Have you ever wondered what the difference is between a keyword and an index term, and how they can aid your search? What are classification codes, and how does this all relate to MeSH terms? This post will demystify the four types of vocabulary you see in APA PsycInfo®.

Keywords (also called Key Concepts or Identifiers) – Individual words, key concepts, or brief phrases that describe the document’s content. The list of keywords for an article is often provided by the author or publisher, though sometimes it is created by APA staff. There is no pre-existing list of keywords that authors, publishers, or APA staff choose from.

Keyword searching is a good fit for researchers who are new to a topic, and want to get the full scope of what is available. Keyword searching is most similar to the searching you may do on the internet, because keywords are often in natural language or layman’s terms. In addition, you do not need to select or know terms from a pre-existing list, as you do for the following three types of vocabulary.

Index Terms (also called Subjects or Subject Headings) – Index terms are also single words or brief phrases that describe the document’s content, but they are chosen from a pre-existing list (also called a controlled vocabulary). For the APA databases, that list is the Thesaurus of Psychological Index Terms®, which includes more than 8,400 terms. APA staff typically choose about six index terms for each document. You can use the thesaurus tool, linked from the APA PsycInfo search page, to search or browse index terms alphabetically or by topic.

Index term searching is a good fit for the focused researcher, who has identified their best term(s) and now wants to quickly find all of the items about a particular concept. With the wide variety of concepts and vocabulary used in the psychological literature, searching for and retrieving records about specific concepts is virtually impossible without the controlled vocabulary of a thesaurus. It provides a way of structuring the subject matter in a way that is consistent among users (e.g., searching for Dysphoria, Melancholia, and Depression can all be achieved by searching the term “Major Depression”).

Classification Codes (also called APA PsycInfo Classifications) – Each classification code is a descriptive term plus a corresponding numerical code. Like the index terms, there is a pre-existing list, or controlled vocabulary, of APA PsycInfo Classifications, which represent subfields of psychology and the behavioral sciences. There are 22 major classification categories, and 135 classification subcategories. APA staff typically choose one Classification for each record. (There is a separate list of APA PsycTests Classifications, which identifies the general area of psychology that the measure is designed to assess.)

Classification searching is good to use in tandem with keywords or index terms. You can think of classifications as representing “buckets” of different types of research in APA PsycInfo. Using them can be helpful if you’re searching for a word that means different things in different schools of psychology. For example, if you are searching for the keyword “drone,” you can choose your classification to be either Animal Psychology or Military Psychology, to capture the definition of drone you are using. Or, if you are searching for the index term “Alzheimer’s Disease,” you can choose your classification to be either Psychopharmacology or Nursing Homes and Residential Care, to match the perspective of your research.

MeSH – Medical Subject Headings are a controlled vocabulary that is maintained by the National Library of Medicine for their PubMed database. About 30% of APA PsycInfo records also appear in PubMed, and for these records APA adds the MeSH terms from PubMed to the APA PsycInfo record.

MeSH searching is good for people who are researching medical or neuroscience topics, or who are already familiar with the MeSH vocabulary. You can learn more about MeSH, and search for MeSH terms, at the NLM website.

MeSH terms are arranged into a hierarchy, and when searched on PubMed any narrower terms are automatically included. For example, on PubMed a MeSH term search for Aggression will automatically include the narrower MeSH terms Agonistic Behavior and Bullying. This hierarchical structure is not reflected in the MeSH terms included in APA PsycInfo records.

Consider what type of searching you’re doing, and what database you’re using, to help you choose the best vocabulary for the job. APA PsycInfo records, along with the records in APA PsycArticles® and APA PsycBooks®, have all four types of vocabulary – Keywords, Index Terms, Classification Codes and MeSH. APA PsycExtra® and APA PsycTherapy® records have Keywords, Index Terms, and APA PsycInfo Classifications.

APA PsycTests® records have Keywords, Index Terms, and their own set of APA PsycTests Classifications.

Related Resources

APA PsycInfo Expert Tip – Classification Codes

Using Classification Codes on EBSCO

How (and Why) to Use the APA Thesaurus When Searching APA PsycInfo on Ovid

Using the APA Thesaurus to Find Relevant Articles on a Topic