When a person has an articulation disorder, they struggle with the precise motor movements required to form specific sounds, such as coordinating the lips, tongue, and airflow. The concept of an “approximation” is fundamental in speech therapy, serving as a positive, accepted stepping stone toward clear, accurate speech. It represents a temporary, imperfect sound that the speech therapist encourages because it indicates movement in the right direction.
Defining the Approximation
An approximation in speech therapy is a sound production that is acoustically similar to the target sound but is not yet fully correct. It captures some of the desired motor features without achieving the final, perfect articulation. For example, a child aiming for the /r/ sound might produce a /w/ sound instead, which is acoustically close but uses the wrong articulatory placement.
A speech-language pathologist accepts this imperfect sound because it demonstrates that the individual is attempting the correct motor movement, even if the result is distorted. The therapist views the approximation not as an error, but as an attempt that can be built upon. This differs from a simple error or substitution, which may show no shared features with the target sound.
By accepting and reinforcing a close approximation, the therapist isolates a positive movement, such as correct lip rounding or tongue placement, and builds confidence. This early success motivates the individual to continue practicing the motor pattern. The goal is to gradually refine the production until it matches the acoustically correct target sound.
The Role of Successive Approximations
The technique used to move a client from an approximation to a fully correct sound is called successive approximation, also known as “shaping.” This methodology systematically guides the client through a series of small, manageable steps, each getting closer to the target behavior. It relies on identifying a sound or movement the client can already produce that shares some features with the desired sound.
The therapist first establishes the initial approximation and provides positive reinforcement when the client successfully produces it. In the next step, the therapist requires a small, incremental modification, such as slightly higher tongue placement or a tighter lip position. This change must be a closer match to the target sound than the previous step.
Each successive step involves reinforcing the modified sound and then requiring a further small adjustment in the articulators—the tongue, lips, jaw, or palate. This system breaks down the complex motor skill into a chain of achievable actions. This progressive adjustment continues until the client successfully produces the target sound without prompting.
Successive approximation is effective because it prevents the client from becoming overwhelmed by trying to achieve a complex sound all at once. By focusing on tiny changes, the method ensures a high rate of success and uses reinforcement to solidify the new motor patterns. The therapist uses visual cues, tactile stimulation, or verbal instructions to help the client understand the required modifications at each step.
Practical Examples in Articulation Therapy
A common challenge addressed using approximation is the production of the /r/ sound, which is often difficult to master. A frequent approximation is substituting /w/ for /r/, such as saying “wabbit” for “rabbit.” The therapist accepts the /w/ as a starting point because the lips are rounded, a feature shared with the correct /r/ sound.
The next step in shaping the /r/ sound might involve using the /l/ sound, which requires the tongue tip to be in a high position near the alveolar ridge. The therapist instructs the client to slowly drag the tongue backward from the /l/ position while maintaining tension, which helps elicit the bunched or retroflex position needed for /r/. This controlled movement represents the first successive approximation toward the target.
Another frequent example involves the /s/ sound, often approximated with a frontal lisp where the tongue protrudes between the teeth (interdental placement). To fix this, a therapist might use the /t/ sound as a starting point, since both /t/ and /s/ share the alveolar place of articulation near the ridge behind the upper front teeth.
The client is instructed to produce a long /t/ sound (a sustained /t/), and then slowly release the air in a continuous flow without letting the tongue push forward. The therapist modifies the manner of articulation from the brief stop of the /t/ to the continuous friction of the /s/. Each attempt that keeps the tongue behind the teeth and produces a more focused airstream is reinforced as a closer approximation to the correct sound.