Let’s look at one sentence very closely to see how it works and doesn’t work. Imagine a psychologist writing about a young patient. The writer is making interesting, indeed moving, observations, but this first draft is overwritten, obstructing the free flow of her sympathetic attention: The argument crystalized and froze the boy’s psychological development which led to a breakdown in his education and homelife and interfered with his healthy psychological growth. How can we change the structure of this draft sentence to sharpen its force?
We can see the sentence in halves, the first as an independent clause with two verbs (The argument crystalized and froze the boy’s psychological development), and the second as a subordinate clause with two verbs (which led to a breakdown in his education and homelife and interfered with his healthy psychological growth). We generally define a clause as a group of words with a subject and a verb, so to say that each of these clauses has two verbs might sound incorrect. But a more accurate definition of a clause is a group of words with a subject and a predicate. The predicate is that part of a statement which is saying something about the subject, and we might very well wish to assert more than one action about the same subject. That is what is going on here. In the first half of the sentence, the subject argument undertook two actions, crystalized and froze, and in the second half, this crystalizing and freezing led and interfered with the boy’s growth. When a predicate has, like this, more than one verb for the same subject, it is called a compound predicate, and for purposes of analysis we may regard the two verbs as making up one more elaborate predication about the same subject.
But elaboration can overwork itself into embroidery, and so it is good practice when we find ourselves writing a compound predicate to ask whether we are making a distinction without a difference. To crystalize something and to freeze it are both kinds of solidifying, and it is likely that the writer was thinking about the hardening effect the argument had had on the boy, and wanted to thread the picture tightly for the reader by choosing a more descriptive verb. That she did well by writing crystalized, but she then threaded the same part of the fabric again by adding the second verb froze. That kind of verbal overstitching is called doubling, and we are most prone to double our assertions in a first draft, where we are more often composing with our conversational voice. Less, however, is usually more in the written statement.
We cannot take this adage of less is more too literally, though, especially in matters of punctuation. The second half of our sentence begins with the relative pronoun which, and the writer has chosen not to include a comma before it. That choice brings us to the delicate topic of what is called the general reference of pronouns. A pronoun must have an antecedent, the noun to which the pronoun refers, and when the true antecedent of the pronoun is not the immediately preceding noun, we must insert a comma between the two to tell the reader just that. What it is that ultimately led to a breakdown in the boy’s education was not his psychological development, the noun immediately preceding the relative pronoun, but the fact that the argument crystalized that development. We should place a comma, then, before the pronoun which to break it from its likely antecedent, development, and associate it correctly with its logical one, the general idea implied by the action of crystalizing.
If we then reorder the events in the subordinate clause so that they move more naturally from home to school, and then transform the verb interfered into a participle, we have this as one possible revision: The argument froze the boy’s psychological development, which led in turn to more troubles at home and difficulties at school, all interfering with his healthy psychological growth. One word longer than the original, in fact, but structurally neater and for that, lighter and quicker.