How to Structure a Scientific Article: OCAR – Challenge

In our previous article, we outlined how to craft a captivating opening for your scientific paper. The next critical component in the structure of your scientific article: the ‘Challenge’.

The challenge of a scientific article could be either a hypothesis or a question. This depends on how much is known and also on the field. Biology often uses hypotheses in the form of questions, such as “Do hummingbirds prefer red flowers”. Here the reader assumes that this is going to be tested. Other fields vary but most tend to use a question: “What is the rate constant for a chemical reaction involving methane and hydroxyl radicals?”

Understanding the Importance of the Challenge

The challenge in a scientific article defines the central problem or question addressed by your research. It outlines the knowledge gap your work aims to fill or the hypothesis it seeks to test. By establishing a clear challenge, you give your readers a framework to understand the purpose and potential impact of your work.

One thing to make sure is that you don’t try to answer the question here. That is what the rest of the paper is for. A good place to start is to ask yourself “What was the original question that led me to do this research”.

Formulating a Strong Challenge

A well-articulated challenge should effectively pose a question or present a hypothesis that your research seeks to answer or test. The formulation of the challenge may vary depending on the field. For instance, in biology, the challenge might be stated as a hypothesis, such as “Hummingbirds prefer red flowers”. In other fields, it may be presented as a direct question, like “What is the rate constant for a chemical reaction involving methane and hydroxyl radicals?”

How to Structure the Challenge

The challenge should be framed in a manner that puts the focus on the question or hypothesis, not just the data you plan to collect. Here’s a simple formula that captures this concept: “To learn this, we did that.” This format first presents a question or a hypothesis and then outlines the approach to answer it.

Consider the following example:

“We hypothesized that hares control the structure of shrublands by foraging on shrub seedlings in the gaps between mature plants. If true, hares act as keystone herbivores by maintaining these gaps, in which grasses can outcompete shrub seedlings. We tested this hypothesis by following hare movement to determine where they eat and by analyzing their feces to determine what they eat.”

In this example, the authors clearly define their hypothesis and the methodology used to test it, providing the reader with a clear understanding of the study’s focus. This is an excellent example of a challenge.

Let’s practice!

Look at the following challenge. What is wrong with them and/or how can we improve them?

Some T-cells may be anergic — that is, unable to proliferate after being restimulated with an antigen. Some anergic T-cells are unable to link to the T-cell– antigen-presenting cell (APC) interface. Here we examined the structural characteristics of anergic mouse T-cells and we tested their functional response to being rechallenged with antigen-loaded APCs.

This challenge does not tell us anything about what the research question is or what ultimate knowledge we hope to gain. The first sentence is a definition and the second is a characteristic of these kinds of T-cells. So? What is the problem? Why do we care about this?

The next part then starts with “We examined the structural characteristics…” That is great, but why? What are we trying to learn? An easy fix could be: “To determine what causes mouse T-cells to be anergic, we examined …”


Crafting a clear and engaging challenge in your scientific article is key to capturing your reader’s interest and providing a framework for understanding your research.

For the challenge, the biggest problem writers have is focusing on the question or hypothesis and not on the objective. “Our objectives were…” focuses on the information you will collect instead of the knowledge you hope to gain. The reader has to determine what the question is if there even is one. Forcing the reader to figure out the question you want to test makes them lose concentration and sometimes interest as well. If they lose interest, they might stop reading, which is the last thing we want. Objectives come afterwards to show how you go about tackling the challenge.

In our next article, we will explore the ‘Action’ phase of structuring a scientific article.

Click here to read more about structuring articles.

Interested in learning more about Scientific English? You can read a brief post on the History and Use of Scientific English here. More posts on Scientific English are available on the Scientific English page.

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