When to use direct object pronoun vs. direct contracted object pronoun (te vs. ti)?

Question

I am wondering when to use (me/te/lui/lei/noi/voi/loro) instead of (mi/ti/lo/la/ci/vi/li) following transitive verbs that take direct objects.

Example 1: I love him

• Direct object: him = lui or lo
• Translations: "amo lui" or "lo amo"

Example 2: Do you love me?

• Direct object: me = me or mi

• Translations: "ami me?" or "mi ami?"

What is the purpose of having (me/te/lui/lei/noi/voi/loro) if they seem to always be replaced in front of the verb with (mi/ti/lo/la/ci/vi/li)?

For your information, I am using the 'contracted' terminology from this video: https://www.youtube.com/watch?v=ho59zl7EvqE&index=51&list=PLqV3q3GTbu4oMXTBReVb0UVk1TYFkBgFz

Grazie, ciao!

Answer 1

What you have called "direct object pronouns" and "direct contracted object pronouns" correspond respectively to which Italian grammar texts call "forme toniche" and "forme atone" of personal pronouns. As you have stated in your question, the "forme atone" are more common, but, according to Federica Colombo in the book Grammatica e pratica della lingua italiana per studenti stranieri, there are some situations in which the "forme toniche" are used (I report the exact text from the book and then I'll try to explain in English).

Le forme toniche dei pronomi personali vengono usate nei seguenti casi:

• quando seguono una preposizione semplice o un'espressione con valore di preposizione:
  Lo faccio per te! / Sono partiti senza (di) lui.
  Ciò accade anche dopo la preposizione a, quando esprimono il complemento di termine e si vuole dare particolare rilievo alla persona.
  Regalo questo libro a te, perché so che ami l'arte romanica.

• senza preposizione, quando esprimono il complemento oggetto e si vuole dare particolare rilievo alla persona:
  Cercavi me? (Cercavi proprio me e non Luigi?)

• in alcune espressioni fisse dopo avverbi (come, secondo, ecc.) e aggettivi (povero, beato, ecc.):
  Secondo me ha ragione Simona. / Beata te che vai in vacanza!

That is, the "forme toniche" of personal pronouns are used in these three cases:

• after a preposition or an expression with a prepositional function:
  Lo faccio per te! / Sono partiti senza (di) lui.
  This happens also when the pronoun acts as indirect object complement and goes after preposition a if you want to put a special emphasis on the person the pronoun refers to:
  Regalo questo libro a te, perché so che ami l'arte romanica.

• when the pronoun acts as direct object complement if you want to put a special emphasis on the person the pronoun refers to:
  Cercavi me? (Cercavi proprio me e non Luigi?)

• in some fixed expressions after adverbs (come, secondo, ecc.) or adjectives (povero, beato, ecc.):
  Secondo me ha ragione Simona. / Beata te che vai in vacanza!

In fact, in your question you are asking about direct object pronouns: this corresponds to the second point of the explained above.

Answer 2

Both forms can be used interchangeably, and it is a matter of emphasis and context whether you want to use "amo lui" instead of "Lo amo".

If you wanted to specify what or whom the object of the action is (example 1), you would use the construction "amo lui"; also, you would use this form where the object plays a role in a subordinate sentence (example 2).

In all other cases you would say "Lo amo"(examples 3-4). In particular, if the object of the action (amare, in your example) appears already in another proposition (example 3), you will most definitely use "lo" to refer to it.

Example 1:

-Chi ami?

-Amo lui!

Example 2:

Non riesce a capire che io amo lui, e nessun altro!

Example 3:

Giacomo non riesce a capire che lo amo.

Example 4:

Mi piacerebbe potergli dire che lo amo.