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PGU

Percent Grammatical Utterances (PGU)

PGU is the percentage of utterances in the sample that contain no morphosyntactic errors — the single best proxy for grammatical accuracy.

What PGU measures

Percent Grammatical Utterances, also known as Percent Correct Morphology in some protocols, is the proportion of utterances in a language sample that contain no errors in bound morphology or sentence structure. It is a simple accuracy measure: count the number of fully grammatical utterances, divide by the number of analyzable utterances, and report as a percentage. Eisenberg and colleagues reviewed the metric in 2001 and confirmed its sensitivity to developmental language disorder in preschool and early school-age children.

Formula

PGU = (grammatical utterances ÷ analyzable utterances) × 100

Normative ranges and benchmarks

  • Age 4;0 — PGU ≈ 80 – 90% in typical development
  • Age 6;0 — PGU ≈ 90 – 96%
  • Age 8;0 — PGU ≈ 95 – 98%
  • Children with DLD average 10 – 25 percentage points below age-matched peers
  • PGU under 85% in a kindergarten sample is a strong sensitivity marker for DLD

Normative bands are central estimates drawn from the cited literature. Individual variation is wide — always cross-reference against the source paper and your assessment's own manual before quoting a cut-score in a report.

Clinical use

PGU pairs naturally with MLU in a preschool report — MLU tells you how long the utterances are, PGU tells you how often they are correct. Together the two metrics discriminate typically developing from language-impaired children with impressive accuracy in the literature. Clinically, PGU is also useful as a progress-monitoring variable because small gains are visible over six-week chunks of therapy. The main coding decision is what counts as an "error" — dialectal variation should never be counted as ungrammatical, and the clinician should document the dialect features they excluded up front. For AAE or other dialect speakers, use the Diagnostic Evaluation of Language Variation (DELV) decision rules rather than a standard grammaticality code.

“PGU is the metric that separates "late talker" from "language disorder" at age 4. Length alone is noisy — length plus accuracy together is as close as LSA gets to a gold standard for DLD.”
Length plus accuracy is the real test

Free tools that compute PGU

PGU Calculator

Paste a language sample, tap G or U per utterance, and get Percent Grammatical Utterances (PGU) live. Returns the Eisenberg & Guo (2013) severity band (typical / borderline / clinical concern) once at least 25 utterances are scored. Mobile-friendly scoring table, client-side, no sign-up.

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MLU Calculator

Paste a language sample and get Mean Length of Utterance in morphemes and words, total utterances, total morphemes, and the matching Brown's stage. Implements Brown (1973) morpheme counting rules and runs entirely in your browser.

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Language Sample Worksheet

Free printable and fillable language sample analysis worksheet for speech-language pathologists. Five columns (utterance #, transcription, morpheme count, grammatical Y/N, notes), configurable row count up to 100 utterances, browser print produces a clean PDF, and an inline running summary tracks total utterances, total morphemes, and rolling MLU as you fill it in.

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Related LSA metrics

MLU-M

Mean Length of Utterance in Morphemes (MLU-M)

MLU-M is the average number of morphemes per utterance and remains the single most-used index of early grammatical development in English.

DSS

Developmental Sentence Score (DSS)

DSS assigns weighted point values to eight grammatical categories across a 50-utterance sample to produce a single age-sensitive score.

PCU

Percent Complex Utterances (PCU)

PCU is the share of a child’s utterances that contain two or more clauses — the clearest single marker of emerging syntactic complexity.

References

  1. Eisenberg, S. L., Fersko, T. M., & Lundgren, C. (2001). The use of MLU for identifying language impairment in preschool children: A review. AJSLP, 10(4), 323–342.
  2. Hadley, P. A., & Rice, M. L. (1996). Emergent uses of BE and DO: Evidence from children with specific language impairment. Language Acquisition, 5(3), 209–243.
  3. Oetting, J. B., Cleveland, L. H., & Cope, R. F. (2008). Empirically derived combinations of tools and clinical cutoffs. LSHSS, 39(1), 44–53.