Ni el aire ni el agua ESTÁN contaminados? (Plural verb instead of singular?)

In English, this neither/nor  construction would require a singular verb, rather than plural. TV news broadcasters often get it right, but many people (perhaps even most, these days) do use the plural incorrectly. Strictly speaking, does Spanish also call for a singular verb here? Or is the plural actually the grammatically correct form?

Note: Curiously, the English translation of this sentence in the lesson did use the singular, despite the plural in the Spanish.

Some additional research into the topic indicates that, in Spanish, the plural verb is indeed usual in this kind of construction.

I am able to see some "logic" in that by looking at Spanish constructions that use "either/or" (i.e., o ... o). With "o ... o" (according to my reference), singular vs. plural is optional. The use of the singular emphasizes the exclusivity of the two choices -- i.e., one or the other, but not both. The plural, on the other hand, allows for both to be true.

Applying that kind of thinking to the "ni ... ni" situation can seem to suggest using the plural verb (if you don't overthink it), because we are now excluding items, instead of including, and both items are always being excluded. This is not to suggest that that is why the plural is used. The answer to "why" in language is usually just, "because that's the way it is." This is only a way to help form a rationale for using (and remembering to use) the plural, given the strict singular requirement in English.

¡Hola Tomás71!

You are on the right track with your findings: it is possible to use either a singular verb or a plural one with o ... o and ni ... ni constructions. Both are acceptable.

It is also true that with o ... o constructions, using a singular verb rather than a plural one can imply that you are being much more exclusive, and are referring to definitely just one of the options and not both. With ni ... ni constructions, a plural verb seems to be more common. However, it is also true that Spanish speakers will often use a plural verb when the subject comes first, and a singular verb when the subject comes second. Thus, for the sentence "Neither my brother nor my sister is here," we could have either of the following:

Ni mi hermano ni mi hermana están aquí. 
or
No está aquí ni mi hermano ni mi hermana.

For grammar points like this, I generally go with your final point and say that they're a bit like math: if you avoid asking for the exact "why" of the matter and simply learn the rules, you may have an easier time. :) Sometimes that rationale can be a bit hard to find!

I hope that this helps!

Saludos,

Liss

Thanks, Liss. That does help.

As for not asking why, to make it easier, I certainly tend to agree, where language is concerned (although having a rationale can sometimes make the rules easier to remember). On the other hand, language "rules" tend to be based on usage, of course, and usage evolves in unpredictable ways (and most languages don't have an RAE to slow down that evolution). 

In English, for example, (what I see as) the horrible habit that people have acquired of saying "between he and I" (or "she and I") instead of the correct "between him and me" may very well be considered acceptable at some point. But I still cringe every time I hear it. On the other hand, Spanish does use the nominative "entre él y yo". No doubt the growing hispanic population in the U.S. will influence (and may already have influenced) English grammar usage.

Whether this particular grammar issue is an example of such influence is certainly outside my areas of expertise. But my own inclination is to believe that this practice emerged as a response to students being continually reminded to say, "He and I" (or "She and I") instead of "Him and me" as the subjects of a sentence. And then people misapplied it to objects of prepositions, as well, because they lacked an understanding of the difference.