Principles of Motor Learning: Variable vs. Constant Practice
Principles of Motor Learning (PML) refers to patterns of learning that have emerged from research into human movement. The bulk of this research has evolved from disciplines outside of Speech-Language Pathology (e.g. exercise and sport), and the research within our field though growing, is still in its very early stages. Nevertheless, PML are increasingly being investigated as they apply to speech therapy in the hopes that a solid understanding of PML can help Speech-Language Pathologists optimize their work with patients/clients struggling with motor speech challenges, such as Childhood Apraxia of Speech. Dr. Edwin Maas has been at the forefront of synthesizing the applications of PML research to Speech-Language Pathology. He has an excellent video on the Apraxia Kids On-Demand Webinars library, and his team's tutorial on Principles of Motor Learning in the Treatment of Motor Speech Disorders is published in Volume 17 of the American Journal of Speech-Language Pathology. This blog post series will summarize some of the key PMLs has outlined in those sources.
Principles of Motor Learning as they pertain to speech therapy apply to two broad categories of intervention: Practice Conditions and Feedback Conditions. Practice Conditions in a nutshell are what the patient/client/student does, Feedback Conditions are what the therapist/communication partner does. Practice conditions refer to aspects such as how much the individual practices, and how often, while feedback conditions refer to how and when the therapist/communication partner responds to what is being practiced.
This post is part of a PML series, and will highlight the Practice Conditions: Variable vs. Constant Practice. For additional PML and more in-depth discussion, please refer to the sources listed above.
Variable vs. Constant Practice
Is it better to do the same this over and over or to mix it up? Intuitively, it might seem that constant practice - doing the same task over and over - beats variable practice. Nevertheless, the research we have points to a more nuanced conclusion. In general motor research, there is research to support the idea that constant practice followed by variable practice is optimal for learning and transfer. Applied to motor speech, this would suggest that when establishing a new motor pattern, constant practice may be preferable, but when working on transfer, variable practice is likely a better bet.
There is limited research directly in the speech population. Generally variable practice was not found to have significantly differed from constant. One study did find a large amount of constant practice less effective for retention than a large amount of variable practice in the childhood apraxia of speech (CAS) population. So yes - repeat a LOT, but make sure to mix things up during the repetition. For example, if you have a child struggling with bilabial closure for /p/. this might mean considering whether your targets remain bilabial to low vowel, or mixed bilabial to/from high vowel. Other ways to incorporate variable practice might be to change prosody or volume, and or to vary tasks.
Constant vs. Variable Practice in Action
The poems in Party Animals! are intentionally highly repetitive - the animal name is repeated inherently facilitates constant practice for children who would benefit from practicing a single word (syllable shape) at a time. (There is an inherent overlap with massed practice here, so the same example from my previous PML blog post applies.) For example, in the poem Beach Baboon, the word "Baboon" (potential targets: CVCVC, lip rounding in a CVCVC, lip closure for /b/ in a CVCVC). The predictable poem structure makes it easy to read the poem as a cloze-sentence task, where the child can finish the adult's sentence. All poems in Party Animals! follow this structure.
Beach Baboon is comprised of exclusively words beginning with /b/, so that children who need to master /b/ and can manage /b/ in a variety of syllable shapes can get constant practice of that target.
Constant vs. Massed Practice
At this point, it might be helpful to distinguish between Massed practice vs. Constant practice.
It might be confusing because both are Principles of Motor Learning that fall under the umbrella of Practice Conditions, and would appear to be referring to a similar idea of multiple repetitions of a singular target.
However, Massed Practice is a distribution condition (in which intervals practice is scheduled):
Constant practice is a variability condition (how consistent are the items being practiced).
Though constant practice and variable practice are opposites, they can both be attributes of either/both massed practice and distributed practice.
Variable vs. Constant Practice in Action:
The variability conditions could include:
speech contexts: the degree of consistency in surrounding vowels, or syllable shapes of target words.
e.g. lip closure for /b/ to a high vowel as in "bee" vs. lip closure for /b/ to a low vowel as in "baa"
prosodic contexts: the degree of consistency in intonation, volume or rate.
e.g. lip closure for /b/ in CV word in quiet voice vs. a loud voice. (bee vs. BEE!!)
elicitation contexts: the degree of consistency in elicitation tasks - e.g. consistent repetition tasks, or varying repetition with picture naming
e.g. lip closure for /b/ in a CVCVC word in: repetition vs. retell task.
To learn more about Principles of Motor Learning, check out our other blog posts on the topic:
Principles of Motor Learning and Childhood Apraxia of Speech: a (hopefully) Gentle Introduction Presented by Dr. Edwin Maas
Principles of Motor Learning in Treatment of Motor Speech Disorders, Maas Edwin, Robin Donald A., Austermann Hula Shannon N., Freedman Skott E., Wulf Gabriele, Ballard Kirrie J., Schmidt Richard A. (2008) American Journal of Speech-Language Pathology