If you detect this sort of problem, a language evaluation is needed so that you can gain better insight into the nature of their task failure. Phonation is the ability to make any sounds. Up to this point, everything we've discussed is fairly global or diffuse. But, with language, we see that hemispheric dominance is important. Most people are left hemisphere dominant for handedness and language functions, so the language tests rely primarily on the left side of the brain.
Language assessment includes tests of fluency, naming, comprehension, and repetition, at a minimum.
Sparse, effortful speech, often with obvious frustration, is a clue to dysfluency. The former requires the patient to provide the name of objects that you point to. During these tests, listen for paraphasic errors such as literal, verbal, or neologistic paraphasias. It's usually obvious when errors occur. Subtle comprehension deficits can be unmasked by such techniques.