The affect heuristic, as described by Daniel Kahneman in Thinking, Fast and Slow, is a mental shortcut where people make decisions based on their immediate emotional reactions (“affect”) rather than a thorough analysis of facts. Kahneman explains that this heuristic is driven by System 1 thinking—fast, intuitive, and automatic—where emotions like fear, pleasure, or disgust heavily influence judgments about risks and benefits.
For example, if something feels good or appealing (e.g., a positive image of a technology), people are more likely to perceive it as beneficial and low-risk. Conversely, if something evokes negative emotions (e.g., dread about nuclear power), they’re likely to judge it as risky and undesirable, even if evidence suggests otherwise. Kahneman notes that this can lead to biased decisions, as emotional reactions often override objective data.
The affect heuristic was first formalized by Paul Slovic and colleagues, but Kahneman integrates it into his framework to show how System 1’s reliance on feelings can distort rational decision-making, especially under uncertainty. It explains why people might overestimate risks of dramatic but rare events (like plane crashes) or underestimate familiar risks (like driving), based on how these evoke emotional responses.
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