2006) [7]; Slamecka & Graf (1978) [8].
What's not proven yet
How we're testing it: a pilot with tutors and students, using a delayed test 30 days after the last session (because durable memory is the whole claim) with real SAT-style questions. Over the longer term, we hope to follow students who start early all the way to an actual SAT sitting. We'll publish what we learn here, whichever way it goes.
The floor
Even if the bigger hypothesis doesn't hold, a student who finishes SATShield walks into the test:
- knowing the words most likely to appear on it,
- recognizing the question formats on sight,
- reading punctuation as a signal, not decoration,
- with a daily study habit, built from time that used to go to scrolling.
None of that depends on a theory being right. The upside is what we're testing. The baseline is already worth it.
Sources
- Zhang, S., & Zhang, X. (2022). The relationship between vocabulary knowledge and L2 reading/listening comprehension: A meta-analysis. Language Teaching Research, 26(4). doi.org/10.1177/1362168820913998 (opens in a new tab)
- Fuchs, L. S., Fuchs, D., Compton, D. L., Hamlett, C. L., & Wang, A. Y. (2015). Is word-problem solving a form of text comprehension? Scientific Studies of Reading, 19(3), 204–223. eric.ed.gov/?id=EJ1055941 (opens in a new tab)
- Fuchs, L. S., et al. (2018). Text comprehension and oral language as predictors of word-problem solving: Insights into word-problem solving as a form of text comprehension. Scientific Studies of Reading, 22(2). eric.ed.gov/?id=EJ1168256 (opens in a new tab)
- Elleman, A. M., Lindo, E. J., Morphy, P., & Compton, D. L. (2009). The impact of vocabulary instruction on passage-level comprehension of school-age children: A meta-analysis. Journal of Research on Educational Effectiveness, 2(1), 1–44. doi.org/10.1080/19345740802539200 (opens in a new tab)
- Ebbinghaus, H. (1885/1913). Memory: A Contribution to Experimental Psychology.
- Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354–380.
- Roediger, H. L., & Karpicke, J. D. (2006). Test-enhanced learning: Taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255.
- Slamecka, N. J., & Graf, P. (1978). The generation effect: Delineation of a phenomenon. Journal of Experimental Psychology: Human Learning and Memory, 4(6), 592–604.