Working (or 'short-term') memory capacity is a strong predictor of success in language development. That is because exposure to language, whether wild or instructed, may be more or less effective in proportion to memory capacity, through (1) retention of words and (2) holding sets of words together in phrases and sentences long enough for representations to be established in permanent memory. This capacity is not fixed but rather subject to expansion through strategy and practice. Here are two STM instruments with research support that have featured in applied and psycholinguistics studies.

1. Phonological STM v.09 (2020)

In a 'serial recognition task,' learners listen to a string of words or non-words delivered by TTS (text to speech) and try to recall them in the same order. Number and type of items can be varied.

(TTS does not work on iPhone) <== NO LONGER TRUE - FEASIBILITY STUDY IN PROGRESS ON THIS...

2. Text STM v.0.9 (2020)

Users see a list of words, which disappears and they try to recall them from a re-ordered list with distractors. Number and frequency of items can be varied. (A version of Kim's Game)

Service & Kohonen (1995) Phonological memory & vocabulary
Hummel & French (2010) PM & L2 classroom
Hummel & French (2016) PM & L2 proficiency