Children with childhood apraxia of speech (CAS) are frequently noted in the literature as having disordered prosody. Prosody refers to intonation, stress pattern, loudness variations, pausing, and rhythm. We express prosody mainly by varying pitch, loudness, and duration. We also may use greater articulatory force to emphasize a word or phrase. Children with CAS are frequently reported to have prosodic errors as well as many speech sound errors. Often, these prosodic errors and articulation errors are thought of as two separate entities. The purpose of this article is to highlight potential relationships between speech characteristics of CAS, as well as the efforts to improve speech sound accuracy, and their impact on prosody.
Children with CAS have been reported to sound:
- robotic-like, producing each syllable one at a time and with equal stress
- aprosodic (i.e., decreased intonation patterns, monotone)
- dysprosodic (i.e., using prosody that doesnt match the expected intonation pattern)
- slow and choppy
- too fast
English-speaking children with CAS have also been observed to use word stress patterns that are similar to children younger than they are who are developing typically (i.e., 2-4 years of age). More specifically, children with CAS are more successful producing words with a strong-weak stress pattern (e.g., baby) than a weak-strong stress pattern (e.g., guitar). Children with CAS may have more success with strong-weak stress pattern words because one; they have had more practice with them and two; they may be easier to produce.
However, as previously mentioned, children with CAS frequently produce other types of prosodic errors, as well. When considering the types of sound errors children with CAS typically make, it is easy to see why we perceive disordered prosody. If we think about the effort required for correct articulation, it is also makes sense that prosody suffers. The following table summarizes common speech characteristics or errors of CAS and how they interact with prosody.
Table 1. Effects of CAS Speech Characteristics on Prosody
|Speech Characteristic/Error||Example||Potential Effect on Prosody|
|Deleting weak syllables||Child says ‘nana’ for ‘banana’ or ‘tar’ for ‘guitar‘||Deletion of weak syllables will leave a phrase with each syllable equally stressed. The normal stress pattern in sentences is to have an alternation between strong and weak syllables.|
|Vowel errors, such as tense/lax or lax/tense vowels, or vowelization of syllablic consonants||Child says ‘baba’ for ‘baby’ or ‘lito’ for ‘little’||Lexical stress errors.|
|Omissions (leaving out sounds)||‘un’ for ‘sun’; awewi’ for ‘strawberry’||Increased rate of speech|
|Substitution of glottal stops for other consonants||/?en ?i ?o ?om for “When do we go home?”||choppy|
|poor intelligibility||“I-awa-a-mo” for “I want to go home.”||Perception of increased rate of speech (similar effect as when listening to someone who speaks a different language)|
|increased effort on sequencing movement for speech||“I – want – to – go – now.”||Decreased rate and sounding robotic by producing one syllable at a time.|
In addition to articulatory effort and speech errors interfering with prosody, there is also the aspect of speech development to consider. Children with CAS are often characterized as having been quiet babies. Children who were quiet and did not babble missed the opportunity to practice/achieve rhythmic organization through babbling. Babbling provides the opportunity to organize phonation, articulation and respiration in a rhythmic style as evidenced by the childs prosody when vocalizing.
There are also several effects that speech therapy can have on prosody, not all of them positive. Many techniques speech therapists use promote correct articulation at the expense of natural sounding prosody. The following table summarizes common therapy techniques and their effect on prosody.
Table 2. Potential effects of therapy on prosody
|Therapy Target||Example||Effect on Prosody|
|sound (s) being targeted are overemphasized||“Tell me ‘errrr’ now tell me teacher“||Misplaced word stress. Longer sound durations of the target sounds.|
|multisyllabic phrases or words are said while tapping out syllables||“tell me ba-na-na”||This can lead to equal stress on each syllable, making the child sound robotic|
|Decreasing rate||Spending more time on each sound being produced ‘sssuuuuuuuunnnnn’ for ‘sun’||Slow rate of speech|
Historically, speech therapists have not generally been trained to think about what to do with a child with CAS once he or she has obtained all of their sounds and syllable shapes and have increased intelligibility. The focus of treatment is often on improving the motor plans and sequences needed for speech production to increase intelligibility. In other words, the clinician will carefully construct treatment phrases to increase syllable shapes (e.g., bow, boat, boats), sound sequences (e.g., cat and tack), and phrase lengths (e.g., I want more, I want more milk, I want more milk please). During treatment it is easy to fall into accentuating targets unnaturally and thus modeling inappropriate prosody, as in the first example provided in table 2. In addition, motor skill learning principles applied to speech therapy encourage decreasing rate and giving numerous opportunities to practice the motor speech skill. Children will produce utterances in the way they are modeled. That means they will use extra articulatory force, produce multisyllabic utterances syllable by syllable, and prolong syllables, etc. if that is what is modeled. Thus, speech therapists need to be mindful of how therapy is impacting the naturalness of the childs speech as they work on accuracy of sequencing articulatory gestures for clear articulation. Often these unnatural models are necessary for the child to hear, see and feel the appropriate articulatory configurations initially. However, as soon as the child has learned it, the model needs to become more natural.
Treatment efficacy studies that examine what happens to prosody when we increase awareness and effort on correct articulation would be of great benefit. Many treatment techniques do address naturalizing prosody after obtaining accuracy of the speech sounds (e.g., PROMPT, Melodic Intonation Therapy, and Integral Stimulation). It would be worthwhile to examine what the best way is to ensure normal prosody while working on accuracy of sounds. For example, at what point should drilling a more natural sounding motor plan come into place? How long should we focus on correct articulation at the expense of normal prosody? For every child the answer will most likely be different. The important message here is that prosody and articulation are not two separate entities. Thus, speech therapists need be aware of changes in prosody as attention is being placed on articulation. Outside of speech therapy, music and other rhythmic activities, such as dance, could also benefit the childs prosodic development.
We also need to set realistic expectations. A child with CAS may have residual prosodic differences even after they have learned to produce all sounds and sound sequences correctly. For example, some parents have noted that their child is intelligible, but sound as if they have a foreign accent. At some point, we need to dismiss a child from speech therapy even if they dont sound perfect. However, we also need to believe they have reached their full potential. If prosody has not been addressed in speech therapy, we are not done yet.