Why can we say ‘mice eater’ but not ‘rats eater’? English compounds

One trait that can quickly distinguish mother-tongue speakers from L2 speakers is their use of compound nouns, specifically, the tolerance of plurals in compound nouns. According to Steven Pinker’s book ‘The Language Instinct’, children already know that a cat can be described as a ‘mice eater’ or a house can be ‘mice infested’, but they automatically reject the use of the plural in the compound ‘rats eater’. We can say that a dog bite leaves ‘teeth marks’ on somebody’s skin, but ‘claws marks’ sounds wrong. We can say that a particularly sociable friend is a ‘people person’, but describing a bibliophile as a ‘books person’ just doesn’t sound right. Indeed, we say ‘bookworm’ and not ‘books worm’, even though obviously a plurality of books must be at hand. And why is ‘clothes addict’ tolerated, but not ‘shoes designer’, which would have to be ‘shoe designer’? Let’s take a look at some more compounds in this passage by one of my favourite writers, George Orwell:

“[…] another English characteristic which is so much a part of us that we barely notice it, [..] is the addiction to hobbies and spare-time occupations, the privateness of English life. We are a nation of flower-lovers, but also a nation of stamp-collectors, pigeon-fanciers, amateur carpenters, coupon-snippers, darts-players, crossword-puzzle fans.”

Notice how the first element is always singular, apart from in ‘darts-player’. And while I’m not quite sure what a pigeon-fancier is, I’ll leave you to your own private speculations about that.

Entry 531.1–2 from Swan’s Practical English Usage sheds some light onto the rules governing compound formations. When creating noun+noun compound nouns, or noun+adjective compound adjectives for that matter, English morphology avoids pluralisation of the first noun, regardless of the intended multitude. The only exceptions to this rule are for irregular nouns and pluralia tantum or plurals whose meaning differs from the singular — the latter two, essentially, being cases where the singular is not viable. Pluralia tantum are words that only exist in the plural, such as economics, clothes, scissors, jeans. An example of a word whose plural differs in meaning from the singular is arms (weapons) as opposed to arm (the limb), resulting in the compound ‘arms trade’.

This same rule explains why Orwell writes of ‘darts players’ but not of ‘dart players’; because the plural darts denotes the game as a whole, while the singular dart is a concrete object, a ‘small pointed missile’ as quaintly defined in the OED. The rule for irregular plurals, on the other hand, explains the use of the plural in compounds like ‘people carrier’ (type of large car) instead of ‘person carrier’.

While it is a solid rule that regular nouns are avoided in the plural in the first element of a compound, in my personal experience I find that irregular nouns are less predictable. For example, foot has the irregular plural ‘feet’, but an American would still call their podiatrist a foot doctor and not a feet doctor.

A further example is the irregular plural ‘children’. In this case I believe that ‘child psychologist’ is the correct term compared to ‘children psychologist’; and this even though it could allow the reader the misconstrue the compound as a psychologist who is a child, instead of psychologist who researches children. We say ‘man power’ and not ‘men power’, but ‘people power’ and not ‘person power’. Conversely, the gender-neutral ‘person day’ in human resources lingo (replacing ‘man day’), is a common term and uses the singular, directly in contrast with the plural in ‘people power’. This goes to show how to what extent the construction of English compounds, particularly with regard to irregular plurals, is a veritable minefield.

Despite the inherent difficulties, translators often find themselves needing to adapt long noun phrases into more easily readable English compounds, which makes awareness of the English compound building rules very useful.

A Practical Example

Let’s assume you have to translate ‘informativa sui cookie’ from Italian, i.e. the disclaimer informing a website visitor how their cookies will be used. For the sake of thoroughness, let’s wipe non-compounding translations like ‘notice about cookies’ off the table, which are unidiomatic. There isn’t just one cookie (and the Italian ‘i cookie’ is plural, for the record), so your instinct might be to write ‘cookies policy’ or ‘cookies notice’. A quick corpus search, however, may be able to confute this conjecture.

The Global Web English corpus (GloWbE) has 644 occurrences of ‘cookie policy’ against 149 occurrences of ‘cookies policy’. Likewise 42 occurrences of ‘cookie notice’ and only 4 of ‘cookies notice’. The iWeb corpus shows similar results, with 3,475 occurrences of ‘cookie policy’ and 1,517 of ‘cookies policy’, and 254 of ‘cookie notice’ and 38 of ‘cookies notice’. A simple search in quotes on Google.co.uk returns fourfold results for ‘cookie policy’ compared to ‘cookies policy’. In the spirit of empiricism, I have to report that the News on the Web corpus returns 207,326 instances of ‘cookies policy’ and only 154,253 of ‘cookie policy’, which would contradict my general hypothesis. This could, however, be a result of a skewed dataset, due to deduplication, biased scraping methods and boilerplate removal, common in corpus construction. The figures for ‘cookie notice’ and ‘cookies notice’ in the NOW corpus, on the other hand, are 3,559 and 1,475 respectively, which again confirms the hypothesis.

On the basis of this data, it can be concluded that the singular compound noun construction ‘cookie policy’ is preferred to the plural construction ‘cookies policy’, although this preference is not prescriptive. This finding would also confirm the first rule observed by Swan, which recommends using the singular in compounds if the noun’s plural is regular.

But the plural ‘cookies’ is still found. My only advice at this juncture, therefore, is to use your native sense as to the acceptability of plurals in compounds; some are acceptable, some have a negligible difference, but some sound truly awful. As illustrated above, sometimes the plurally constructed compound is unavoidable; if it isn’t, a translation using the singular or avoiding a compound is almost always a safe bet.

That’s so much for the description of the rule, but in the title I asked why this phenomenon even exists. It is counterintuitive that English speakers avoid plurals in the first element of a compound, even though a plurality is intended. If the irregular plural in people carrier is acceptable, why does the English language then poorly tolerate locutions like ‘babies boom’, a ‘brains drain’ or a ‘trains station’?

Steven Pinker explains that he believes this behaviour stems from the fact that the rule governing the building of compounds acts quicker than the rule governing the construction of plurals, effectively overriding it. Therefore, our brains don’t have processing time to inflect the singular noun into its plural for the first element in compounds. He then suggests that irregular plurals, on the other hand, are hardwired somewhere and do not require computation. Because of this, they do not get drowned out by the higher priority of the compound building rule and have the chance to assert themselves.

Here is the extract from Pinker’s book that discusses it:

Irregular forms, then, live at the bottom of word structure trees, where roots and stems from the mental dictionary are inserted. The developmental psycholinguist Peter Gordon has capitalized on this effect in an ingenious experiment that shows how children’s minds seem to be designed with the logic of word structure built in.

Gordon focused on a seeming oddity first noticed by the linguist Paul Kiparsky: compounds can be formed out of irregular plurals but not out of regular plurals. For example, a house infested with mice can be described as mice-infested, but it sounds awkward to describe a house infested with rats as rats-infested. We say that it is rat-infested, even though by definition one rat does not make an infestation. Similarly, there has been much talk about men-bashing but no talk about gays-bashing (only gay-bashing), and there are teethmarks, but no clawsmarks. Once there was a song about a purple-people-eater, but it would be ungrammatical to sing about a purple-babies-eater. Since the licit irregular plurals and the illicit regular plurals have similar meanings, it must be the grammar of irregularity that makes the difference.

The theory of word structure explains the effect easily. Irregular plurals, because they are quirky, have to be stored in the mental dictionary as roots or stems; they cannot be generated by a rule. Because of this storage, they can be fed into the compounding rule that joins an existing stem to another existing stem to yield a new stem. But regular plurals are not stems stored in the mental dictionary; they are complex words that are assembled on the fly by inflectional rules whenever they are needed. They are put together too late in the root-to-stem-to-word assembly process to be available to the compounding rule, whose inputs can only come out of the dictionary.

Gordon found that three- to five-year-old children obey this restriction fastidiously. Showing the children a puppet, he first asked them, “Here is a monster who likes to eat mud. What do you call him?” He then gave them the answer, a mud-eater, to get them started. Children like to play along, and the more gruesome the meal, the more eagerly they fill in the blank, often to the dismay of their onlooking parents. The crucial parts came next. A “monster who likes to eat mice,” the children said, was a mice-eater. But a “monster who likes to eat rats” was never called a rats-eater, only a rat-eater. (Even the children who made the error mouses in their spontaneous speech never called the puppet a mouses-eater.) The children, in other words, respected the subtle restrictions on combining plurals and compounds inherent in the word structure rules. This suggests that the rules take the same form in the unconscious mind of the child as they do in the unconscious mind of the adult.

[…] Gordon’s mice-eater experiment shows that in morphology children automatically distinguish between roots stored in the mental dictionary and inflected words created by a rule.

Steven Pinker, 1994: The Language Instinct: How the Mind Creates Language (pp. 146–147)

George Orwell, 1942: The Lion and the Unicorn: Socialism and the English Genius