OCAR, ABDCE, & LDR: 3 Structures for Scientific articles

If you want to improve your writing, the first thing to so is understand how scientific articles are structured. In my Ultimate Guide to Scientific Writing, I’ve already explained how scientific articles tell a story and detailed the structure of that story. However, one format does not fit all. Different journals or scientific institutions (for grant proposals) require different structures.

In this post, we’ll look at three common structures used in scientific writing: OCAR, ABDCE, and LDR. By familiarizing yourself with these formats, you will improve the quality and impact of your articles and make your writing process easier.

1. The OCAR Structure

The OCAR structure is the classical structure of most books, tales, movies, and scientific articles. OCAR stands for Opening, Challenge, Action, Climax, and Resolution. It’s the simplest and most logical structure, as each part leads to the next.

Illustration of the OCAR structure in scientific articles.

O like Opening

The OCAR structure starts with an opening introducing the characters and their setting. In a scientific article, the “character” is the research topic. It can be a disease, a molecule, a physical reaction, a historical event, or a psychological process. The “setting,” also called the niche in scientific writing, is the background information about the research topic provided in the introduction.

Just like an exciting film introduces its main character compellingly, the initial paragraphs of a scientific article should highlight the research topic’s significance and outline existing knowledge in the field (see our detailed post on openings).

C like Challenge

In OCAR stories, once the storyteller introduces the characters, a challenge arises that they must overcome. In a detective story, the challenge may be solving a murder; in a romantic comedy, it is to find love or happiness; in an action movie, the challenge consists of defeating the bad guys… The challenge is essential to any story because it creates the tension that motivates the action and entices the reader to continue.

In a scientific paper, the challenge is the problem that the research aims to solve. Just as a good story involves a compelling character facing a daunting challenge, good research addresses a relevant problem within an important topic.

A like action

To address the challenge, the main character in a story takes action. The action consists of events forming 80% of the story. Some events are expected, while others surprise readers, keeping them engaged and invested.

In scientific papers, the section depicting the material and the methods is the story’s action. It details how the researchers conducted their studies or experiments to tackle the research problem described at the previous level. There’s no standard structure for the methods section, but a useful tip is to consult similar articles in your target journal and adopt their layout, which works in 95% of cases.

C like climax

In OCAR stories, the action culminates with a climax scene. The climax in a story is the intense moment when everything falls into place: secrets are revealed, misdeeds are exposed, or unexpected twists occur.

In a scientific paper, the climax scene is the results section, where you present the culmination of the research effort and confirm or refute the hypotheses. There’s no set structure for the results section; in doubt, consider drawing inspiration from articles with the same methodology. The structures of scientific articles are generally not very creative. Research sections based on the same methodologies often use exactly the same structure.

R like resolution

OCAR stories conclude with a resolution that provides closure. In a movie, it can be a joke, a long kiss that promises love for eternity, or a comforting “Let’s go home!”

In a scientific paper, the resolution is provided by the discussion. The discussion recaps the research niche and findings, addresses how results impact the topic, notes limitations, proposes future research, and concludes by underscoring the study’s overall contribution.


OCAR is the classic structure of books, stories, films, and scientific articles. If you’d like to delve deeper into each element, I recommend you read this post. And if you’re wondering why it’s called OCAR and not OCACR, well… I don’t have an answer, except that OCACR is really hard to pronounce, and I’m glad I don’t have to do it every time I teach scientific writing.

OCAR is the simplest and most logical structure, as each part leads to the next. But as the world of storytelling, both in movies and scientific articles, continues to evolve, alternative structures like ABDCE have emerged and become increasingly popular.

2. The ABDCE structure

The ABDCE story structure has gained in popularity in recent years. ABDCE stands for Action, Background, Development, Climax, and Ending. Unlike the OCAR structure, the ABDCE structure kicks off with an intense action scene, instantly capturing the audience’s attention.

Structure your papers like a James Bond movie

Many James Bond films use the ABDCE structure by opening with a dramatic scene.

For example, Spectre begins with Daniel Craig tracking down an assassin during the Day of the Dead parade in Mexico City (you can watch the scene here). Viewers don’t know why James Bond is trying to kill this guy, but the action is so intense that they are nonetheless captivated.

Bridging Hollywood to Academia

This dynamic approach isn’t just reserved for Hollywood blockbusters. Scientific papers sometimes adopt the ABDCE structure too. They might start with a brief summary of the methods and results or use an illustrative example, short story, or quote to evoke emotion in the readers.

Psychologist Jonathan Haidt, who studies moral judgment, begins one of his papers with the provocative story of siblings Julie and Mark deciding to make love, using this example to illustrate that moral intuitions are driven by emotions rather than reason. By employing the ABDCE structure, he effectively captures the reader’s attention from the outset (see here and here for other examples of scientific articles following the ABDCE structure).

You will find the ABDCE structure in various scientific articles, theses (Ph.D., master’s, bachelor’s theses), and grant proposals. Grant proposals often start with a highlight of the main idea, followed by the traditional background, detailing the research topic, niche, and problem.

From a narrative perspective, the ABDCE structure is more complex than OCAR and may be difficult to follow (I don’t know for you, but I always struggle to understand the action in James Bond movies). However, the intense action can still make it compelling, particularly for impatient audiences who need to be immediately hooked.

3. The LDR structure

The LDR story structure stands for Lead, Development, and Resolution. This structure is characterized by a concise lead section that encapsulates the opening, challenge, and solution in as little as one sentence. The development constitutes the main body of the story, followed by a brief resolution. Journalists favor this structure because they need to capture readers’ attention quickly and convey their message efficiently.

In academia, high-impact journals like Nature or Science often use the LDR structure for their short-format articles aimed at a general audience (you can see an example here). These journals receive numerous submissions. Therefore, Authors need a strong lead to persuade editors to review the paper. Including clear illustrations can also help convey the message succinctly.

An iconic example of LDR structure

Watson and Crick authored the iconic 1953 Nature paper titled “Molecular structure of nucleic acids” using the LDR structure. The article unveils their discovery of the DNA double helix, and indeed the lead sentence reads:

We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A.). This structure has novel features which are of considerable biological interest.

This lead goes straight to the point, highlighting the character (the structure of DNA) and its significance. The rest of the remarkably short paper presents the arguments for the double helix and concludes in a single sentence.

Choosing the Right Structure

When deciding which structure to use for your scientific paper, consider your audience and the outlet. For patient readers, the OCAR structure allows the story to unfold naturally. For less patient readers, the ABDCE structure provides an immediate taste of action, while the LDR structure caters to the least patient readers with a condensed message.

It’s essential to adapt your structure to the outlet, whether it’s a journal, grant proposal, thesis, or something else. Certain fields of research or specific journals may have unique structural requirements. It’s crucial to make the reader’s task as easy as possible by providing clear organization and meeting their expectations.

In sum…

Structuring scientific papers can be challenging, but understanding the story elements and employing the OCAR, ABDCE, or LDR structures can make your writing process smoother. By considering your audience and the outlet’s requirements, you can tailor your paper’s structure to make it compelling and resonate with your readers. Remember, the right structure is essential in telling a captivating story that will leave a lasting impression on your audience.

How to write your introduction + template

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Writing a good introduction is essential to getting your paper published in a top journal and captivating your readers. It’s essential… and challenging! With this template for writing your introduction, you will find:

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