Searching by topic
The Bio 1B Research Skills Assignment uses the database BIOSIS Previews; however, most of the search strategies discussed here also work in other databases.
A. Starting your search: Developing keywords from a topic
To find articles on a topic you must craft a search strategy, which involves the following steps:
- Break your topic down into its main concepts which will be your search terms (keywords).
Topic: the impacts of climate on the migration of butterflies
Concepts/Search terms: climate migration butterflies
Don't include common words such as "impacts," "effects," "role," "of," "on," or "the." These occur in almost every article and so won't help you to find the specific articles that are relevant to your topic.
- Choose an appropriate database in which to begin your search. You may find that you need to use more than one database; see Biological Sciences Databases for a descriptive list.
Note for the Bio 1B assignment: You will use BIOSIS Previews.
B. Building your search using AND, OR, and parentheses
- will retrieve results that include ALL of the terms
- should be used to join terms describing different concepts
- Example: migration AND butterflies
- This search will retrieve all records for articles, book chapters, conference proceedings, etc., that include both the term migration and the term butterflies.
- narrows a search to retrieve fewer results
- Example as of Spring 2020:
- migration = 305,800 results (all records that include the term migration)
- migration AND butterflies = 800 results (all records that include both the term migration and the term butterflies)
- in most databases and search engines, including AND is optional. Terms separated by a single space will be searched as though they are separated by AND.
- Example: The following searches are interpreted in the same way by database search engines:
- climate migration butterflies
- climate AND migration AND butterflies
- will retrieve results that include ANY of the terms
- should be used to join terms describing related concepts or synonyms
- Example: climate OR temperature
- This search will retrieve all records for articles, book chapters, conference proceedings, etc., that include either the term climate or the term temperature
- broadens a search to retrieve more results
- Example as of Spring 2020:
- climate = 215,500 results (all records that include the term climate)
- climate OR temperature = 1,355,400 results (all records that include either the term climate or the term temperature)
- A common error: Using OR to join terms that don't express a similar concept will retrieve irrelevant results:
- Less effective: climate OR butterflies
- This search will retrieve all records that include the term climate (whether or not they have anything to do with butterflies) as well as all records that include the term butterflies (whether or not they investigate climate effects).
- More effective: climate OR temperature
- This search will retrieve all records that include either the term climate or the term temperature.
Parentheses: if you're using both AND and OR in your search, use parentheses to group together terms connected with OR.
- Less effective: climate OR temperature AND migration AND butterflies
This search will retrieve every record that includes the term climate, whether or not it has anything to do with the migration of butterflies, as well as every record that includes all the terms temperature, migration, and butterflies.
- More effective: (climate OR temperature) AND migration AND butterflies
This search will retrieve records that include either the term climate or the term temperature, but only when either term occurs with both the terms migration and butterflies.
A note on capitalization:
- OR is not "or": It's very important when you use the operators AND and OR that you capitalize all their letters. If you enter them in lower or mixed case many databases and catalogs will read them as the words "and" and "or," and will ignore them. The words "and," "or," "the," "is" and many other common words are known as "stop words" because databases and catalogs skip them when they are parsing the search string.
Implied ANDs: This can have major effects on your search. Many databases and catalogs use an implied AND: if two terms are not combined with a specified operator, AND is assumed. Thus, for many databases and catalogs the two searches on either side of the equals sign are considered equivalent:
So when you use a lower-case "or" and it is ignored, many databases and catalogs will insert an implied AND between the terms:
- Example: climate migration butterflies = climate AND migration AND butterflies
Instead of searching for resources containing either the term climate or the term temperature, the database or catalog will search only for resources containing both terms, changing the results of your search.
- Example: (climate or temperature) and migration and butterflies = (climate AND temperature) AND migration AND butterflies
C. Narrowing a Search
If you've retrieved too many irrelevant records, these strategies may be helpful in refining your search:
D. Broadening a Search
If your search has retrieved too few results, these strategies may be helpful in retrieving more results:
E. Combining strategies
Here are the number of results retrieved by performing a topic search in BIOSIS by combining these search strategies (the number of results is current as of January 2020; the numbers will change with time as articles are constantly being added to the database):
- It's very important when you use AND and OR that you capitalize them. If they are entered in lower case many databases and catalogs will read them as the words "and" and "or" and they will ignore them. The words "and," "or," "is," "to," "the," and many other very common words are called "stop words," because databases and catalogs skip them when they are parsing the search character string.
This can have odd effects on your search, because many databases and catalogs (as well as Google) use implied ANDs when no other operator is used to combine terms.
- Adding additional concept terms with AND (see Building a search above)
- Phrase searching
Enclosing two or more words in quotes will search for those words as a phrase.
A common error: Enclosing too many words in quotes. Only words that almost always occur together should be enclosed in quotes.
- Example: "climate change" will retrieve all records in which the words climate and change occur in direct sequence.
- Less effective:
- "primary production in tropical rainforests"
- More effective:
- "primary production" AND "tropical rainforests"
- Applying limits
Most article databases provide options to limit searches by various criteria. In BIOSIS, it's possible to limit searches by:
All of these options are available in the "Refine Results" sidebar, which is visible in the results screen after you've done an initial search in BIOSIS.
- Document Type (article, book chapter, etc.)
- Literature Type (such as literature reviews... learn more)
- Major Concept (Ecology, Behavior, etc.)
- Taxonomic Data
- Adding synonyms or related terms with OR (see Building a search above)
You can broaden a search by using truncation to find different forms of a search term.
Some words shouldn't be truncated:
- Example: If migration is one of your search terms, you would want to retrieve articles that include the following forms of the term:
Find the last letter that is common to all of the different forms of the term, and after it place the wildcard character (in BIOSIS Previews and many other databases, an asterisk (*)):
Beware: If you truncate incorrectly, you will either miss relevant results, or retrieve irrelevant results:
- migratory, etc.
- migrati* will miss migrate, migrated, migrates, etc., which are all relevant.
- migra* will retrieve migraine, which is irrelevant.
In these cases, using OR is more effective: (gene OR genes OR genetic OR genetics)
- gene* will find genetic and genes, but will also find general, generally, etc.
- ant* will find ants, but also anthropology, anthropological, anterior, etc.
Truncation can be applied to more than one search term, if appropriate.
- climate AND migration AND butterflies: 66 results
- Adding a related term with OR:
(climate OR temperature) AND migration AND butterflies: 114 results
- Truncating migration to capture other forms of the word:
(climate OR temperature) AND migrat* AND butterflies: 151 results
- Truncating other keywords (if appropriate):
(climat* OR temperature*) AND migrat* AND butterfl*: 246 results
- Phrase searching:
("climat* change" OR temperature*) AND migrat* AND butterfl*: 129 results
- Please note: Generally the term change would not be included in a search, but in this case it is part of the phrase "climate change"