# Rules of Thumb: Helpful, but Systematically Error Producing

The world throws a lot of complex problems at us. Even simple and mundane tasks and decisions hold a lot of complexity behind them. Deciding what time to wake up at, the best way to go to the grocery store and post office in a single trip, and how much is appropriate to pay for a loaf of bread have incredibly complex mechanisms behind them. In figuring out when to wake up we have to consider how many hours of sleep we need, what activities we need to do in the morning, and how much time it will take for each of those activities to still provide us a cushion of time in case something runs long. In making a shopping trip we are confronted with p=np, one of the most vexing mathematical problems that exists. And the price of bread was once the object of focus for teams of Soviet economists who could not pinpoint the right price for a loaf of bread that would create the right supply to match the population’s demand.
The brain handles all of these problems with relatively simple heuristics and rules of thumb, simplifying decisions so that we don’t waste the whole night doing math problems for the perfect time to set an alarm, don’t miss the entire day trying to calculate the best route to run all our errands, and don’t waste tons of brain power trying to set bread prices. We set a standard alarm time and make small adjustments knowing that we ought to leave the house ready for work by a certain time to make sure we reduce the risk of being late. We stick to main roads and travel similar routes to get where we need to go, eliminating the thousands of right or left turn alternatives we could chose from. We rely on open markets to determine the price of bread without setting a universal standard.
Rules of thumb are necessary in a complex world, but that doesn’t mean they are not without their own downfalls. As Quassim Cassam writes in Vices of the Mind, echoing Daniel Kahneman from Thinking Fast and Slow, “We are hard-wired to use simple rules of thumb (‘heuristics’) to make judgements based on incomplete or ambiguous information, and while these rules of thumb are generally quite useful, they sometimes lead to systematic errors.” Useful, but inadequate, rules of thumb can create predictable and reliable errors or mistakes. Our thinking can be distracted with meaningless information, we can miss important factors, and we can fail to be open to improvements or alternatives that would make our decision-making better.
What is important to recognize is that systematic and predictable errors from rules of thumb can be corrected. If we know where errors and mistakes are systematically likely to arise, then we can take steps to mitigate and reduce those errors. We can be confident with rules of thumb and heuristics that simplify decisions in positive ways while being skeptical of rules of thumb that we know are likely to produce errors, biases, and inaccurate judgements and assumptions. Companies, governments, and markets do this all the time, though not always in a step by step process (sometimes there is one step forward and two steps backward) leading to progress over time. Embracing the usefulness of rules of thumb while acknowledging their shortcomings is a powerful way to improve decision-making while avoiding the cognitive downfall of heuristics.

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