The tail of the past
Lesson 16 of 31 in the course “Brain Hacks”. Free, with animations and a quiz.
The past doesn’t let go right away
You argue with a friend, and ten minutes later you snap at your mum in a chat. You look at expensive trainers, and ordinary ones suddenly seem cheap. You approve three applications in a row, and on the fourth you feel like saying no. Every moment leaves a tail: a mood, a comparison, an expectation. And that tail quietly slips into the next decision, even though it has nothing to do with it. This is priming too, not by words but by previous experience. This lesson covers where the effect is confirmed across millions of real decisions, where it turned out to be greatly exaggerated, and how to stop the past from deciding for you.
The three-bowl experiment
You can test this at home. Set out three bowls: cold water, hot (not scalding) and room temperature. Hold your left hand in the cold, your right in the hot, for a minute. Now put both into the room-temperature bowl. To the left hand the water feels hot; to the right, cold. Same water, opposite sensations. The brain doesn’t judge the thing itself, but the difference from what came just before. This is called the contrast effect, and it works not only with temperature but with prices, looks and grading. Label: solid. The problem is that “what came just before” is often not chosen by you.
Who picks what you see first
Sellers know about contrast. An estate agent first shows a couple of bad flats, and the third, average one seems like a find. A shop puts a $300 model next to $150 headphones, and Danya thinks “fine, I’ll take it”, though he walked in with an $80 budget. An online checkout first offers pricey delivery, then a “good deal”. It’s a relative of the anchor from the previous level: the first option sets the reference point. The trick isn’t necessarily a scam, but it helps to know that the feeling of “cheap” or “good” is a comparison with what you were shown before, not a property of the item. Set your own reference point: a budget and requirements before you go shopping.
After a “yes”, “no” comes easier
A big 2016 study looked at millions of real decisions by professionals: US asylum judges, loan officers in India, and baseball umpires deciding whether a pitch was a strike. The picture is the same: after an approval, the next case is a bit more likely to be rejected, even if it’s no worse. For example, asylum judges denied more often after a grant, by 0.5–3.3 percentage points, and most of all after two grants in a row. It’s the same error as in the lesson on streaks: the brain feels that “yes” can’t keep coming too long. Label: solid. The effect is small, but for the person in the queue it’s real.
Is it better to go last?
In contests where participants perform in turn and the jury scores right after each, a pattern was noticed: later performances tend to score a bit higher. It showed up in data from song contests and figure skating. One explanation: judges play it safe at the start, “saving” top scores, and by the end they compare with what they’ve seen and grow bolder. But there are other reasons too: the order isn’t always random, and strong acts are sometimes placed last on purpose. Hence the “disputed” label. The practical takeaway for study and work: if you can choose, presenting a project or taking an oral exam closer to the end is often no worse than going first.
Does sunshine make life better?
In 1983 a small phone survey found that on sunny days people rate their life as a whole higher than on rainy days. A lovely conclusion: the mood of the moment replaces the judgement of a whole life. It was retold for decades. But in 2013 researchers checked it using data from nearly a million Americans. The effect of weather on life ratings was almost zero. Label for the strong version: failed to replicate. Still, the idea that your current mood slightly colours answers about your life isn’t crazy: you saw it in the lesson on dating and happiness. The effect is just much smaller than claimed. A good lesson in how a small sample breeds big legends.
Hack: reset between decisions
Since the past slips into the next decision, put partitions between them. First: write down your criteria before you look at the options. Then you set the reference point, not the first product you’re shown. Second: score each option separately against the criteria, then go through them again in a different order. If a score changed noticeably, the order was affecting it. Third: after a fight, bad news or the euphoria of a win, take a pause, at least a walk. Fourth: make important decisions with a fresh head, not at the end of a long day when you’re drawn to the easiest option. This doesn’t turn you into a robot; it gives the decision back to you.
Try it: a choice table
Danya was looking for a room to rent. Before, he would have picked whichever he liked at the last viewing: the landlady was nice, and just before it he’d seen an awful place. This time he wrote down three criteria in advance: price, commute to uni, quiet. After each viewing he gave scores from 1 to 5, without comparing to the previous one. At the end he added them up: option B won with 11, even though C had been the “wow” at the viewing. Try this for any choice: a course, a subscription, a laptop, an internship. Write 3–4 criteria before you look at options, score them one at a time, then add up. You’ll be surprised how often the “wow” option loses to the table.
Check yourself
- Hands were in cold and hot water, then both went into room-temperature water. What does this show?
Correct answer: The brain judges the difference from what came just before. Yes. It’s the contrast effect: the same water feels hot or cold depending on what came before. - Asylum judges denied the next case slightly more often after an approval. What error does this resemble?
Correct answer: The feeling that “yes” can’t keep coming too long. Yes. It’s the same trap as with coin flips: after a run of “yes”, a “no” feels due, though cases are independent. - A small survey: on sunny days people rate their lives higher. What did data from nearly a million people show?
Correct answer: The effect of weather is almost zero. Yes. Big data found almost no effect. A small sample produced a big legend. - Danya is choosing a laptop out of five. How can he protect himself from the “tail” of earlier viewings?
Correct answer: Write criteria in advance and score each separately. Yes. Criteria set before viewing fix your own reference point, and separate scores remove the effect of order.