One of the first principles of clear writing is to get to the grammatical subject early in a sentence, and to get to the verb soon thereafter. Every time a reader encounters a sentence, she wants to know who did what. She may want to know other things too, but she always wants to know that. The reader’s brain is wired, therefore, to look for the subject and the verb (who did what?). When you write sentences that get straight to the subject and verb, you are making life easier for your reader.

Consider this compound sentence from David French:

I discussed public policy and big historic trends, but I tried to focus on how those trends impact individual human beings.

Each of the independent clauses in this sentence starts with the subject and verb: I discussedI tried. Most English sentences start with a subject and verb, by the way; there’s nothing special about this one. I chose this example because all of its nouns are abstract (unless you count human beings, which I don’t). But as abstract as this sentence is, you had no trouble making sense of it, partly because the writer quickly gets you to and through the subject-verb nexus.

When your reader gets through the subject-verb nexus of a sentence, she feels a small sense of relief: Now I know what this sentence is about. Now I get it. Any phrases or clauses that appear before (to the left of) the subject delay that relief and so create tension: What is this sentence going to be about? Anything could happen. This is scary. Possibly exciting.

Tension isn’t necessarily a bad thing; it can keep your reader engaged and interested. But a reader can endure only so much tension before she loses interest or loses the thread of meaning. So writers have to be careful with what are known as ‘left-branching’ sentences—that is, sentences with multiple, lengthy clauses and phrases before (to the left of) the main clause.

In his excellent book The Sense of Style, Steven Pinker quotes the following from a writer who was not careful in the construction of a left-branching sentence:

Because most existing studies have examined only a single stage of the supply chain, for example, productivity at the farm, or efficiency of agricultural markets, in isolation from the rest of the supply chain, policymakers have been unable to assess how problems identified at a single stage of the supply chain compare and interact with problems in the rest of the supply chain.

Can you identify the subject of the main clause of this sentence? It’s policymakers. The much-put-upon reader has to wade through 34 words to get to the very uninspiring clause, “policymakers have been unable.

When you are constructing a sentence, always be aware of where the main clause is. Your reader will be watching for it, even though she probably doesn’t know she is. If you make your reader wait for the main subject and verb, be sure you’ve got a good reason. While it is true that left-branching clauses and phrases allow you to cram more information into a single sentence, that’s not in itself a good reason for left-branching, as you can see in the sentence above, which contains loads of information about the supply chain, agricultural markets, and policymakers, but is almost unreadable.

Let’s experiment with left-branching sentence construction. We’ll start with a main clause, then build to the left and see what works and what doesn’t work. Here’s our main clause:

Roy told Rebecca that he didn’t like her new boyfriend.

Straightforward stuff. Subject-Verb-Indirect Object-Direct Object. The one bit of grammatical fanciness is that the direct object is a noun clause (that he didn’t like her new boyfriend). But that clause is itself straightforward, getting immediately to the subject and verb.

Now let’s build to the left.

After a tedious double date, Roy told Rebecca that he didn’t like her new boyfriend.

This is technically a left-branching sentence, since that adverb clause After a tedious double date comes to the left of the main clause. But a little five-word clause isn’t going to cause anybody any heartache. I spoke earlier in terms of tension and release; this little clause doesn’t create much tension at all before we get to the release of the subject-verb nexus of the main clause.

But look what happens when we keep building to the left:

After a tedious double date in which Rebecca’s new boyfriend talked about himself, name-dropped, accidentally revealed himself to be a fair-weather soccer fan, and generally came across as self-involved and undeserving of Rebecca, Roy told Rebecca that he didn’t like her new boyfriend.

Can you feel the tension growing while you wait for the main clause to arrive? That initial word After signals that you’re just going to have to hang in there for a while until we get “real action” of the sentence, after the after clause (with all its attendant phrases and imbedded clauses) is over.

This left-branching sentence works well enough, I think, because the run-up to the main clause tells a story: the following things happened, and they all led to Roy telling Rebecca what he thought about her new boyfriend.

One way you can get yourself in trouble with a left-branching sentence is to let that left branch get overly abstract, as in the supply chain-agricultural markets-policymakers sentence above.

Consider this revision of the Roy-Rebecca sentence, in which the chain of events depicted in the left branch gets translated into a string of abstract “reasons.”

As a result of Rebecca’s boyfriend’s self-absorption—evidenced by a tendency to name-drop throughout their double date and to be the hero of all his own stories—as well as his fair-weather fandom when it comes to soccer, and his general unworthiness of Rebecca, Roy told Rebecca that he didn’t like her new boyfriend.

Did you feel yourself lose interest before you even got to the main clause? I did, and I’m the person who wrote it!

It’s easy to get yourself in trouble with left-branching sentences. But that is not to say that you should avoid them. Simply be aware that you are trading clarity for tension. And while we all value clarity, clarity isn’t the only thing we value in a sentence. Otherwise, every sentence would sound like something from the Dick and Jane readers.

For Further Reading
I commend to you this article on The Elements of Writing website: “How to Write a Left-Branching Sentence, with Dazzling Examples from Martin Luther King and Maureen Dowd.” The example from Maureen Dowd includes a 156-word run-up to the main clause. The Martin Luther King example is a 316-word sentence in which 305 words come before the main clause! And both sentences are dazzling, as the article’s title promises.