Fluency

SSI-4: What It Measures

Stuttering Severity Instrument, Fourth Edition

Quick answer

The SSI-4 measures observable stuttering severity by scoring three dimensions from recorded speech samples: frequency of stuttered syllables, average duration of the three longest stuttering events, and physical concomitants such as facial grimaces or head movements. The three scores combine into a total that maps to a severity rating from very mild to very severe.

The SSI-4 is the standard quantification of visible stuttering. It is deliberately narrow: three observable dimensions, scored from recordings, converted to a severity rating. That narrowness is why it belongs next to an impact measure rather than alone.

SSI-4 at a glance

Full name: Stuttering Severity Instrument, Fourth Edition
Publisher: PRO-ED
Domain: Fluency
Age range: Preschool through adult (readers and nonreaders)
Administration time: About 20–30 minutes including sample collection
Format: Observational measure scored from recorded speech samples
Score types: Frequency score, Duration score, Physical concomitants score, Total overall score, Severity rating and percentile

What the SSI-4 measures

Frequency: percentage of syllables stuttered in speaking and reading tasks
Duration: average length of the three longest stuttering events, timed to tenths of a second
Physical concomitants: distracting sounds, facial grimaces, head movements, and extremity movements rated 0–5
Naturalness ratings and self-report supplements

Subtests and sections

Speaking task: Conversational sample of at least 200 syllables, recorded for later scoring.
Reading task: Passage reading for readers; a second picture-based speaking task substitutes for nonreaders.
Frequency scoring: Stuttered syllables converted to a percentage and then to a task score.
Duration scoring: The three longest stuttering events timed and averaged.
Physical Concomitants scale: Four categories rated on a 0–5 scale of distraction to the listener.

Stuttering-like vs. typical disfluencies

Accurate SSI-4 scoring depends on counting the right events. Stuttering-like disfluencies include monosyllabic whole-word repetitions, part-word or sound repetitions, sound prolongations, and blocks. Typical or other disfluencies include interjections ('um'), phrase repetitions, and revisions, which occur in all speakers and are not counted as stuttering.

Preschool differential diagnosis rests on this distinction plus risk factors: family history, time since onset, sex, concomitant speech-language concerns, and the child's and family's reactions. A 3-year-old with mostly revisions and interjections is typically disfluent; the same child with frequent blocks, prolongations, and visible tension warrants monitoring or intervention.

Getting a representative sample

Stuttering varies by context, listener, fatigue, and task demand. A clinic-room conversation with a familiar SLP can underrepresent classroom or telephone stuttering by a wide margin. Recording samples in more than one setting, or collecting a home recording from the family, improves representativeness and defends the severity rating you report.

Strengths

Objective, replicable severity index suitable for progress monitoring.
Separate protocols for readers and nonreaders extend the age range downward.
Recording-based scoring supports reliability checks and second-rater agreement.
Widely referenced in fluency research, so results are comparable.

Limitations

Says nothing about avoidance, anxiety, or participation — the covert iceberg.
Single-session samples may not represent variable stuttering across contexts.
Physical concomitant ratings involve clinician judgment and can drift without reliability checks.
Severity change is not the same as therapy success for many older clients.

When clinicians use it

Baseline and outcome measurement of observable stuttering.
Eligibility documentation when districts require a standardized fluency score.
Reliability training for graduate clinicians learning disfluency counting.
Pairing with the OASES for a complete ICF-aligned fluency evaluation.

What the Praxis 5331 asks about the SSI-4

Know the three scored dimensions cold — frequency, duration, physical concomitants.
Distinguish stuttering-like disfluencies (part-word repetitions, prolongations, blocks) from typical disfluencies (interjections, revisions, phrase repetitions).
Expect items requiring both a severity measure and an impact measure for an adequate evaluation.

Practice assessment questions with rationales

Praxis Path pairs this reference material with scenario questions, spaced-repetition flashcards, and a timed 132-question mock exam.

See what's included Try a free practice test

FAQ

What does the SSI-4 measure?

Observable stuttering severity across three dimensions — frequency of stuttered syllables, duration of the longest stuttering events, and physical concomitants — combined into a severity rating.

Can the SSI-4 be used with nonreaders?

Yes. Nonreaders complete a second picture-based speaking task in place of the reading passage.

How many syllables are needed for an SSI-4 sample?

At least 200 syllables per task is the standard target so the frequency percentage is stable.

Should the SSI-4 be used alone?

No. Best practice pairs it with an impact measure such as the OASES because severity and life impact are only loosely correlated.