When Our Feelings Think for Us: The Quiet Power of the Affect Heuristic in Diagnosis
Most doctors like to believe that our decisions are built on evidence, logic, training, and experience. We know that emotion plays a role in patient care—compassion, empathy, moral distress, the weight of responsibility—but very few of us like to imagine that emotion also shapes diagnosis. The idea can feel vaguely insulting, as though acknowledging it means we’ve somehow failed at the professionalism we’ve spent decades cultivating. But the evidence is increasingly clear: our emotional reactions to patients subtly influence the way we interpret symptoms, assign risk, and select investigations, often without us realising it is happening at all.
This phenomenon is known as the affect heuristic, a cognitive shortcut in which positive or negative feelings guide decision-making. Although well described in cognitive psychology for decades[1], its role in clinical reasoning has only recently been examined in depth. The research shows something quietly uncomfortable: the emotional tone of an encounter is not just background noise. It is part of the diagnostic environment. It shapes the questions we ask, the weight we assign to findings, and even how urgently we act.
Most clinicians can think of a time when a patient’s behaviour made the assessment harder. Perhaps it was the intoxicated young man in the ED who rolled his eyes at every question. Or the anxious woman who apologised repeatedly, making you feel protective and eager to reassure her. Or the older gentleman who reminded you of someone you cared about, prompting an instinctive desire to minimise the possibility of bad news. These feelings, however fleeting, don’t stay neatly in the realm of emotion. They seep into cognition. Studies show that negative emotional states increase diagnostic error by narrowing our focus and increasing the likelihood of premature closure[2,3], while positive emotional reactions can reduce vigilance and risk perception[4].
The most insidious feature of the affect heuristic is how rational it feels in real time. When we are irritated, tired, or overwhelmed, it feels entirely reasonable to believe the patient with vague abdominal pain is simply presenting again with “their usual.” When we encounter a patient who is excessively grateful, well spoken, or easy to like, it feels equally reasonable to downplay the risk of something serious. Emotion rarely announces itself. Instead, it masquerades as judgment.
In busy clinical settings—especially emergency medicine, acute care, and primary care—the affect heuristic can be amplified by context. Fatigue, overcrowding, conflicting priorities, a chaotic ward round, a difficult conversation with a family, even stress carried in from home can prime us to interpret behaviours differently. A patient who appears demanding on a quiet day may feel unbearable on a busy one; a patient who seems stoic may be interpreted as “low risk” because that interpretation feels emotionally easier. These shifts are subtle, human, and entirely predictable.
Perhaps the most compelling work on this topic comes from studies of diagnostic reasoning under induced emotional conditions. When clinicians are placed in high negative affect states—frustration, anxiety, anger—their diagnostic accuracy declines, and they show more reliance on intuitive reasoning pathways[2]. Conversely, positive affect increases the likelihood of overlooking contradictory information[4]. Recent reviews argue that emotion is not an external contaminant of clinical reasoning but a component of it, influencing attention, perception, and risk evaluation in ways we rarely acknowledge[3,5].
Yet acknowledging this does not make us weak, unprofessional, or unthinking. It makes us reflective. It makes us safer.
One of the most powerful steps a clinician can take is simply to notice the emotional temperature of an interaction. A brief moment of self-awareness—“I’m frustrated,” “I’m rushing,” “I want this to be simple,” “I really like this patient”—can interrupt the drift toward biased cognition. Naming emotion reduces its unconscious impact, a finding consistent across behavioural science and physician performance research[3]. It also allows us to ask the most important question in any bias-prone moment: What else could this be?
There is another gift in recognising the affect heuristic: it returns humanity to the diagnostic encounter. Emotion is not the enemy of clinical reasoning. It is the backdrop against which reasoning takes place. Our reactions often reflect not just the patient but the situation—our workload, our wellbeing, our fatigue, our experiences, and yes, our biases. By paying attention to this internal landscape, we create space for better decisions and better care.
And perhaps most importantly, we extend ourselves the same compassion we often strive to give our patients. We acknowledge that we work in emotionally complex environments where perfection is impossible, uncertainty is constant, and our feelings—whether frustration, warmth, discomfort, or fear—are simply part of being human.
Recognising the affect heuristic does not diminish our professionalism.
It deepens it.
References
Finucane ML, Alhakami A, Slovic P, Johnson SM. The Affect Heuristic in Judgments of Risks and Benefits. Journal of Behavioral Decision Making. 2000. Available at: https://stanford.edu/~knutson/jdm/finucane00.pdf
Westbrook JI, Braithwaite J, et al. Affective influences on clinical reasoning and diagnosis. 2022. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9424059/
Djulbegovic B, Hozo I. Heuristic decision-making in medicine. 2012. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC3341653/
Isen AM, Rosenzweig AS, Young MJ. The influence of positive affect on clinical problem solving. Medical Decision Making. 1991.
Lerner JS, Li Y, Valdesolo P, Kassam KS. Emotion and Decision Making. Annual Review of Psychology. 2015.