Why logging your coffee makes you a better drinker

A coffee log records each cup you drink: the café, the drink and a score. Without one, your sense of a café rests on memory, and memory summarizes experiences in a lopsided way.

Memory keeps the peak and the ending

In a 1993 study in Psychological Science, Daniel Kahneman and colleagues had 32 men hold a hand in 14°C water for 60 seconds. In a second trial they held it there for the same 60 seconds plus 30 more while the water warmed to about 15°C. Asked which trial to repeat, 22 of the 32 picked the longer one, even though it contained more total discomfort. The researchers concluded that people judge an experience by its worst moment and how it ends, and give little weight to how long it lasted.

Your memory of a café works on the same summary. One great cortado or one burnt latte, plus whatever happened on your last visit, can outweigh twenty ordinary cups. A score written down after each cup keeps the twenty ordinary ones in the record.

Writing it down changes behavior

A 2016 meta-analysis in Psychological Bulletin pooled 138 studies with 19,951 participants, most of them working on health goals like diet and blood pressure. People prompted to monitor their progress were more likely to reach their goals, and the effect grew when they recorded progress on paper or reported it publicly.

A Kaiser Permanente trial of about 1,700 adults found that participants who kept daily food records lost twice as much weight as those who kept none.

Neither study looked at coffee, so read them as evidence that tracking changes behavior in general, not as proof about lattes. A coffee log applies the same habit to a smaller decision: which café to walk to tomorrow.

What to record

Start with four fields: the café, the drink, the date and a score from 1 to 10. A score per drink lets you compare a café's cortado with another café's cortado instead of comparing a whole visit with a whole visit.

Add flavor notes and roast level once you want to see why you liked something. Brew method, drink size and caffeine are worth a tag too, since they explain a lot of the difference between two cups. If you brew at home, record the dose, grind setting and brew time, since those are the variables you control.

Log the average cups too

Online reviews pile up at the extremes. In a 2009 analysis in Communications of the ACM, Nan Hu, Paul Pavlou and Jie Zhang found that 78% of Amazon book ratings were four stars or higher, because people with middling opinions tend not to post. A log that only holds your 9s and 3s repeats that skew. The 6s show you what a normal day at a café looks like.

Score the cup while you drink it or right after. Given the peak-end finding, a score written that evening is more likely to lean toward how the visit ended.

How long until it sticks

In Phillippa Lally's 2010 study at University College London, 82 people repeated a chosen daily behavior for 84 days. Reaching automaticity took 66 days on average, with individual times from 18 days to a projected 254. Missing one day had little effect on the habit. Missing many lowered how automatic it became.

A month of daily logging gives you about 30 entries, enough to compare a few cafés on the drink you order most.