Diadochokinetic rate (DDK) refers to an assessment tool, used by speech-language pathologists (SLPs), that measures how quickly an individual can accurately produce a series of rapid, alternating sounds. These sounds, also called tokens, may be one syllable such as "puh," two or three syllables such as "puh-tuh" or "puh-tuh-kuh," or familiar words such as "pattycake" or "buttercup." Other names for DDK rate include maximum repetition rate and The Fletcher Time-by-Count Test of Diadochokinetic Syllable Rate, the latter of which is named for the clinician who published DKK rate data in 1972.
Diadochokinetic rate is one means of assessing oral motor skills. DDK rate provides information about a person's ability to make rapid speech movements using different parts of his mouth. For example, the sounds "puh," "tuh," and "kuh" use the front (the lips), middle (the tip of the tongue), and back of the mouth (the soft palate), respectively. Evaluation of diadochokinetic rate usually occurs as part of an oral motor skills assessment. Other aspects of an oral motor skills assessment include examination of oral facial structures (lips, tongue, jaw, teeth, palate, and pharynx) and evaluation of velopharangeal function and breathing.
In general, DDK rates increase as children age and their motor systems mature. Some studies have shown reduced DDK rates in children and adults with speech impairments when compared to rates for individuals with typical speech. Examples of conditions that may be associated with a slower or more variable DDK rate include ataxia , dysarthria , childhood apraxia of speech, and stuttering .
The task of measuring DDK rate usually occurs in a single session and takes as little as 15–20 minutes for the SLP to administer and score. Prior to administering the test, the speech-language pathologist will demonstrate the sound(s) to be repeated and allow the patient to complete several practice trials. A trial is defined by a predetermined amount of time or number of repetitions. Generally, the SLP will administer a series of tests, each of which requires the client to produce a different sound or combination of sounds.
To measure the DDK rate, a SLP will record how many times the individual repeats the sound or combination of sounds in a given period of time (usually five to 15 seconds). DDK rates are measured in terms of iterations per second (it/s) or in terms of the time required to produce a certain number of iterations of a mono-, bi-, or trisyllabic token. The rate will be calculated and compared to the published norms. The SLP may use specialized recording equipment and a computer software program to record and analyze DDK rate. The DDK rate is calculated by dividing the total number of iterations by the duration of the trial or by determining the time it took the client to make a set number of iterations. The results are scored and compared to the published normative values. For example, in the data published by Fletcher (1972), the norm for 20 repetitions of the syllable "puh" for a child at age 10 is 3.7 seconds.
Some clients, especially preschool age children, may have difficulty complying with the instructions or completing the DDK tasks. In such cases, real words such as "buttercup," or "pattycake" may be used to test diadochokinetic rate. Also, preliminary findings from research published by Yaruss and Logan in 2002 indicate that other means of assessing DDK productions in young children, namely, measurement of accuracy and fluency, may be more useful diagnostic tools than standard measures of DDK rate.
Fletcher, S. G. "Time-by-Count Measurement of Diadochokinetic Syllable Rate." Journal of Speech and Hearing Research 15 (Dec 1972): 763–70.
Yaruss, J. S., and K. Logan. "Evaluating Rate, Accuracy, and Fluency of Young Children's Diadochokinetic Productions: A Preliminary Investigation." Journal of Fluency Disorders 27 (2002): 65–86.
Williams, P., and J. Stackhouse. "Diadochokinetic Skills: Normal and Atypical Performance in Children Aged 3–5 Years." International Journal of Language and Communication Disorders 33 (Suppl 1998): 481–6.
Apraxia Kids home page. (May 30, 2004). <http://www.apraxia-kids.org/index.html>.
Dawn J. Cardeiro, MS, CGC