Some sounds are much harder than others for young children to make. This is especially true of the consonants (everything but “a,” “e,” “i” “o” and “u”). If the sound involves a clearly visible movement of the lips, the young child can imitate the movement and come up with a good approximation of the correct sound. So it’s more than chance that babies often come up with “ma-ma” as one of their first “words,” even though they may not mean their mothers when they produce the sound. They can see you put your lips together and notice that the sound comes out when you separate them. You have the same thing with “b” and “p.”
The sounds “k,” “g” and “r” are far more difficult. The movements needed to make them are essentially hidden. “K” and “g” are made the same way, only “k” is called a “breathed” consonant and “g” is called “voiced.” Try making those sounds yourself, and you will immediately realize that you make the same movements inside your mouth but that you add the voice when you want to make the “g.”
We know that even young babies can make these sounds, as they produce them when they randomly babble. But making them when you want to produce a specific word is a different matter. And “r” is a real challenge. It is not by accident that, when we want to caricature baby talk, we almost always substitute “w” for “r,” as in “I saw a ‘wabbit.’”
As far as helping your child change these patterns, I wouldn’t work at it too diligently. Make sure you use those difficult sounds correctly and don’t fall into the habit of thinking her substitutions are cute and repeating them when you talk to her. Time, and hearing the sounds pronounced correctly, will probably take care of the problem. The substitutions your daughter is making are very common, and the child usually makes the necessary changes on her own. If by age 5 or 6 they are still prominent, I would try to get an evaluation in a speech and language clinic and follow the specialist’s recommendations.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.