Can we use an adjective to modify a verb?

Question

'A confident person speaks a little stronger, stands a little taller, and looks a little bolder'.

I read the sentence in the book Instant Voice Training.

In this sentencen, both the verb speaks and stands are modified by an adjective, stronger and taller. What I have found on google is that an adjective can only follow a linking verb as complement of the subject. But in this case, the only linking verb is look, both speak and stand are action verb. So what is the grammatical facts of it?

I assume that there are ellipses. It probably should be speaks in a way that is a little stronger , stands in a way that is a little taller. Is that right?

Answer 1

'A confident person speaks a little stronger, stands a little taller, and looks a little bolder'.

There is no ellipsis. As you've noted, "look" can be followed by an adjective. The same is true of "stand":

stand verb (STATE) C1 [ I, L only + adj ] to be in, cause to be in, or get into a particular state or situation:

How do you think your chances stand (= are) of being offered the job? The national debt stands at 55 billion dollars.

The house stood empty for years.

Martina is currently standing second in the world listings. ( http://dictionary.cambridge.org/dictionary/english/stand?fallbackFrom=british-grammar )

So, you can indeed "stand tall" (and hence "stand taller" or "stand a little taller").

"Speak strong" is less normal, but I don't think there is any ellipsis. "Speak stronger" is just being used as an informal substitute for "speak more strongly".