Table 1.

Productivity measures as defined by MacWhinney (2017).

Measure	Description
Duration	Total time of the sample in hours: minutes: seconds.
Total utterances	Includes all utterances used in computing MLU, plus unintelligible utterances (unintelligible); excludes non word utterances, for example a gesture only.
FREQ tokens aka Total Words	Total words tokens. Does not include repetitions and revisions.
Words per minute	FREQ tokens/duration converted to minutes
Propositional idea density	This measure was adapted from CPIDR3 (Computerized Propositional Idea Density Rater, third major version) CPIDR replicates Turner and Greene's rules (1977) for extracting propositions from text, based on the theory of Kintsch (1974) and the work of Snowdon et al. (1996) who showed that propositional idea density can be approximated by the number of verbs, adjectives, adverbs, prepositions, and conjunctions divided by the total number of words.
Retracing: retracing [//]:	Number of retracings (self-corrections or changes).
Disfluency index	Number of filled pauses, false starts revisions, repetitions divided by total no. of utterances.

Note. MLU = mean length of utterance the number of morphemes (units of linguistic meaning) divided by number of utterances.