How our language branches right and left

A little understanding of what linguists call parse trees can help writers put sentences together better.

Elizabeth Shafiroff/Reuters
Activists protesting against police brutality hold placards with the names of some 150 people who they said were 'killed or brutalized' by the police, during a demonstration in Grand Central Terminal in New York on Jan. 5, 2015.

Like many of us in the words trade, I keep learning from Steven Pinker’s new book, “The Sense of Style.” 

I’ve even had some insight into “police-involved shootings” – the phrase, that is; note the quotation marks.

Professor Pinker’s mentions of “right” and “left” branching have prompted some research into what linguists mean by these terms. A little understanding of these concepts can be helpful to anyone wanting to put sentences together better.

The branches in question are those of parse trees. These structures resemble the mobiles in a child’s playroom but actually are a way of mapping or graphing sentences, an alternative to Reed-Kellogg diagrams. They would be unusual in the botanical realm in that they grow downward; their roots are at the top. 

When linguists speak of a right-branching structure, they mean one in which the most important element comes first: “Run quickly” is a right-branching verb phrase. A left-branching structure has its most important element at the end: “the big house,” to give an example of a left-branching noun phrase.

English is generally a right-branching language. But it has plenty of left-branching structures – almost all noun phrases, in fact. Consider these, with modifiers piled up before the actual noun: “those 15 giggling girls,” “any unemployed carpenters,” “her homemade pies.”

This concept of branching works at the sentence level, too. A left-branching sentence, in which the introductory material (the setup, a comedian would say) precedes the punch line, can be good for telling a joke.

But a right-branching sentence, with the most important material at the beginning, can work like a train, with a powerful locomotive pulling any number of cars along behind it. 

And left-branching trees are “a hazard of headline writing,” Pinker notes. He cites the Web headline on the obituary of a man who had plotted to knock an Olympic skater out of contention: “Admitted Olympic Skater Nancy Kerrigan Attacker Brian Sean Griffith Dies.” This drew a blog commentary, “Admitted Olympic Skater Nancy Kerrigan Attacker Brian Sean Griffith Web Site Obituary Headline Writer Could Have Been Clearer.”


Now, back to “police-involved shootings,” that unlovely phrase news organizations turned to late last year to refer to a kind of tragedy that suddenly seemed to be happening everywhere. It’s more compact than, say, the right-branching “shootings at the hands of the police.”

More important, the left-branching version puts “shootings” at the end, so it’s available to connect directly with other material: “the police-involved shootings that have shaken our nation,” or whatever. Compare: “the shootings at the hands of the police which have shaken....” Even with which instead of that, we end up with “police” closer to the shaking than is ideal.

The police need to be part of the solution here, but this particular train has got to stop. 

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