Neglect of Probability: A Hidden Risk in Decision Making

1 minutes reading time
Published 4 Dec 2023
Reviewed by: Kasper Karlsson
Updated 7 Feb 2024

The concept of "probability" should take center stage in our decision-making processes. However, there's a pervasive tendency to overlook this critical aspect, leading to what experts refer to as the "neglect of probability." This cognitive bias can have far-reaching consequences, particularly in sectors like finance, where the stakes are high and the margins for error are slim.

Understanding Probability Neglect

At its core, neglect of probability is a cognitive bias that occurs when people disregard the likelihood of events happening, especially in situations involving risk and uncertainty. Instead of evaluating the true chances and potential outcomes, decisions are often based on anecdotal evidence or emotional responses. This negligence can stem from a lack of understanding, an inherent difficulty in processing statistical information, or simply the human tendency to focus on outcomes rather than likelihoods.

Probability Neglect in Finance

To illustrate, consider an example of probability neglect in finance. Investors might become charmed by a particular stock after hearing success stories of massive returns. Blinded by the potential outcome, they may ignore the actual probability of such success. A startup, for instance, may have a high potential for growth, but also a high chance of failure—something an investor might overlook when caught up in the excitement of possible high returns. This is something that famous investors such as Aswath Damodaran, known as the Dean of Valuation, assesses through his "Probabilistic Margin of Safety" framework.

Cognitive Biases and Heuristics

Why do we fall into this trap? It's partly because of cognitive biases and heuristics. These mental shortcuts allow us to make quick decisions without analyzing every possible outcome, but they can also lead us astray. For example, the availability heuristic makes us overestimate the likelihood of events that are easily recalled (like plane crashes after high-profile media coverage) while underestimating the probability of less sensational but more common events (such as car accidents).

Combating Probability Neglect

How do we combat this neglect? Education and awareness are the first steps. By understanding the common pitfalls in our thinking, we can start to question our intuitive judgments and consider probability more carefully. In finance, this might mean looking beyond the potential gains and thoroughly evaluating the risk-reward ratio.

Moreover, employing decision-making frameworks and tools that quantify probabilities can help. Techniques such as decision trees, risk assessments, and statistical models can force a more nuanced consideration of probabilities.

Probability in Everyday Life

It's not just in finance where neglect of probability can have a significant impact. Everyday decisions, like choosing to skip a flu shot because you've never gotten the flu, can be influenced by this bias. The actual probability of catching the flu in any given year may be low, but over a lifetime, the chances add up—and the decision to vaccinate or not should hinge on this cumulative risk.

Final Thoughts

In a nutshell, neglect of probability is a common yet frequently overlooked bias that undermines rational decision-making. It has particularly insidious effects in finance, where it can lead to a gross misjudgment of risk and reward. By becoming more probability-literate and applying more rigorous analytical tools, we can safeguard ourselves against this bias and make better-informed decisions. After all, probability may not always play in our favor, but acknowledging and understanding it will always be a winning strategy.


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