When we’re reading, some texts just flow, rolling out ideas in a smooth sequence. Others seem to lurch from sentence to sentence as if there was a problem with the clutch. Texts that flow are easier to understand, because moving smoothly from sentence to sentence requires that the links between the ideas be explicit. We can therefore follow the author’s logic from beginning to end without backtracking or rereading.
Our sense of logical flow comes from the links between sentences, and sentences that flow have one key structural feature: the last part of one sentence is conceptually linked to the beginning of the next. In other words, the last few words of one sentence are similar to those that begin the next one.
The first step in making a text cohesive is to order the topical/contextual/familiar information and new/important information, like I discussed here. Once the context or familiar information is placed at the beginning and the important or new stuff is at the end, your sentence will look something like this:
At the end of that sentence, we can consider that the new information is now familiar: the reader has seen it. A flowing text uses that new information as a basis for introducing a second piece of new information in the next sentence, and then that now-familiar information is used in turn to introduce yet another new point. This creates a chain of sentences that looks like this:
This is the principle of cohesion: each sentence “sticks” to the next one, because the end of one and the beginning of the next are clearly related.
Here is an example. The following paragraph is from an editor’s introduction to a special issue of a journal. The goal is to introduce Malinow’s review article, and underlining the sentence junctions shows why the paragraph doesn’t flow.
Synapse dysfunction and loss are hallmarks of Alzheimer’s disease (AD) and may predate the massive cell loss that characterizes late stages of the disease. Beta-amyloid (Abeta) appears to have detrimental effects on synapses and this activity is often invoked as a pathogenic mechanism contributing to the cognitive impairment of AD. Malinow reviews the evidence that Abeta impairs synapse function and plasticity and that Abeta synaptotoxicity is mediated, at least in part, by NMDA receptors.
The two sides of both sentence junctions contain information that isn’t clearly linked to each other at that point in the text. This means that when the reader starts the second sentence, they don’t know how it’s related. They must read to the middle or end of the sentence to understand the beginning. For example, we don’t know until halfway through the sentence why we’re talking about beta-amyloid, or why we might be interested in a guy named Malinow.
Sentences that are not cohesive create gaps in the logical flow, and means the reader spends a few seconds per sentence being lost. If your sentences are very complex, a lack of cohesion may mean the reader is lost for a few minutes. Over an entire paper, a few seconds or minutes per sentence add up to a lot of time spent confused.
Reordering each clause or sentence to put context before new information can often fix the problem. In this revision, I’ve reordered the information that appeared in each sentence, putting the context first, and related information at the sentence junctions:
Late stages of Alzheimer’s disease (AD) are characterized by massive cell loss, which may be predated by synapse dysfunction and loss. Detrimental effects on synapses are caused by beta-amyloid (Abeta), and this activity is often invoked as a pathogenic mechanism contributing to the cognitive impairment of AD. The evidence that Abeta reduces cognition by impairing synapse function and plasticity and that Abeta synaptotoxicity is mediated, at least in part, by NMDA receptors, is reviewed by Malinow.
In this version, the first part of each sentence is something we’ve heard about just before: synapse dysfunction in the second sentence, and beta-amyloid’s effect on synapses in the third. This means we can read this text from beginning to end without falling into logical gaps.
So, to diagnose the logical flow of your sentences, look at the junctions between them. Is the first part of each sentence familiar information? Is the end of one sentence clearly related to the beginning of the next?
Patricia Gongal works with researchers to improve the structure, clarity, flow, and style of their scientific writing, and has lots of opinions about science and academia.