A student wants to use "are described" (because it's passive) in the blank space although the correct answer is "described". How can I explain the grammar of why it is incorrect?
In one study, 43% of employees ____ as being under heavy stress had weak concentration and poor work performance.
In one study, [adjunct]
43% of employees ____ as being under heavy stress [subject]
had [verb at head of main clause]
weak concentration and poor work performance. [object]
The subject here is a noun phrase with employees as the head noun. Noun phrases do not allow verb phrases headed by verbs in present (are) or preterite (were) form as a post-head dependents - that would look too much like a main clause and be difficult to parse as the subject of a larger clause. They do, however, allow past-participial clauses, which is why described is allowed in the blank above.
Some form of relative clause would also be allowed, such as who are described, but would necessitate the inclusion of either who or that as the relativized element is the subject.
In general, phrases can not share a parent unless they are coordinated.1 Therefore, the two uncoordinated finite verbs ("are" and "had") can not head the same predicate. We thus have two predicates2: "are described as being under heavy stress" and "had weak concentration and poor work performance." However, the predicates are uncoordinated; that's a problem because they share the same "parent" (the sentence's "root").
We could fix the problem by coordinating the predicates:
In one study, [43% of employees] {are described as being under heavy stress} and {had weak concentration and poor work performance}.
([] = subject and {} = predicate)
This is grammatically valid but does not seem to represent what the author means. (The disparate verb tenses are also an issue.) The author probably wants the past participle phrase "described as being under heavy stress" to modify the nominal "employees". Past participle phrases can certainly modify nominals, so that works:
In one study, [43% of employees described as being under heavy stress] {had weak concentration and poor work performance}.
As DW256 notes, other solutions are also possible.
(I gave +1 to DW256's answer, which I think is great. The purpose of this answer is to take a slightly different approach to the issue, although both approaches are consistent with each other.)
1 This is a gross oversimplification of a general principle, but it applies to this situation.
2 I'm considering only finite predicates here.
This question already has 3 great answers, but all seem oriented towards more advanced students. OP doesn't specify the grade level of the students in the question, but this approach might be more suitable if they're younger learners. It is a method which helped me when I was elementary/middle school aged:
Here is the sentence from the question:
"In one study, 43% of employees ____ as being under heavy stress had weak concentration and poor work performance."
If the students are confused as to which choice ("are described" vs. "described") should go in the blank, I would assume they aren't clear on either the intended meaning of the sentence, or how the sentence's structure conveys that meaning.
To clear up the confusion, it might be helpful to have the students strip down the sentence to the most basic elements, then build it back up. Maybe ask something like, "Can you write down just the subject, main verb, and direct object of the sentence - think of who did what? Ignore all the modifiers (adjectives, adverbs, prepositional phrases, etc.) for now."
This would give "employees (S) had (V) concentration and performance (D.O.)."
Then, encourage them to add the modifiers back in, one at a time: what kind of concentration and performance ("weak concentration and poor performance")? How many employees ("43% of employees")? etc.
Once they have reconstructed the original sentence and identified which central part (Subject, Main Verb or Direct Object) each modifier adds more information to, ask them to think about which of the two options "are described" or "described" could go in the blank without changing the meaning of the sentence. We've already identified S, V and D.O., so adding another main verb ("are described") in the blank would change the meaning. (Now you'd have "employees (S) are described (V)," and the sentence would fall apart as soon as they try to find where the Dir. Obj. went or how the word "had" fits into the new sentence.)
But, with "described" in the blank, they should now be able to identify it as yet another modifier for the subject of the sentence, "employees". It answers the question, "what kind" of employees - the "described-as-being-under-heavy-stress" kind!
Once the students have gotten past any confusion on how the parts of the sentence fit together (I believe the above exercise should help with that), would be the time to go into more detail about technical terminology like how exactly you'd classify the phrase "described as being...".
The gap in the sentence is a post-modification of the noun "employees". In this case, the post-modification serves to identify or specify which subset of employees is being identified or referred to.
A common way for this particular post-modification to be realised is by a defining relative clause:
In one study, 43% of employees who are described as being under heavy stress had weak concentration and poor work performance.
The relative clause can be shortened by the removal of both the relative pronoun and the passive auxiliary.
In one study, 43% of employees described as being under heavy stress had weak concentration and poor work performance.
This results in what has been called a "reduced relative clause".
For a reduced relative clause to be grammatical, it is necessary to remove both the pronoun and the auxiliary. This is why the student's suggestion:
*In one study, 43% of employees are described as being under heavy stress had weak concentration and poor work performance.
is ungrammatical.
Note: At least one expert contributor to this site has plausible reasons for rejecting the term "reduced relative clause" as a good description of the grammar of this type of post-modification. But the term is in common usage and has an entry in The Oxford Dictionary of English Grammar (p353):
reduced clause: a shortened clause, particularly a non-finite or verbless clause with a post-modifying function that can be interpreted as a relative clause with its relative pronoun and its finite verb omitted, e.g.
- anyone scared of heights is advised not to attempt to climb this tower (= Anyone who is scared of heights...)
*In one study, 43% of employees are described as being under heavy stress had weak concentration and poor work performance.
This sentence is ungrammatical because the relationship between the two finite verbs are and had is unclear, which makes the meaning of the sentence unclear.
For example, the first finite verb can be subordinated by adding who:
In one study, 43% of employees [who are described as being under heavy stress] had weak concentration and poor work performance.
Here, the added who makes it clear that it starts [a subordinate clause] that defines the relationship between the two finite verbs.
The same subordination can be made clear by removing the first finite verb are:
In one study, 43% of employees [described as being under heavy stress] had weak concentration and poor work performance.
In other contexts, the two finite verbs can have a different relationship called 'coordination' by adding 'and':
In one study, 43% of employees are described as being under heavy stress and have weak concentration and poor work performance.
I want to reduce the answer to the simplest explanation. Your student is misunderstanding the sentence structure.
Your student is interpreting a structure like this:
All [walls] are painted yellow.
The core message here is that all walls are painted yellow.
However, that's not the structure being used. The structure being used is:
All [walls painted yellow] are north-facing.
The core message here is that all yellow walls are north-facing. Instead of "yellow walls", they use "walls painted yellow", but the meaning is the same.
The "painted yellow", much like the "described as being under heavy stress" are part of the definition of the walls/employees. It's not the main clause of the sentence.
So, in other words, if the given sentence was this:
In one study, 43% of employees ____ as being under heavy stress
Your student would be correct. The core message is that out of the collection of all employees, 43% of them were under stress.
However, in the given sentence, the core message is that out of the collection of employees who are under stress, 43% of them had weak concentration and poor work performance.
The added words change how you interpret the first half of the sentence, and your student didn't base their interpretation on the sentence as a whole.
If the student struggles with this, give them the following examples, and have them explain what each of them means:
And then move them on to the next example:
If they explain the meaning of the third sentence correctly, you can point out the similarity between the original exercise and the simplified example.
Lots of great answers here, but for a student who cannot identify conjugate verbs and their subjects, I'd keep it even more simple, because they're almost right. I'd just make sure they understand that in "...employees described as..." is a reduced form of "employees that are described as...".
So the student is right that it is a passive form, and they should expect "are", but it happens that because of a grammar rule called whiz-deletion, the relative pronoun and "are" are both elided.
While I grant you your correct answer, I suggest that this sentence is needlessly misleading, and further I would be more likely to penalize the author for writing a misleading sentence rather than the student for misreading it.
I propose adding "the" to imply that the sentence will go on to describe which particular 43% percent of employees are being discussed:
In one study, the 43% of employees ____ as being under heavy stress had weak concentration and poor work performance.
Reading the above, I would be much less likely to misidentify purpose of "___ as being under heavy stress" because now "are described" sounds actively wrong right away instead of only after you reach "had".
The main verb of the sentence is "had". The object is "weak concentration and poor work performance". That leaves the subject as being "43% of employees ____ as being under heavy stress" ("In one study" is an adverbial phrase). Since this phrase is the subject of the sentence, it has to be a noun phrase.
If we put "described" in the blank, then "described as being under heavy stress" is a adjectival phrase that modifies "43% of employees", leaving the entire phrase a noun phrase.
If we put "are described" in the blank, then "43% of employees are described as being under heavy stress" is an independent clause, and independent clauses can't be the subject of a verb, at least not directly.
Clauses can be made part of a noun phrase with a conjunction or preposition; for instance "The fact that 43% of employees are described as being under heavy stress" is noun phrase, with "that" being a subordinating conjunction that makes the clause into a subordinate clause.
In summary, you can pile adjectives and adjectival phrases onto a noun phrase, and it stays a noun phrase. But once you have a finite verb, it stops being a noun phrase and becomes a clause instead. And clauses can't fulfill the roles of a noun phrase. Note that while "was" is a finite verb, "described" is a past participle, which is a nonfinite verb form, so "was" makes it into a clause, while "described" does not.
