INTRODUCTION
The clinical decision-making process in Primary Care (PC) is performed under conditions of greater uncertainty (1, 2), than in other clinical settings because in PC symptoms and signs are often poorly defined, the early stages of clinical processes predominate, and it is often not possible to identify a clear diagnostic code. In addition, there is very limited time available per patient (3), which makes the clinical decision-making process even more difficult, given the cognitive limitation involved, which may lead to a preference for the use of so-called system 1 (rapid, non-conscious) strategies over system 2 (analytical, reflective) strategies (4). As a result, general practitioners are likely to use "unconscious thought "(5) during the diagnostic process in PC, which is called by various names and assessments ("gut feelings", first impressions, intuition, heuristics), depending on the authors. However, the empirical evidence on the use of such procedures in clinical practice is very limited and, sometimes, contradictory.
Thus, Herbert Simon defined "intuition" as recognition ("the observable fact that people reach solutions to problems suddenly"); for this author, the process by which decision-makers collect and evaluate all the information, weigh its weight according to certain criteria, and combine it to maximize the chances of achieving the objectives ("optimization") is not very feasible in the real world; therefore, human beings usually choose to use simple strategies that are sufficiently adequate for the proposed ends (6). Subsequently, Kahneman and Tversky identified certain practical rules or "heuristics" that are very efficient in saving time and cognitive effort (7), which allow for greater speed in the decision-making process. Gigerenzer, for his part, defines a heuristic as a simple decision strategy that ignores part of the available information, focusing only on some relevant predictors (6). Finally, Wooley and Kostopoulou consider that the concept of clinical intuition goes beyond the experience of "first impressions" (8), including in it also the feeling of difficulty or discomfort (gut feeling) derived from tacit knowledge acquired through experience (what Gigerenzer calls recognition heuristic) (9), or the "aha" phenomenon, in which a problem is solved after a process of maturation or incubation (when analytical thinking has previously been unable to solve it) (10).
This type of "unconscious thinking" strategies, also identified as the in attentional deliberation effect (11), is considered by some authors to be cognitive illusions or simply irrational. Thus, in the Conceptual Framework of Heuristics and Biases proposed by Kahneman and Tversky, they have usually been considered sources of error, an approach shared by many authors who have researched clinical decision and error (12). Gigerenzer, by contrast, in his Fast and frugal heuristic framework attempts to understand when and how people's reliance on simple heuristic decisions can result in intelligent and successful goal-oriented behavior; in these cases, decision-makers rely on a repertoire of heuristics (what he calls an adaptive toolbox) in which each heuristic is tailored to a particular situation (9).
More than 100 heuristics have been described in the literature I13), with significant discrepancies regarding the benefit of their use in clinical decision-making: while some authors consider them a useful resource, (14,15,16) the majority opinion in the medical literature over the last 30 years is that these heuristics and cognitive processing are the primary cause of diagnostic error (12, 17). In the clinical setting, getting it wrong, either by over- or under-diagnosis, increases the risk of harmful effects and unnecessary costs associated with "diagnostic error", defined as error thatis incorrect, mistimed, or ignored (18).
A recent study of 100 cases of diagnostic errors found at least one cognitive error in 74% of cases (19). A quasi-systematic review of the use of heuristics in clinicians shows that representativeness, availability, and overconfidence are some of the most used heuristics in clinical practice (20). However, they do not find an answer whether the use of these heuristics produces systematic errors and advocate evaluating their use in real clinical practice conditions.
The representativeness heuristic refers to "the degree of correspondence between a sample and a population that makes us think an event is likely if it seems representative of a larger class" (21). The availability heuristic makes judgements about the likelihood or frequency of certain events based on how easy it is to recall examples of them (22). The overconfidence heuristic occurs when one overestimates one's own skills and abilities (23).
An overview review of the use of these three heuristics in clinical decision-making in PC (24), found little empirical evidence of their use in clinical practice, finding that most studies were conducted in laboratory conditions using vignettes, with reasonable doubts about their applicability in real clinical practice. This scarcity of studies in real practice is even greater in PC (where only 6 of the 49 studies were conducted). The available evidence does not allow us to know to what extent the bias derived from the use of heuristics is a relevant factor in Diagnostic Error (25).
In view of all these questions, this paper explores the use of heuristics in clinical decision-making by general practitioners in everyday clinical practice and their potential relationship with diagnostic error.
Given the lack of previous operational definitions to measure the clinical use of heuristics of representativeness, availability, and overconfidence, a previous article made an approximation to their operational definition based on the first diagnostic impression (representativeness), the identification of possible differential diagnoses (availability) and the degree of confidence in the proposed diagnosis on the part of the doctors participating in the study (overconfidence) (26). The objectives of the present study are: To analyse the possible use of the Representativeness, Availability and Overconfidence heuristics in the decision-making process of PC doctors in the case of patients presenting with new episodes of dyspnoea, and to study the possible relationship (or association) between unconscious thinking applied through this type of heuristic and diagnostic error.