Musings on the research onion

Many of you will recognise the term ‘research onion’. Disappointingly, this is not a sentient onion that has mastered the skills of research, but is a shorthand reference to a well-known and well-used model showing the various methodological decisions one must make when designing a research project, devised and published by Mark Saunders, Adrian Thornhill and Philip Lewis (2015).

The idea behind the onion diagram is that each layer of the onion represents a decision to be made about your research project. Starting on the outermost layer of the onion, you select your research philosophy, then on the next layer in you select whether you will use an inductive or deductive approach. Moving further into the onion you decide which data collection method will work for your project and decide whether you’ll use just one of these or a combination. In the final layers you decide whether your project will be long term or time-constrained and consider data collection and analysis.

It’s a very popular diagram used in many research methods classes and it turns up in student dissertations a lot, as an illustration of the research process and an aide-memoire of all the stages of a research project’s methodology. It’s a very handy diagram that makes the researcher think about the details of the project, but necessarily stops short of going into the different approaches available for surveys, interviews, etc. and the stages of data analysis as it would then become the world’s largest onion.

The problems with the research onion, for me, are these. First, it is often used out of context by students who do not understand all the terms within it. Second, students often find it confusing and try to join up the words in the diagram that seem to form a straight line from the outermost layer to the centre of the onion, in the mistaken belief that one must take a straight line through the diagram, rather than choose the appropriate option from each layer (probably because they have not read the accompanying text in the book). Third, after seeing it in about 20 dissertations every year for eight years I was frankly bored of looking at it.

So, I challenged my dissertation students one year to come up with an alternative. And to my delight, one of them devised the research rainbow layer cake. This was a fabulous alternative and related to a foodstuff that was instantly appealing to many. The student had labelled each layer of the cake with research philosophy, inductive/deductive approach, data collection method and so on, just as Saunders, Lewis and Thornhill have done with their onion. I absolutely loved the rainbow layer cake and gave the student lots of positive feedback for being so inventive. However, the cake required an arrow at the side to indicate the order in which one should consider each element of the methodology. This was a shame, as it kind of looked as if one would eat a layer cake one layer at a time, which is a bit weird. (Sorry if that’s how you eat a layer cake.) I think this is a fundamental problem with basing research diagrams on foodstuffs – I want the way in which the diagram is used to mimic how one would eat the foodstuff and that isn’t possible. You could say that this is entirely my problem and not a problem with the diagrams, and you would be absolutely right. There’s no way that the research onion or the research rainbow layer cake were designed to mimic the way they would be eaten. That’s just my brain not liking the idea of peeling and eating an onion one layer at a time or eating a layer cake one layer at a time. I know this is my problem, and I always push it to one side when teaching, as I have never found a single other person who has the same problem.

For me it would be much easier to represent the different elements of methodology as a decision tree. This would involve simple decisions leading to more simple decisions with no foodstuffs involved. It would not be a graphical or artistic beauty, but would appeal to my text-based mind, so may appeal to others who prefer text to images.

So I set about devising my methodological decision tree diagram, which I thought would be easy. But no! It really wasn’t easy to make it look simple. And there were lots of decisions to be made about what to include and what to exclude. What I found, in essence, was that it is extraordinarily difficult to condense an entire text on research methods into one simple diagram. But I persevered and send a draft to a colleague, Dr Devi Gill, who also loves methodology, and she sent me some great feedback and some more ideas. Eventually, this is what we came up with. (Apologies if you need a microscope to read it.)

Our diagram is not perfect. For example, it shows only three research philosophies. We mentioned interpretivism, pragmatism and positivism as these are the three most commonly used by our students and colleagues, but we know there are others. But like Saunders, Lewis and Thornhill, who didn’t want to design the world’s largest onion, we didn’t want to design the world’s largest decision tree, so we had to draw a line somewhere. Maybe it would be better to use a whole separate diagram for each research philosophy. Maybe it would be better to have a group of options from which one makes a choice, followed by another group of options and so on, without the arrows showing what is appropriate. What do you think? Do you have any comments on our new diagram? Do you have your own favourite? I’d love to know!


Saunders, M., Thornhill, A. and Lewis, P. (2015) Research Methods for Business Students, 7th edition, Harlow: Pearson.

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