Hi zpr, There isn't a blanket rule for all causative verbs: it depends on which verb it is and whether it's being used transitively or intransitively. You might find this page useful: http://grammar.about.com/od/c/g/causativeverbterm.htm. Here's one of their examples... In the two sentences below, notice that the causative verb "allows" is followed by an object (students) and an infinitive (to e-mail . . . to share), while the causative verb "lets" is followed by an object (students) and the base form of the verb (select). - "Ms. Gonzales also allows her students to e-mail her with important, class-related, or funny information they find in everyday life—this allows her students to share their lives with her in many ways." (Cathy Collins Block and John N. Mangieri, Exemplary Literacy Teachers, 2nd ed. Guilford Press, 2009) I hope that helps. Jon

Okay, I'm no English-expert here, but my guess is that it's because "to make (someone do something)" isn't considered causative in a literal way, like "to cause" actually is. Does that make sense? My point here is if you use "to cause" instead, the sentence will be "she causes me to laugh" while "to make" changes the sentence to "she makes me laugh". Now obviously the latter is much more natural and I have yet to hear someone say "they caused me to OOO", lol.

Not just a habit :) it's the correct way

In English modal verbs (such as will, would, can, could, shall and should) take what we call the zero infinitive. This is the form of the infinitive without the word 'to,' in front of it - for example 'win,' rather than 'to win.' "I would win if we played the game again." This rule also applies to two non-modal verbs. Those verbs are "to make," and "to let." The sentence above uses the verb "to make," so it has to use the zero infinitive. This is why there is no 'to,' in front of laugh.