Algorithms to Live By maps computer science to daily dilemmas

1

Look then leap

Reject roughly the first 37 percent of options purely as a benchmark, then commit to the next one that beats everything seen so far.

Christian and Griffiths open with the secretary problem: you must hire the best candidate from a fixed pool, deciding immediately after each interview with no going back. The math says interview and reject the first roughly 37 percent only to learn the quality bar, then hire the very next candidate who tops that group. That look-then-leap rule yields a 37 percent chance of the actual best—better than any rival strategy—even though it still fails most of the time.

They extend the pattern to apartments, dating, and parking. If you can roughly estimate how many options you will see, spend the first third of the window purely gathering information. After that threshold, take the first option that outperforms everything already observed.

The model needs a known pool size, random order, and no callbacks. Real searches rarely meet those conditions. Its lasting gift is the mental model: endless searching costs the option you already passed, stopping too early has a cost too, and the 37 percent rule anchors the vague feeling that it might be time to decide.

In practice: In a three-month apartment hunt, spend the first month only viewing places, then take the next one better than all of those early options.

2

Horizon sets the mix

Whether to try something new or stick with a known favorite should rise and fall with how much time remains to use what you learn.

The multi-armed bandit problem casts a gambler facing several slot machines with unknown payouts who must choose, each pull, whether to keep playing a machine that has paid or try one that might be better. Christian and Griffiths find the same tension in restaurants, careers, and partners.

The optimal solution, the Gittins index, gives each option one number balancing known average payoff against the value of new information. Trying something untried scores higher when a long horizon remains to exploit the discovery. The math validates a comforting pattern: a young person sampling widely is not reckless, and an older person returning to favorites is not merely set in their ways.

Simpler heuristics approximate the heavy index. Upper Confidence Bound methods used in A/B testing favor high-uncertainty options because uncertainty itself carries upside. A choice is never only about immediate expected payoff; runway left changes what the right move even is.

In practice: A newcomer to a city should keep trying unfamiliar restaurants; someone with only a short stay left should default to the known favorite.

3

Sort only what you search

Full organization pays only when you search often enough to recoup the cost; comparison sorting cannot beat roughly n log n operations.

Computer scientists have hard limits: comparison-based sorting cannot beat roughly n log n operations for n items, while a method like bubble sort runs on the order of n-squared and becomes impossible as collections grow. Christian and Griffiths reframe alphabetizing shelves, filing papers, and clearing closets through that limit.

The sorting-versus-searching tradeoff decides whether the effort is worth it. A library searched constantly justifies rigorous cataloging. A personal shelf searched twice a year probably does not; time spent alphabetizing could go elsewhere.

Arrival order also matters. Partly ordered data sorts far faster than random data, which is why real-world algorithms like Timsort detect and exploit existing order. Leaving mail, receipts, or email in loose piles and relying on selective retrieval is often smarter than imposing a full system on everything that arrives. Organization level should follow actual use, not virtue.

In practice: A busy office library warrants a full catalog; a home bookshelf touched a few times a year can stay loose without real loss.

4

Evict by recency

What you keep close should follow how recently you used it, not attachment or fear you might need it someday.

Computers manage fast small memory versus slow large storage with a cache of items likely to be needed soon. The dominant rule for what to drop when space fills is Least Recently Used: discard whatever has gone longest untouched, on the theory that recent use predicts near-future use.

Christian and Griffiths cite cognitive scientist Steve Whittaker’s work on messy desks. So-called disorganized stacking often functions as an efficient LRU cache: recent papers rise, untouched ones sink, and the pile self-organizes by recency without conscious filing. Clutter can be functional rather than lazy.

The same logic reaches closets, kitchens, and memory. Keeping an item because you might need it someday ignores the real cost of space and attention—the mistake LRU avoids. Caching works when future use resembles recent use, but fails for rare-yet-predictable items such as annual tax documents. Naming the pattern lets you purge, deliberately, whatever has sat untouched longest.

In practice: Whittaker’s desk studies found stacked papers already surface recent work and bury the untouched, mimicking a cache without a formal system.

5

Order by an explicit rule

Sequence work by shortest processing time or earliest due date rather than by whatever feels most urgent or dreaded.

Scheduling theory offers provable rules tied to the goal. To minimize total waiting time, do the shortest task first—Shortest Processing Time clears the most items fastest. To minimize the worst lateness, Earliest Due Date is optimal. When some deadlines are unreachable and the aim is fewer misses overall, the Moore-Hodgson algorithm drops the single hardest task to save the rest.

Christian and Griffiths highlight switching cost. Machines thrash when so much effort goes into choosing the next task that little time remains to run any of them. Constant hopping among email, messages, and deep work produces the same waste: overhead can eat more of the day than the tasks. Batching similar work and cutting interruptions is a grounded fix, not a fad.

The pure rules assume known lengths and deadlines and underplay the cost of stopping midway. Still, they beat anxiety-sorting, which can be provably worse than ordering by due date or length.

In practice: A mixed day of messages and deep work improves when similar tasks are batched and the list follows due date rather than dread.

6

Match prior to process

Forecasts of remaining length or size must follow whether the underlying pattern is power-law, normal, or exponential.

Bayes’s rule combines prior knowledge with new evidence, and prior shape matters enormously. Christian and Griffiths illustrate with astrophysicist J. Richard Gott’s Copernican-style reasoning on the Berlin Wall: assume you are seeing it at a random point in its life. That method fits power-law phenomena with no natural typical size—movie runs, technology lifespans, Broadway shows.

For normal distributions clustered around a mean, such as human lifespan, use the average and add a fixed remainder. Knowing someone is 40 points you toward the actuarial rest of a normal life, not a random fraction of an unknown total. Exponential cases teach a third lesson: elapsed time tells you nothing. A light bulb still burning is no more or less likely to last another hour just because it already has.

Good prediction is not one formula. It is choosing the correct family of prior from real knowledge of the process, then updating with evidence. Blind extrapolation without that pattern yields systematically bad guesses.

In practice: Gott treated the Berlin Wall as a random point in a power-law span; human age instead calls for a normal-distribution remainder around the known average.

7

Stop before the noise

Extra factors, precision, or effort can worsen the outcome; deliberate simplicity and early stopping often beat full optimization.

In machine learning, a model that fits training data too tightly captures noise as signal and then fails on new cases. Standard defenses are cross-validation against unseen data and regularization that penalizes complexity. Christian and Griffiths see the same failure in ordinary decisions.

A hiring process with twenty weighted criteria can lose to one with three, because the extras mostly encode noise from a small sample of past hires. A hedge-filled recommendation letter can help less than a short confident one; excess detail without confidence looks like fitting to irrelevancies. Athletic recruiting and stock strategies backtested on history often shine on past data and flop forward.

Early stopping—deliberately not optimizing all the way—is often superior. A network trained to full convergence typically generalizes worse than one halted partway. Past a point, more research mostly adds noise dressed as insight. Choosing to stop analyzing is a skill, not a failure of thoroughness.

In practice: A three-criterion hiring score can beat a twenty-factor rubric that mostly fits quirks from a handful of earlier hires.

8

Relax then adapt

When exact solution is intractable, drop a real constraint, solve the easier version, then bend that answer back to reality.

Large instances of problems like the traveling salesman route are computationally hopeless to solve exactly. Computer scientists relax them: strip a constraint that makes the problem hard, solve the easier version, and use the result as a bound or starting guide. Lagrangian relaxation turns a hard constraint into a penalty, producing an approximation never worse than a known bound on the true optimum.

Christian and Griffiths apply the move to decisions hemmed by budget, time, or convention. First solve as if the binding constraint did not exist. See the ideal. Only then adapt it to the real limit. Reasoning under every constraint at once is often what creates paralysis.

An everyday case is the apology. The relaxed form of a long justified excuse is simply “I’m sorry I’m late,” dropping the demand to narrate every link. That shorter version is often more useful to the listener. Intractable exactness is frequently the wrong standard; a good approximate answer reached quickly beats a perfect one reached too late or never.

In practice: Instead of a full defensive story for lateness, the relaxed move is a plain apology that drops the need to justify every detail.

9

Randomness and redesign

Limited randomness escapes local dead ends, and redesigning incentives beats trying to out-recurse other people’s strategies.

Some landscapes are full of traps. Randomized methods such as simulated annealing occasionally accept a worse move on purpose, with that willingness falling over time, the way metal cools into a strong rather than brittle structure. Christian and Griffiths treat small randomness in ordinary choices—random tie-breaks, trying an option you would otherwise skip—as a documented escape from ruts, not a cop-out.

Game theory adds another hardness. Modeling what others will do, including their model of you, spirals into infinite recursion that is provably intractable; complexity results on Nash equilibria make the point precise. Strong players and mechanism designers do not out-recurse opponents. They shape the situation so good behavior is the easy dominant choice no matter what others do.

The Vickrey second-price auction is classic: bidding your true value is always optimal regardless of other bidders. Braess’s paradox shows the societal version—adding a road can slow everyone’s commute as self-interested drivers reroute in ways that hurt the whole. The fix is better incentives, not harder individual reasoning.

In practice: In a Vickrey auction, bidding your true value is dominant no matter what others bid, removing the need to model them.