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How to avoid dangling modifiers

Modifiers are words or phrases that give information about other words or phrases in the same sentence. They make your writing more interesting to read and help you to convey your meaning clearly and accurately. But only if you use them properly.


If it is not clear which word or phrase the modifier is supposed to be modifying in a sentence, the modifier is said to be ‘dangling’. Dangling modifiers can make the meaning of a sentence ambiguous or worse still change the meaning completely. In this blog article, I describe how to avoid dangling modifiers in your research paper so that your sentences say what you want them to.

Dangling participles

Participles are forms of verbs that usually end in –ing (in the case of present participles, e.g., treating) or –ed (in the case of past participles, e.g., treated). They can be used in different ways:

  • They can work with auxiliary verbs to form a multiword verb:

The patients were treated with statins to reduce their cholesterol levels (were = auxiliary verb; treated = past participle; were treated = multiword verb).

  • They can be used as adjectives in a sentence:

Reduced cholesterol levels were observed in the statins group

or as adjectives in compound modifiers:

Statins are cholesterol-reducing drugs.

Dangling participles occur when the word that the participle is supposed to be modifying is not present in the text:

Running at a faster pace, the heart rate increased (Incorrect)


The heart rate was running at a faster pace? Obviously not. We need to clarify who is doing the running for the sentence to make sense. Let’s try again:

When the participant was running faster, their heart rate increased (Correct).

That’s better. Now we understand that the study participant's heart rate has increased because they were running faster. You could make the sentence more concise by using the past participle (ran) instead of the present participle (running):

When the participant ran faster, their heart race increased.

Remember to keep the subject and verb close together. The following sentence:

Running at a faster pace, the heart rate increased in the study participant

is still ambiguous. Your reader will have to stop reading while they figure out who or what is supposed to be running. And you should never interrupt your reader.

Dangling gerunds

A gerund is a participle that takes the place of a noun in a sentence (e.g., family planning). A dangling gerund implies that somebody or something is doing the action, but does not specify who or what this is. Take a look at the following example:

Intensive follow-up strategies improve the outcome of curative surgery after stopping chemotherapy (Incorrect).

The dangling gerund (stopping) has altered the intended meaning of this sentence. Reading this, we assume that intensive follow-up stopped chemotherapy as well as improving the outcome of curative surgery, which is not true. A better phrasing would be:

Intensive follow-up strategies improve the outcome of curative surgery after chemotherapy is finished (Correct).

Prepositional phrases

A preposition is a word that indicates where something is or when something happened (e.g., in, on, under, over, after, before, at). Prepositional phrases include a preposition and its object, and can be used as adjectives or adverbs in a sentence. For example:


After several months of rehabilitation, the patient could walk again (Correct).


Here, the prepositional phrase (after several months of rehabilitation) is functioning as an adverb because it tells us when the subject (the patient) was able to walk again. For this construction to be clear, the prepositional phrase must be close to its subject. If the two become separated, the meaning of the sentence will change:


After several months of rehabilitation, the doctors confirmed that the patient could walk again (Incorrect).


Did the doctors endure several months of rehabilitation before they were able to confirm that the patient could walk again? Not a likely scenario – most doctors are able to make a simple observation without rehabilitation. Although your reader will likely use their logic to interpret what it is you want to say, you should rephrase this sentence:


The doctors confirmed that, after several months of rehabilitation, the patient could walk again


is clearer.

Dangling infinitives

An infinitive is the basic form of a verb with the word to in front of it (e.g., to run, to jump, to sing). Infinitive phrases can play different roles in a sentence. Take a look at this example:


To develop into a mature organism, implantation into the uterine lining is essential (Incorrect).


Here, the infinitive phrase (to develop into a mature organism) is functioning as an adverb because it explains why the action (implantation) is necessary. However, we do not know what is implanting. An expert in reproductive biology will probably infer that the subject is a fertilized egg. But not everybody who reads your paper is an expert in your field. To make sure the meaning of the sentence is clear, we need to introduce a subject:


To develop into a mature organism, the fertilized egg must implant into the uterine lining (Correct).

If only. . .

Be careful with adverbs and adjectives like almost and only. It is important to put them next to the word or phrase they are modifying , or you may find yourself saying something you do not mean. Take a look at the following sentences – the position of almost/only changes the meaning of each one:

The doctors almost treated all the patients (meaning: no patients were treated, despite the doctors’ best efforts)

The doctors treated almost all the patients (meaning: the doctors treated most but not all of the patients)

Only doctors treated the patients (meaning: patients were not treated by anyone who wasn’t a doctor)

The doctors only treated the patients (meaning: the doctors treated the patients; they did nothing else to the patients)

The doctors treated only the patients (meaning: the doctors did not treat anyone who was not a patient).

There's more to life than correct grammar

Readability is more important than correct grammar. Dangling modifiers are sometimes acceptable in the Methods section of a research paper because the reader does not need to be continually told who the subject is. For example:


RNA was extracted from patient tissue using ethanol precipitation.


In this sentence, the gerund (using) is dangling because who or what is extracting the RNA is not specified. To correct this, you would have to introduce a subject:


We extracted RNA from patient tissue using ethanol precipitation.


But your Methods section will be difficult to read if you keep saying ‘we did this….we did that’. And the first sentence is perfectly understandable anyway because the reader knows that the authors have performed the experiments. In any case, they are more interested in how the RNA was extracted than who extracted it. The same is also true for dangling infinitives:


To culture cortical neurons, cortical tissue was dissociated.


This sentence is not grammatically correct because the infinitive phrase (To culture cortical neurons) is dangling. But the reader will easily infer that somebody is dissociating cortical tissue to establish cortical neuron cultures because they are reading the Methods section of a research paper.

Avoid ambiguity

Saying what you mean and avoiding ambiguity are very important when you are reporting your research findings. The tips outlined in this article will help you to specify which words and phrases are being modified in a sentence to make your meaning clear in your next research paper.

Make sure your sentences are crystal clear

Claire Bacon is a former research scientist with professional qualifications in copy editing and medical editing. She edits manuscripts for non-native English-speaking scientists and works as a copy editor for a biomedical journal.

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