While the Phrasing Method has not been directly studied, it's largely based on well studied academic principles:

Spaced Repetition. This technique uses increasing intervals between reviews to strengthen long-term memory, backed by over a century of research showing its effectiveness. Phrasing automates the spacing of reviews using a battle-tested algorithm to ensure you remember everything you've learned with minimal daily effort.

Effortful Retrieval. The act of actively recalling information (rather than passively reviewing it) creates stronger memory formation. Phrasing's review system is designed around active recall, requiring you to retrieve words and meanings rather than simply recognizing them. We don't shy away from difficulty because it 'hurts engagement', but instead lean in because it improves results.

The Affective Filter Hypothesis. This theory states that stress, anxiety, and negative emotions create a mental barrier that blocks language acquisition. Phrasing prioritizes enjoyment and stress-free reviews through its beautiful interface and it's Humane SRS, which treats user psychology as a first-class citizen, keeping your affective filter low.

The Zone of Proximal Development. Learning is most effective when material is just beyond your current level—challenging but not overwhelming. Phrasing's Humane SRS adapts to your every review, making sure you're always in the Zone of Proximal Development.

Contextualized Learning. Words and grammar learned within meaningful sentences are better retained and more readily applied than isolated vocabulary or rules. Contouring emphasizes learning words embedded in full, complex sentences rather than as isolated vocabulary items.

Tolerance of Ambiguity. Successful language learners can comfortably encounter unfamiliar elements without anxiety or the need for immediate clarity. Contouring trains this tolerance by deliberately having you work with sentences where you only understand some words, getting comfortable with not understanding everything at once.

Category Induction. This refers to the brain's innate ability to deduce grammatical patterns (like word order or verb forms) from natural examples without explicit instruction. Contouring exposes you to authentic sentence patterns repeatedly, allowing your brain to unconsciously recognize grammatical categories from distributional cues, aided by the interactive nature of Phrasing's interface.

Interleaving. Mixing different topics during study (rather than blocking them into separate themed units) improves long-term retention and transfer of knowledge. Most language methods will segment learning into broad units and themes, which is substantially less effective for learning, recall, and applicability (ability to use and recall in context).

The Input Hypothesis. This theory states that language acquisition occurs through exposure to comprehensible input slightly above your current level. Phrasing makes any sentence comprehensible, and it's focus on fully complex sentences ensure there is always something just above your current level.

Extensive Reading. Voluntary exposure to large quantities of interesting, comprehensible text drives language acquisition more effectively than drilling exercises. Contouring mimics extensive reading by having you accumulate and work through many authentic sentences over time, building exposure to natural language patterns.

The Encoding Variability Hypothesis. Processing the same information through multiple formats (audio, visual, textual) creates diverse memory traces, making recall easier by providing multiple retrieval pathways. Phrasing reinforces each word through audio playback, text display, and visual segmentation on every review.

Contextual Variability. Encountering words in diverse situations builds richer understanding and more flexible usage than seeing them in limited contexts. Phrasing's Language Graph explicitly connects each word to all its appearances across different sentences, exposing you to varied contexts for every word you learn.