Yup, Grow is not only built on the latest psychological research, it’s also been tested in a longitudinal study with students building new learning habits (the paper is publicly available here). Did it work? Short answer: Yup. But check the stats yourself.
Around 100 students tested Grow for 6 weeks. They answered questions after each habit repetition that were then used to calculate different psychometric scores (range 1-10).
Automaticity shows how strong a habit has become. It increased considerably over the 42 habit repetitions.
Motivational interference is an indicator for how motivationally bulletproof the habit is. A low value means the habit is resistant to Netflix, your phone and other sources of procrastination. Check out this neat decrease!