Past participle and changing endings with auxiliary verb "avere"

Question

I have read many times that the endings of the past participle doesn't change when used in conjunction with the auxiliary verb "avere". However I am increasingly noticing that is is not the case. For example I recently came across:

Li ho messi in tasca

Maybe this particular example is wrong or colloquial, I don't know, but I've seen it enough times to make me think this is acceptable. However, I can't find any reference to this in any of my textbooks, nor online. Can anyone help?

Answer 1

With a pronoun as object, the only allowed form is the one you used: nobody would say "*Li ho messo in tasca". With an explicit object, the participle is invariable: "Ho messo i libri in tasca". When the pronoun is a direct object and precedes the verb, as in the example given, then the past participle agrees with the direct object.

Answer 2

Past participles definitely do change according to the object gender and number for transitive verbs when the object is a pronoun, like in your example. They do not, however, change if the verb is intransitive, even if its passato prossimo uses “avere”, like “ho pranzato”.

(some examples, as requested in comments)

Transitive verbs - singular subject

• Ho visto una casa — singular explicit object (una casa). Base participle form.
• Ho visto due case — plural explicit object (due case). Base participle form.
• L'ho vista — singular pronoun as object (la). Participle gains the pronoun gender.
• Le ho viste — plural pronoun as object (le). Participle gains the pronoun gender & number.

Transitive verbs - plural subject

• Abbiamo visto una casa
• Abbiamo visto due case
• L'abbiamo vista
• Le abbiamo viste

No effect on participle.

Intransitive verbs

• Ho pranzato
• Abbiamo pranzato
• Claudia ha pranzato

Again, no effect on participle.

Tricky cases

• Le ho detto — Le is not the object, but complemento di termine.

Answer 3

The past participle used with avere and the passato prossimo as tense doesn't change basing on the grammar gender and the plurality of the direct object. You say ho messo a posto il frullatore and ho messo a posto i temperini nel cassetto.

Since there is li, the past participle is declined basing on the plurality of the direct object. For example, it's Li ho messi in tasca. In the case the sentence is referring to cartoline, for example, the sentence becomes Le ho messe a posto.

Answer 4

The question of past participle agreement with auxiliary verb "avere" when direct object is present in the sentence is covered in sections 365 to 369 of the book Italiano by Luca Serianni. In section 365 this author explains:

Si ha [...] obbligo di accordo quando il participio si riferisca a uno dei seguenti pronomi atoni precedenti: lo, la, li, le.

That is, agreement is compulsory when participle refers to one of these pronouns preceding it: "lo", "la", "li", "le".

This book gives these examples:

• "io vedo sempre lui che me l'ha data, questa libertà" (Pirandello, Il giuco delle parti, III 33).
• "Di quei funghi si fece, in famiglia, un gran parlare: e i miei fratelli dissero alla mia nonna paterna [...] che li avremmo cucinati e mangiati" (Ginzburg, Lessico famigliare, 31).

As explained by Treccani Encyclopedia, another case in which agreement of participle with direct object is compulsory is when the pronominal particle "ne" is used as a partitive with the function of direct object, as in these examples:

• di film, ne ho visti parecchi
• ho comprato delle mele e ne ho mangiate tre (Cordin 2001: 650).

There are other instances with auxiliary verb "avere" in which agreement of past participle with direct object is optional, with a tendency in modern Italian to not do such agreement. They are covered in detail in Serianni's book. Some of them are explained in this article by Accademia della Crusca.