Make and Subject Verb Agreement

In class, we were working on subject verb agreement when we came across a sentence like

She makes him work harder.

From the sentence we can see that makes agrees with the pronoun she (3^rd person singular). The question was what about the verb work? We do not have to worry about subject verb agreement with the verb after make.

Make is one of three verbs called causative verbs, that act in this way. These other verbs are have and let.

She makes her try. (causes her to try)
She has her fix her hair. (causes her to fix her hair)
He lets her drive his car. (allows her to drive his car)

The structure is Subject + Verb + Object + Verb + (Adverb or Adjective or Noun Phrase or Clause).

I think that the second verb is actually an infinitive without the to for two reasons. When we restate the sentence in another way as in causes or lets her, we have to use an infinitive form as in to try, to fix, to drive. Another reason it seems to be an infinitive is that the other causative verbs are followed by infinitives.

She gets him to work for her.
She allows him to return late.
She convinces him to stay home.

A list of causative verbs of this second type is: let, help, allow, have, require, allow, motivate, get, make, convince, hire, assist, encourage, permit, employ, force. The list comes from The Guide to Grammar and Writing.

The structure for these verbs differs only in the use of the preposition to.
Subject + Verb + Object + to + Verb + (Adverb or Adjective or Noun Phrase or Clause).