Cognitive Biases
Biases in Decision Making
Explore how cognitive biases systematically warp financial judgments, consumer choices, and risk assessments. Through scenarios drawn from investing, medicine, shopping, and organizational life, you will learn to detect the invisible forces that push decisions away from rationality and practice concrete techniques for resisting them.
Context
Why this exercise
Most consequential decisions in modern life — what to buy, when to sell, which surgery to consent to, whether to keep going on a failing venture — are made under the same set of cognitive distortions that Kahneman and Tversky spent forty years cataloguing. The biases that shape these decisions are not exotic; they are universal, predictable, and most damaging precisely when the stakes are highest. This exercise focuses on the six biases that quietly drive everyday financial, medical, and consumer decisions: sunk cost, loss aversion, framing, choice overload, the peak-end rule, and the gap between bias awareness and bias immunity.
Before you start
The intellectual foundation here is Prospect Theory, developed by Daniel Kahneman and Amos Tversky in 1979 and later expanded in Kahneman's 'Thinking, Fast and Slow.' Prospect Theory replaced the rational-actor model of classical economics with an empirically grounded account of how people actually evaluate uncertain outcomes. Three findings drive most of what you will encounter in this exercise. First, losses loom roughly twice as large as equivalent gains — a fMRI-confirmed asymmetry that distorts every decision involving potential downside. Second, people evaluate outcomes relative to a reference point rather than in absolute terms, which is why framing the same outcome as a gain or a loss flips behavior. Third, probabilities at the extremes get distorted: small probabilities are overweighted (which is why people overinsure against rare events) and near-certainties get treated as certainties (which is why the move from 99% to 100% feels disproportionately important).
Several other mechanisms layer on top of Prospect Theory. The sunk cost fallacy hijacks loss aversion by making abandonment feel like loss realization, so people throw good money after bad to avoid the psychological pain of accepting that earlier money is gone. Choice overload, demonstrated in Sheena Iyengar's famous jam experiment, degrades decision quality when options exceed working-memory capacity — more choices feel like freedom but produce lower satisfaction and higher rates of decision deferral. The peak-end rule, identified by Kahneman through colonoscopy and cold-water studies, shows that retrospective evaluation of an experience is dominated by its emotional peak and its ending while duration is largely neglected. And critically, awareness of these biases provides almost no protection against them — meta-analyses show knowledge-based debiasing produces only ~6% improvement, while structural interventions (pre-mortems, checklists, red teams) produce 25-40% gains.
As you work the scenarios, practice the diagnostic move of asking what reference point is driving the felt value of the option. Where does the gain or loss frame come from? What would a clean-slate test reveal — would you choose to enter this situation today knowing what you now know? Notice that the wrong-answer options frequently misdiagnose the bias by naming the wrong mechanism, and the explanations are designed to discriminate between adjacent biases that look similar but have different countermeasures. For deeper treatment, see Decision Making on structured choice frameworks and Cognitive Biases: Decision & Social for the full taxonomy of decision-relevant biases.