When a speech pathologist (SLP) evaluates a child's articulation, not only does he or she listen to and evaluate every speech sound, but the SLP will analyze the errors for patterns of mispronunciation. This will often help him or her devise the best and most efficient therapy plan.
Some speech sounds are very similar. Two different sounds may be produced with the exact same tongue movement. They may be explosive, short sounds, like t, k, and p. Or they may be stretched out “sibilant” sounds like s or f.
Sounds that differ from each other by only one feature are referred to by speech pathologists as “minimal pairs.” The most common minimal pairs used in speech therapy are the voiced / unvoiced sound pairs. Speech sounds can be produced with the voice on (all vowels, / r /, / l /, / z /, etc.) or with the voice off (/ s /, / t /, / k /, etc.). There are many English sounds that are actually almost identical to another sound in their production. The only difference is whether the voice is “turned on” or “turned off.”
Say, “sssssss.” You did not use your voice, did you? Now say, “ssssss” and turn on your voice. The / s / just turned into a / z /! The placement of the tongue and the manner of articulation is identical for the two sounds. Only the voicing is different. This is something that never occurred to me until I was taking courses in speech pathology, so I thought it might be new information for my reader, too!
These are the minimal pairs that differ only in voicing.
th (thin), th (that)
When a child is in speech therapy, the voiced / unvoiced pairs will usually be taught at the same time. It is very common, for example, for a child to work on the / s / and / z / sounds together. Practicing one of these sounds will reinforce the other. At other times, the speech pathologist will choose to focus on sounds that have a different common feature, such as voiced sounds or tongue-tip sounds. Alternately, the SLP may choose several sounds that have no common features-this procedure has been shown to encourage the acquisition of many sounds that are not even addressed!