Background: Research in decision-making has identified heuristics (rules of thumb) as shortcuts to simplify search and choice.
Objective: To find out if GPs recognize the use of rules of thumb and if they could describe what they looked like.
Methods: An explorative and descriptive study was set up using focus group interviews. The interview guide contained the questions: Do you recognize the use of rules of thumb? Are you able to give some examples? What are the benefits and dangers in using rules of thumb? Where do they come from? The interviews were transcribed and analysed using the templates in the interview guide, and the examples of rules were classified by editing analysis.
Results: Four groups with 23 GPs were interviewed. GPs recognized using rules of thumb, producing examples covering different aspects of the consultation. The rules for somatic problems were formulated as axiomatic simplified medical knowledge and taken for granted, while rules for psychosocial problems were formulated as expressions of individual experience and were followed by an explanation. The rules seemed unaffected by the sparse objections given. A GP's clinical experience was judged a prerequisite for applying the rules. The origin of many rules was via word-of-mouth from a colleague. The GPs acknowledged the benefits of using the rules, thereby simplifying work.
Conclusion: GPs recognize the use of rules of thumb as an immediate and semiconscious kind of knowledge that could be called tacit knowledge. Using rules of thumb might explain why practice remains unchanged although educational activities result in more elaborate knowledge.