My 4-year-old son Adam has an autism spectrum disorder, and is undergoing some early intervention therapy to learn explicitly what most kids learn by osmosis. Many of his learning programs are intended to give him social skills, and one of these skills is to be able to say the formulaic responses for common situations. One of these targets is for him to say, "I'm doing fine," when asked, "How are you?" Realizing that this question is not a request for information is one of the things that autistic-spectrum kids often have trouble with.
Adam has done well with this target. Of course, "I'm doing fine" is just a start, enough to get him through the most common social-greeting situations. But to truly master this social skill, he'll need to generalize it, so that eventually he can recognize and use other possible responses, be able to ask someone else how they're doing, and know when he can get away with replying, "Not so good, actually." And maybe one day his generalization will be so advanced that he will confidently answer, "Not much!" when asked, "How ya doin'?" and "Pretty good!" when asked, "What's up?"
Today, though, Adam did some generalizing with the pronoun and the tense in the target response. He was finishing his lunch when his therapist returned from her own lunch break. She asked, "How was your lunch?"
Adam said, "It was doing fine."