Cognitive biases
Primacy and recency effects: why we remember the start and end of a list
Sonya is in a store with a full basket. Her mom calls: “Since you’re there, pick up some more…” and quickly rattles off twelve items. There is nowhere to write them down, and her hands are full. Sonya hangs up and confidently grabs the milk and bread her mom started with, and the cookies and eggs she finished with. And what was in the middle? Something about tea, it seems. Or was it rice?
These are the primacy and recency effects, together known as the serial-position effect. From a list, the first and last items are remembered best, and the middle gets lost. The first is called the primacy effect, the second the recency effect. This is not a thinking error but an ordinary property of memory. But it gets in the way when the most important thing ends up in the middle.
Below, we look at what studies have shown, why this happens, and where it matters: in job interviews, in talks, in long to-do lists. In the middle of the article you will get the same call from Mom as Sonya did and test your memory.
Contents
In short: how the primacy and recency effects work
What they are
Imagine someone reads you a list of words and then asks you to name all you remember, in any order. If you mark which words people recalled and lay them out by their places in the list, you get a curve shaped like the letter U. High on the left: the first words are remembered well. High on the right too: the last words are remembered well. And in the middle, a dip.
This curve was described in detail by the psychologist Bennet Murdock in a 1962 paper. According to his data, the advantage of the start covers the first three or four words. The advantage of the end is wider, covering several of the last words. And everything between them is recalled about equally poorly.
It is important that the start and the end have different causes. You can see this from a simple experiment. If right after the list you are distracted for a bit, for example by subtracting threes in your head, the advantage of the end weakens noticeably, while the advantage of the start remains. This was shown back in a classic 1966 experiment. It seems the last words stay in memory only briefly, while the first ones have time to settle more firmly.
How far this can be trusted. This U-shaped curve has been found in experiments with lists for more than half a century. The disagreement is not about whether it exists but about why it looks the way it does: more on that below. There is also a caveat. The curve is visible when you have to recall on your own. When you only need to recognize words among others, it can be different. In an experiment with photographs of snowflakes, right after the showing people recognized the last pictures better, while the first ones were no better than guessing. With time the picture changed: the start was recognized better, and the end lost its advantage.
Try it yourself: Sonya’s list
Now you are in Sonya’s place. The game takes a couple of minutes. Here is what will happen.
Step 1. Mom “dictates” twelve items. The words appear on the screen one at a time and replace each other on their own. The order of the words is different for each player: it is chosen by chance.
Step 2. Name aloud or to yourself all the words you remember, in any order. You can count on your fingers. Nothing needs to be typed.
Step 3. You will see 24 words: twelve from the list and twelve new ones. Mark the ones you have just named.
Why not simply “find the familiar words”? Recognizing a word in a grid is much easier than recalling it yourself. And the U-shaped curve is best seen exactly when you recall on your own. So mark honestly: only what you managed to name before the grid.
What usually happens. If you add up the answers of many people, you get that very letter U: words from the first and last places are named more often than from the middle.
What the game can and can’t show. One list of twelve words is very little. Your curve may come out uneven, with no letter U at all, and that does not mean the effect doesn’t work on you. One extra word changes the picture a lot. That is why the game lets you go through a second list: two attempts are added together, and the curve becomes a bit more reliable. Besides, you read this article and may have tried on purpose to remember the middle. That is also an honest result.
Why the middle gets lost
Imagine you are catching balls that fly one after another. The first ones you catch calmly and have time to put in a bag. The last ones you are still holding in your hands. And the middle ones arrive when your hands are busy, and some fall. This is an image, not the exact workings of memory, but it conveys the main point.
The start gets repeated. While the list has only just begun, we say the first words over to ourselves, and more than once. Then there are more words, and each one gets less time for repeating. This is one of the common explanations of the primacy effect. We are not relying on a specific experiment here, so take it as a plausible explanation, not a proven fact.
The end still “rings” in the head. The last words sounded just now, and you can simply “read them off” from memory while you haven’t been distracted. That is why the advantage of the end weakens after a short pause with counting. Scientists still argue about whether there is a separate short-term memory for this or whether memory in general works this way. A 2005 review goes through the arguments of both sides. For everyday life the answer matters less: the middle gets lost either way.
Where it matters
Interviews and evaluations. Order affects not only what we remember but also how we evaluate. In one study, students who had been taught to evaluate candidates watched one person do two work tasks. He did one well and the other badly, and the order was varied. The task that came second had the stronger influence on the final rating. This is a related effect, not quite the same as with a list of words. But the lesson is shared: the last impression weighs more than it seems.
Competitions. In a study of the Eurovision Song Contest and figure skating competitions, scores rose with the performance number: those who performed later received higher scores on average. And this was so even when the judges gave their scores right after each performance.
Talks and meetings. From a long talk people usually take away the introduction and the last slide. If the main argument came at the twentieth minute, it may not be remembered. This is an everyday observation, but it follows directly from the curve.
To-do lists and the news. From a long to-do list, the middle items drop out most easily. It seems the same happens with a news broadcast: the first and last stories are easier to recall. This is an observation, not the result of a separate experiment. How the end affects the memory of a whole event is covered in a separate article: the peak-end rule.
How not to lose the middle
The primacy and recency effects are among the entries on the cognitive bias map, in the section on memory. Next to them is the misinformation effect: how what we hear after an event changes our memory of it.
Frequently asked questions
Is this the same as a “first impression”?
Similar, but not the same. Here we are talking about memory: which items of a list will be recalled. A first impression of a person is about how the first information colors everything else. The word “primacy” is used in both cases, so they are easy to confuse.
Which is stronger, the start or the end?
It depends on when you recall. Right after the list, the end is usually remembered well. If time has passed or you were distracted, the advantage of the end disappears, and the start remains.
Do the effects look the same if you only have to recognize things?
Not necessarily. The U-shaped curve is clearest when you recall on your own. When things only need to be recognized, it can be different: in the experiment with snowflake photographs, right after the showing the last pictures were recognized better, while the first ones were no better than guessing. With time the start was recognized better, and the end lost its advantage.
