What people actually remember from a presentation
Recall is not a flat average of what you said. It has a shape, it has been measured since 1962, and knowing the shape changes where you put your best material.
Not an even sample of what you said. Recall has a reliable shape: the opening and the close survive, and the middle largely does not. It was measured in 1962 and has held up since.
A second effect sits on top of it. When people judge an experience afterwards, they weight its most intense moment and its ending, and they almost ignore how long it lasted. So the practical question is not "how do I make all of this memorable" — it is "which two moments am I willing to spend on".
Ask someone the day after a presentation what it was about and you get one or two sentences. Not a summary — fragments. The opening image, a number that surprised them, the last thing said before the questions.
That is not because they were rude or distracted. It is what recall does, and it does it in a shape that has been measured repeatedly since the early 1960s.
The shape
In 1962 Bennet Murdock read people lists of words and asked them to recall as many as they could, in any order. Plotting the probability of recall against the position of each word in the list produces a curve that is now in every cognitive psychology textbook.
Two mechanisms produce it. Early items get more rehearsal, so they reach long-term memory — that is primacy. Late items are still sitting in immediate memory when recall starts — that is recency. Items in the middle get neither advantage.
A presentation is not a word list, and the analogy should not be pushed too far. But the underlying constraint is the same one, and anyone who has sat through a day of conference sessions has the evidence first-hand.
The second effect, which is stranger
In 1993 Kahneman and colleagues had people hold a hand in painfully cold water for sixty seconds. Then a second trial: the same sixty seconds, followed by thirty more during which the water was allowed to warm slightly — still unpleasant, just less so.
The second trial contains strictly more discomfort. It is the first one plus extra. When participants were asked which they would repeat, most chose the longer one.
Three years later the same authors examined 682 patients undergoing colonoscopies, which at the time ranged from four to sixty-nine minutes. How patients rated the experience afterwards was predicted by the worst moment and by the final moments. It was almost unrelated to how long it went on.
This is called the peak-end rule, and it has an uncomfortable implication for anyone who has ever fought for a longer slot. Twenty minutes and forty minutes leave behind roughly the same residue. What differs is whether there was a peak worth keeping.
What follows from this
Your best material is probably in the wrong place
Most decks are built in the order the work was done: context, method, analysis, findings, recommendation. That puts the one thing you want remembered at the point of lowest recall — somewhere after the middle, when attention has thinned and before the close has arrived to sharpen it.
The fix is not to speak louder there. It is to move it. If the recommendation is the payload, it belongs in the first ninety seconds and again in the last thirty, with the reasoning in between. That order feels wrong to build and it is far easier to listen to.
Decide the peak on purpose
Something will be the most vivid moment. If you do not choose it, the room chooses — and it tends to pick the moment you fumbled a question, or an ugly slide, or the point where the projector failed.
A chosen peak is usually one of three things: a number that is genuinely surprising, a concrete example with a name and a date attached, or a sentence that names something everybody in the room had noticed and nobody had said. One is enough. Two competing peaks average into no peak at all.
The last thirty seconds are worth more than the middle five minutes
And they are almost always the least rehearsed part, because preparation runs out of time in the order the document was written. If you have limited rehearsal, spend it at the ends.
One caveat worth stating. Murdock's curve comes from word lists, and the peak-end studies come from pain, not from meetings. Nobody has run the controlled equivalent on quarterly business reviews, and anybody who tells you the numbers transfer exactly is overselling. What transfers is the shape and the direction, which is enough to change how you order a deck.
A third effect, briefly
In 1933 Hedwig von Restorff showed that an item which differs from everything around it is recalled far better than its neighbours. One coloured word in a list of black ones.
This is why a single deliberate break in format works — one slide with nothing on it but a sentence, one moment where you stop and step away from the screen, one physical object put on the table. It also explains why decks where every slide is dramatic are so forgettable. If everything is isolated, nothing is.
The question this leaves you with
Not "how do I make this memorable". You cannot make twenty minutes memorable; the architecture of recall does not allow it. The question is narrower and more answerable:
Answer those two before you open the slide software, and the middle can be as ordinary as it likes. It was going to be forgotten regardless — that is not a failure of the middle, it is what the middle is for.
Sources
- Murdock, B. B. (1962). The serial position effect of free recall. Journal of Experimental Psychology, 64(5), 482–488.
- Kahneman, D., Fredrickson, B. L., Schreiber, C. A., & Redelmeier, D. A. (1993). When more pain is preferred to less: adding a better end. Psychological Science, 4(6), 401–405.
- Redelmeier, D. A., & Kahneman, D. (1996). Patients' memories of painful medical treatments. Pain, 66(1), 3–8.
- von Restorff, H. (1933). Über die Wirkung von Bereichsbildungen im Spurenfeld. Psychologische Forschung, 18, 299–342.