Each bibliographic database queries its library of scientific articles in different ways. We have formatted the NHP search filters to take these differences into account and search publications by their associated index terms (i.e., standardized database terminology labelled as topic-relevant) and other aspects (i.e., title, abstract, author keywords) that ensure that new relevant publications are detected. Below are the definitions of each syntax used.

^aNote: Keywords Plus is an algorithm developed by Web of Science that retrieves publications that are broadly related, but lack the original search terms (e.g., detects publications with terms of other mammal species, but no NHP terms). Please note that this algorithm may increase the time necessary to filter search results for directly topic-relevant publications.

Index terms are topic-relevant standardized search terms that are tagged (i.e., indexed) as topic-relevant by each bibliographic source. These terms are found at the beginning of search filters created by filterNHP if they are relevant to the taxonomic group you are interested in. PubMed uses MeSH terms (i.e., Medical Subject Headers) created by the National Library of Medicine (NLM) and are searched using the syntax '[mh]' or '[mh:noexp]'. Similarly, PsycINFO uses the American Psychological Association (APA) Thesaurus of Psychological Index Terms and are searched for via EBSCOhost within the syntax 'DE()'. Web of Science does not have an associated thesaurus. Each bibliographic source organizes index terms into a hierarchical structure by subject category so that more specific terms (i.e., narrow) are nested under more general terms (i.e., broad). Including index terms expands the scope of literature searches and may result in the retrieval of publications that may have gone undetected otherwise.

We created search filters that maximize the number of potentially relevant publications because literature reviews may reach biased conclusions if they are missing relevant publications. Therefore, we included terms that are commonly used to refer to NHPs, but may also reference other nouns. For example, we include the term 'monkey' in the comprehensive NHP search filter, although it may also be used to refer to a 'monkey wrench' or the 'monkey orchid'. As a result, publications unrelated to NHPs may be retrieved. Publications irrelevant to the topic you are interested in can be filtered out during search result screening phase. We encourage users to review the search filters created by filterNHP and adapt them to their own specific needs.

Before combining an NHP filter with a topic search string, researchers must thoughtfully determine and test what topic-relevant terms are necessary to include. Searches conducted in PubMed and PsycINFO should include relevant index terms that can be identified from the Medical Subject Headers (MeSH) database or the APA Thesaurus of Psychological Index Terms, respectively. The topic search string should also include any topic-relevant terms to be searched in the title and abstract of publications (TIAB terms), which primarily retrieve publications that have not received an index term yet. Index terms and TIAB terms are formatted using the syntax of the corresponding source and combined with the Boolean operator 'OR'.

Below we provide an example for a topic search strings on cortisol related studies (index terms are indicated in italics). Note that Web of Science does not have index terms as this platform has no associated thesaurus.

To find publications involving NHPs on a particular topic, search filters from filterNHP and the topic search string should each be surrounded by parentheses and combined together with the Boolean operator 'AND'. Below are examples of an NHP search filter for the genus Macaca combined with the topic search strings for cortisol related studies (see above). Green text indicates the NHP search filter and purple text indicates the topic search string; index terms are indicated in italics.

• Index terms:
  • National Library of Medicine: Medical Subject Headings (MeSH)
  • Radboud University: MeSH in PubMed
• Syntax:
  • National Library of Medicine: PubMed User Guide, Search Field descriptions and tags
  • Radboud University: Search by Word in PubMed
• General help:
  • National Library of Medicine: PubMed User Guide
• Library guides and tutorials:
  • National Library of Medicine: PubMed online training tutorials
  • Radboud University: PubMed Basics tutorial
  • Radboud University: PubMed Advanced tutorial

• Index terms:
  • American Psychological Association: Thesaurus of Psychological Index Terms
Syntax:
• • EBSCOhost: Syntax search tips
• General help:
  • American Psychological Association: PsycINFO Topic Guides
• Library guides and tutorials:
  • American Psychological Association: Databases on EBSCOhost tutorial
  • EBSCOhost: Basic searching tutorial
  • EBSCOhost: Advanced searching tutorial
  • Radboud University: PsycINFO Basics tutorial

• Syntax:
  • Web of Science Core Collection Help: Search operators
  • Web of Science Core Collection Help: Search rules
• General help:
  • Web of Science Core Collection Help: Table of Contents
• Library guides and tutorials:
  • Radboud University: Web of Science tutorial