Engineer's Guide to the Library

Using the keywords and synonyms from step 2, you create search strings (what you type into a search box) and use them to search in the databases you identified in step 3.

Based on the results, you will then modify your search terms, removing or adding terms, and use these revised search strings in the same databases, or different databases. You may need to repeat this process multiple times before you find relevant articles.

Creating Search Strings

The keywords and synonyms you created in step 2 can be combined in multiple ways to create search strings, using boolean operators (see box below). There is no one right way to create a search string; it's largely a matter of trial and error. If you use a search in a database and get no results, you probably want to remove terms from your string to make it more general. If you get too many results, you may want to add terms to make it more restrictive. And if you are getting results but most of them aren't relevant, you may need to use different terms.

If your topic has three keywords (keyword1, keyword2, and keyword3), and each keyword has two synonyms (synonym1a and synonym2b, etc.), some possible search strings to start with are:

• Simple string combining all keywords: keyword1 keyword2 keyword3
• Complex string using all synonyms: (keyword1 OR synonym1a OR synonym1b) AND (keyword2 OR synonym2a OR synonym2b) AND (keyword3 OR synonym3a or synonym3b)

Revising Searches

After you use a search string in a database, look over the results. Were there no results, only a few, or and overwhelming number? Scan the first page of results, looking at the titles and abstracts. Do they seem relevant to your topic?

Based on what you see, you will usually need to modify your search. Here are some tips on how to do so:

• If there are no results or only a few, try removing search terms to make your search more general.
• If many of the results aren't relevant, think of additional terms you could add to your search.
• If you find any relevant results, look at the terms used in the title, abstract, and and subjects the database assigns to them. These may give you additional search terms to try you hadn't thought of initially.
• Most databases include refinements on the left side of search results, allowing you to limit the results by date, subject, type, etc. These refinements can be useful in narrowing down your search.
• Many databases provide a list of related articles when you are looking at an article record. When you find an article that might be relevant, look for such a list to suggest other articles that might be useful.

As you conduct your iterative searches, whenever you find an article that looks like it might be useful, take a note of it (ideally, capture it with a bibliographic manager (also known as a citation manager) so you can read it and use it later.

Expanding Searches

Sometimes a search produces no usable results, even after revising the search and using synonyms. This problem is especially common when searching on a particularly narrow and specific topic. Sometimes it means that you need to keep trying different search terms, or search in a different database. But it may mean that there hasn't been any significant research published on your exact topic.

In this situation, it is sometimes easier to modify your topic to one where more research has been done. But if that isn't possible, or you are particularly invested in the topic, it is still usually possible to find relevant research papers. A topic is usually at the intersection of several subjects, and even if you can't find research on that exact intersection, you can usually find useful research on the component parts.

In the example of timing of rewards for long-term engagement in video games, assuming there are no relevant papers on that exact topic, you could search for articles on engagement in video games (leaving out the question of rewards and timing), or on rewards in video games (leaving out the question of engagement), or just on video games in general. Articles on these related topics are likely to have a bearing on the more specific topic.

This expanded search strategy is useful even when you can find research on your exact topic. If you look at the references in a paper, you will find that while they may cite some articles on more or less the same topic as the paper, they also usually cite many articles on related, relevant research that is not an exact match.

While every database has its own rules for how it interprets search strings, these tricks work in most of them. If you find yourself using a particular database a lot, it is worth looking at its Help page to find what tricks work for that database.

• AND: Use "AND" between words in your search when you want to find things that include both of them. keyword1 AND keyword2 will only find results that have both keyword1 and also keyword2.
• OR: Use "OR" between words when you want either one or the other (or both). It is especially useful when using synonyms. keyword1 OR synonym1 will find results that have at least one of the two terms.
• NOT: Use NOT before a word when you want to make sure the word doesn't appear in the results. Some databases use a symbol instead of "NOT", so it is worth check the Help page.
• Parentheses: Use parentheses to group ANDs and ORs. (keyword1 OR synonym1) AND (keyword2 OR synonym2) will return results that have at least one of keyword1 and synonym1, and also have at least one of keyword1 or synonym2.
• Quotes: Use quotes around a phrase to search for words as a phrase, instead of individual words. human factors will find results that have the word "human" and the word "factors" anywhere in them, possibly far apart, while "human factors" will only find the two words next to each other as a phrase.

The student tried multiple search strings initially, including a search that just used all their keywords; another, more complex search that included most keywords and synonyms, and another one that was somewhere in between. 

• optimal timing rewards computer game long-term engagement
• (optimal OR best OR ideal) AND (timing OR frequency) AND (reward OR "positive feedback" OR "leveling up") AND game AND ("long-term" OR extended OR persistent) AND (engagement OR use OR enjoyment)
• (timing OR frequency) AND rewards AND game

Using these searches in the ACM Digital Library, the student found the first search returned over 600,000 results, while the second search found over 70,000, and the third over 10,000 (in ACM, when you search for a string of words with no connectors, it treats it as if there was an "OR" between each word, and returns everything that has any of the words).

Scanning the results, the student found that some of the articles in each of the searches seemed relevant to their interests, with the third search giving the best results.