Advice for writing the PhD statement of purpose

All PhD applications have you write a statement of purpose (SoP). This is a personal perspective on what I look for in one.

tl;dr

At the bottom of this page, I list key principles to keep in mind when writing your Statement of Purpose, but, before I get there, I walk through a lot more specific advice.

Preamble

Don’t have this be the first or only advice you read

There are many guides online about what to include in your SoP, both from individuals and from departments or institutions. You should find them and learn from them, if not follow their advice exactly. I particularly like this advice from Stanford; even though it’s from a different field, I think all of its points are important and applicable. This guide from MIT offers a useful structure and tips, as does this UMD “Algorithm”. You can find even more tips on this Berkeley page. There are multitudes of others.

In addition, many current and past PhD students have posted their SoPs publicly. Try to find examples from top schools and read through them.

Keep in mind that my advice is specific to me

Regardless of where you apply, your application will be read by multiple people, each with their own priorities. Don’t overfit to me; instead use my advice below as one of many inputs you consider while crafting your statement.

Explain your goals

One of the things your readers will try to glean from your statement is why you’re applying to a PhD program.

Mention your motivations

It’s almost a trope for SoPs to talk about coding since early childhood. For me, it doesn’t matter much whether you’ve been programming since the age of five, or if the first code you wrote was in college (or later!). But I am genuinely interested in learning about what drives and motivates you. What do you care about? This can help me understand why you’re pursuing a PhD and how we can best work together.

Your motivations are important, but this is not something you need to dwell on. Space in your SoP is at a premium, so I wouldn’t advise spending more than a couple of sentences on this.

Be honest about your objectives

Besides describing your high-level motivations, your statement should also speak to what specifically you intend to do with your PhD. If you’re not exactly sure yet, that’s totally fine! Also, there are plenty of valid reasons for pursuing a PhD. You don’t have to say that you’re in love with research or want to become a professor. I care about helping you meet your goals, whatever they are, so it’s important for me to understand your objectives. Once again, this is not the most important part of your statement, so a sentence or two will suffice.

Show that you understand what you’re getting yourself into

One of the most important things you can demonstrate with your SoP is that you understand what a PhD is — a research-oriented degree, very different from a bachelor’s or master’s — and what that entails. This will hopefully come across both when you write about your motivations and your experience.

This isn’t something you need to dedicate separate space to in your statement. To a large extent, it’s a matter of framing and what you choose to focus on. For example, a statement where the applicant dedicated a lot of space to what classes they wanted to take would signal that they may not be aware that the bulk of the PhD is dedicated to research efforts.

Illustrate your experiences

A major part of your SoP will be dedicated to your prior experiences. It’s worth carefully considering what to include.

Showcase relevant experiences

Since you’re applying for a research position, the most effective way to demonstrate that you know what research is all about is by actually having research experience. If that’s the case, you should be sure to explain it in your SoP.

If you haven’t yet participated in research, that’s okay! When describing your experience, focus on projects that are most similar to research: open-ended, with uncertain outcomes, where you were responsible for setting the direction. You might also consider mentioning how you know that you want to pursue research. Did you observe someone else do it? Talk to someone about it? Read something?

Highlight the parts that aren’t in your résumé

Your CV/résumé will already list your experiences. Repeating what’s already written there is not a good use of space. Instead, use the SoP as an opportunity to elaborate on or clarify these experiences, or talk about ones that aren’t included but you think help complete the picture. In all cases, be specific: make sure that I’m able to understand what you actually did. Claims that are vague or sound exaggerated will only make your application look worse.

Clarify your role and creative contribution

When describing individual or group projects, don’t focus only on the outcomes. (These should already be evident in your CV.) Instead, I find it valuable to know how that was achieved. Who came up with the initial idea? Who did what part? What were the challenges you encountered and how did you overcome them?

Explain how you learned rather than what you know

Industry résumés often list specific technical skills you possess. This is not expected in an academic CV. Whether or not you choose to include them in your CV, listing them in your SoP is not useful. Instead, consider talking about how you acquired them. Did you learn them on your own, in class, at work, or as part of some extracurricular activity?

Even more important than how you acquired these skills is your vision for how you will use them as part of your PhD. You might leverage them directly (such as statistics or programming) or indirectly (if they will inform your research topics or interests).

Show technical depth

Your SoP provides a great opportunity to show that you’ve reached technical depth in the areas that you’ve worked in. While you shouldn’t go into all the nitty-gritty details — you don’t have the space for that — you can demonstrate your expertise by including some carefully chosen examples. Another place where you can achieve this goal is when you discuss your proposed research.

Demonstrate research fit

In addition to your past experiences, a key part of your SoP will be dedicated to explaining what you want to focus on in your PhD. Research fit is very important to me personally and is also what other faculty are likely looking at to decide whether you’re a match for their labs. Rather than just assuring me that you care about the same things that I do, the SoP offers you an opportunity to demonstrate it.

Show that you know the field

After reading your SoP, I should have a sense that you have a pretty good understanding of what the research field you’re interested in is about, such as what problems it’s trying to solve, what methods researchers use, and what outcomes are realistic.

Provide examples of research directions

In particular, it’s a good idea to include an example or two of a research direction you would be interested in pursuing as part of your PhD. Don’t worry: you’re not committing to work on the topic you write about. Rather, what you’re showing here is, again, your understanding of the field. For example, proposing to work on a solved problem is not a good look. You’re also showcasing your ability to independently generate original ideas — something that you’ll need to do a lot of during your PhD.

Be specific and realistic

When describing research you’re interested in, it’s a good idea to list specific research questions you’d want to work on and provide a brief explanation of how you’d tackle these projects. Again, you’re not committing to anything, but this level of detail will help showcase your understanding of research and the field you want to enter.

Polish your writing

After you’ve written your SoP, take the time to polish it and any other materials you’re submitting. Check them for spelling and grammar issues. If you’re not a native English speaker but have access to one, consider consulting with them. Otherwise, there are online tools (including free and open-source ones!) that can highlight grammar or style issues.

This is not because I expect your language to always be perfect. It’s because there will be times (like when we submit a paper) that we’ll want our output to be as polished as possible. This is your opportunity to show that, when that time comes, you will be able to meet these standards independently and without micromanagement.

Here are some specific things to look out for:

Don’t use LLMs

Large language models like ChatGPT can be useful in certain contexts (including, for some people, in their writing process), but I would strongly discourage you from drawing on them for your SoP.

LLMs tend to output text that sounds generic and often lacks personality (and substance). I want to hear your unique voice. If the text sounds inauthentic, it lessens the impact of what you have to say. Worse, it makes the reader question the veracity of the content. If the ideas in your statement don’t seem like they are actually your own, you will come off poorly, no matter how strong the rest of your application might be.

Moreover, in any papers we write together, I’ll be old-school and insist that we write them from scratch. I would prefer to understand your natural writing style now rather than discover it later. If I discover, during our interview, that there is a big difference between your spoken and written language, this is also something that is likely to count against you.

Key principles

To conclude, here are some higher-level principles to keep in mind as you write or edit your statement:

  • Understand that an SoP is a job application to become a researcher.
    Write your entire essay with this perspective. On the other side, your reader is a professor deciding whether you are a good fit for the role of research assistant.
  • Including specific examples is better than speaking in generalities. This is one way to manifest the often-cited principle to show don’t tell.
  • Don’t include redundant or irrelevant information. If it’s already elsewhere in your application, your SoP can add relevant context but shouldn’t simply restate things. With all new information that you’re including, consider: what purpose is this serving?