As a native English speaker, I would argue that 'We never have had cats' sounds very unnatural, and would be subject to correction if written or said aloud to another native speaker. You can still stress the time phrase 'never', by using the phrase 'We have never had cats'/'We've never had cats'.
Doubles and even triples are common in Italian. The trick to good translation is to resolve to a single negative when translating to English, and learn the patterns when translating to Italian .. here's a helpful list
I've never seen mai used without non before it, so if you translate it as not ever = "never", it's not a double-negative.
I found a number of examples where mai is translated as "ever":
complement: "sempre", "già", "ancora" and "appena" also behave like that. Examples:
- È sempre venuto con me. (= He always came with me)
- L’ho già letto. (= I have already read it)
- Non l'ho ancora trovato ( = I haven't found it yet)
- Ho appena mangiato una mela. (= I only ate an apple)
That's simple past "we never had" = noi non avemmo mai, not present perfect, which uses auxiliary + participle = "have had" Non abbiamo mai avuto.
However, Italian simple past is quite irregular. Other discussions indicate that in northern Italy, it's not used very much, so that present perfect actually does take the place of simple past.
But the lesson is about present perfect, and you used English simple past, so for the moment your answer is wrong.
Unfortunately, Duo has a bad habit of being really finicky, flaky and fickle about translating present perfect (or not). It really depends on the module you're in at the time - but when on general strengthening, you can't tell, so it's just blind luck if you get a present perfect translation correct. I've even been marked wrong when the Italian was clearly present perfect and I've used English present perfect.
The passato prossimo is different from the English present perfect in that it can be (and is very commonly) used for activities that have been completed in the recent past and have no association with or effect in the present. Thus translating it as the simple past is entirely correct. It can also be translated as present perfect where the context suits that translation.
Subject and past participle have to agree when the auxiliary verb is essere; in the current exercise, the auxiliary verb is avere, so there's no subject-participle agreement.
When the auxiliary is avere, the past participle does not change except in one instance: When a direct object PRONOUN precedes the verb, then the past participle has to agree in number and gender with the direct object pronoun. For example:
ho avuto due case = "I have had two houses"
le ho avute = "I have had them [the two houses]"
ho avuto due cani = "I have had two dogs"
li ho avuti = "I have had them [the two dogs]"
l'ho avuto - masculine object "I have had it"
l'ho avuta - feminine object "I have had it".
I have also read that, when the preceding direct object pronoun is not 3rd person, then object-participle agreement is optional. I just stick with agreement, since it's easier, but I'm not certain about this. Examples:
ci ha incontrato = "he has met us" - "us" is 1st person plural, so there is no agreement between object pronoun and participle.
Li ho incontrati = "I have met them" - "them" is 3rd person plural, so there is agreement between object pronoun and participle.
When we've gotten out cats from the humane society, it's always been a quesiton of which cat picks us, not which cat we pick. It makes me think of the scene in Avatar, where Jake goes to get his Banshee, and he asks Neytiri how he'll know when he's found "his" Banshee. Neytiri matter-of-factly says, "He will try to kill you."
Just like cat selection.
There are an uncountable number of words in various languages which have different meanings, depending on the context. It's not inconsistent, it's idiomatic. An example in English is the word "bow", which can mean: the front of a ship, a stringed weapon used to launch arrows, a musical tool used to play stringed instruments, to lean the body forward in a gesture of deference, and to lean the head forward in prayer/supplication or as a sign of defeat.
Just another piece of information for Duolingo: "WE'VE", is a contraction of 'WE HAVE", just like "I'M is a contraction of:" I AM";THEREFORE 'I'VE HAD' imeans the same as saying: I have had, AND IT IS CORRECT ENGLISH AND SHOULD BE ACCEPTED AS SUCH BY DUOLINGO, SO people learning English should receive the coreect information, whether they are paying for it or not. When speaking "I'VE' is used as much, OR EVEN MORE than 'I HAVE'. Another example is 'IT IS'= TO 'IT'S'; 'we've= to 'we have' etc!