In most languages, there are situations in which two different sets of rules can apply. Sometimes it's because there are simply two valid ways of saying something. For instance, in English we can say:
There is none.
There isn't any.
They both mean the same thing and they are both correct. How to choose?
In Italian, a case in point is when we have a modal verb, a verb in the infinitive, and a pronoun. I can attach the pronoun to the verb or I can separate it and change the word order. It's a matter of personal choice.
Vado a cercarlo.
Lo vado a cercare.
Non posso farlo.
No lo posso fare.
Some rules change over time because the rule gets broken so many times that it becomes acceptable to break it. One example of this in English is using "who" instead of "whom" when it's an object. In some cases we still use it, and it is absolutely correct, but in general conversation, people might look at you strangely or think you are a snob. We still use it when we have a preposition before it, as in business letters, for instance: "To whom it may concern."
In a recent episode of Provaci ancora prof!, there's another use that has become less common in everyday speech, but is nevertheless correct. This brand of agreement is what we call facoltativo (optional). The conversation between Renzo and Camilla seems like the perfect opportunity to shine a light on it.
Lo sai? -Lo so, ti ho vista.
You know? -I know. I saw you.
-Mi hai vista? -Sì, ti ho vista.
-You saw me? -Yes, I saw you.
Ero venuto lì per cercarti e ti ho vista.
I went there to look for you, and I saw you.
Captions 5-7, Provaci ancora prof! - S1E4 - La mia compagna di bancoPlay Caption
We're talking about the transitive verb vedere, which takes the auxiliary verb avere. The sentences are in the passato prossimo, thus we use the past participle of vedere. If we look at a conjugation chart, we will see that visto is the past participle, not vista! Vista is nowhere to be seen.
If you click on "play caption," you will hear that Renzo (the husband) is talking to his wife Camilla and then she answers. So what's the story with vista?
There's a rule that if the verb is in the passato prossimo, the past participle can agree in gender and number with the direct object pronoun. Read more about this (in Italian).
So Renzo says Ti ho vista. Camilla is the direct object of vedere. If the roles were reversed, Camilla would say: T'ho visto because the pronoun would correspond to a male, her husband. This doesn't apply only to people. The pronoun might refer to a thing, but all nouns have gender in Italian.
A few more examples:
Ho visto le ragazze – Le ho viste = I have seen the girls – I have seen them
Ho sentito gli spari – Li ho sentiti = I have heard the shots – I have heard them
We should mention that Camilla is a professoressa of Italian and often plays sophisticated word games with her husband, so it makes sense for them to use correct Italian, and in fact, they sometimes get competitive about it. But normal people in everyday life often do not always make this choice and it's optional, so don't worry about it too much, but you might hear it. Still, it's nice to recognize it, right? And when you use it, you will feel proud and in the know.
In the same conversation, Renzo talks about seeing Camilla with Gaetano, the chief of police.
Non negare, vi ho visti.
Don't deny it, I saw you.Play Caption
He could have said Vi ho visto, just as he could have said T'ho visto in the previous example.
As you watch Yabla videos, you will undoubtedly come across more examples of this construction. Feel free to point them out in the comments section.
Devo dire la verità, che io adoro la panzanella
I have to tell you the truth. I love panzanella
e sono una toscana DOC [di origine controllata],
and I'm a DOC [true] Tuscan,
ma non l'ho mai fatta!
but I have never made it.
Captions 12-14, In cucina con Arianna - la panzanellaPlay Caption
And another example, with another verb, from the same cooking video with Arianna:
L'ho sempre mangiata molto volentieri,
I have always really enjoyed eating it [I have always eaten it willingly]...
Caption 15, In cucina con Arianna - la panzanellaPlay Caption