Prof. John McWorther, in his course on Linguistics, said, in a lecture about principles and parameters: "if a language is pro-drop, the verb attraction parameter is always set on. If a language isn't pro-drop, then it could go either way." Using his examples:
John often kisses Mary (English, pro-drop: off, verb-attraction: off)
Jean embrasse souvent Marie (French, pro-drop: off, verb-attraction: on)
Beso normalmente Maria (Spanish, pro-drop: on, verb-attraction: on)
The examples above show that in English, the verb comes after the adverb, while in French, the verb comes before the adverb (it has moved from its original V
position to the T
position up in the tree). In Spanish, which is a pro-drop language, the verb has to come before the adverb, as in French. Now, consider the same example in Portuguese:
Normalmente beijo a Maria (Portuguese, pro-drop: on, verb-attraction: off)
This piece of evidence seems to contradict the hypothesis above. In Portuguese, the subject pronoun can be omitted (pro-drop), but the verb does not have to move (although you could also say "beijo normalmente a Maria"). How can this be explained?