In 1962, psychologist Bennet Murdock read lists of words to 103 participants and asked them to recall as many as they could.
The results drew a U-shaped curve that has been replicated for 140 years: people remember the first few items and the last few items. Everything in the middle? Forgotten.
This is the serial position effect — and it has profound implications for how you design email sequences, trial onboarding, and any content delivered in a series.
The Science: What Happens to Information in a Sequence
Murdock (1962, Journal of Experimental Psychology, N = 103) tested lists of 10 to 40 words at different speeds. The pattern was remarkably consistent:
- First 3-4 items recalled best (primacy effect)
- Last ~8 items recalled well (recency effect)
- Everything in the middle recalled poorly — a flat line of forgetting
The curve held across list lengths and presentation rates. It's one of the most robust findings in all of psychology.
Why the First Items Win: Primacy
When you hear the first item in a sequence, your working memory is empty. You have full processing capacity. You rehearse it. You encode it deeply. It gets transferred to long-term memory.
By the time the fourth or fifth item arrives, your working memory is juggling multiple items. New information competes with old. Encoding gets shallower. Items start falling through the cracks.
Asch (1946) demonstrated this powerfully in social perception: describing someone as "fun, witty, and vicious" produces a significantly more favorable impression than "vicious, witty, and fun." Same traits, reversed order, different judgment. The first trait creates a schema through which all subsequent traits are interpreted.
Sullivan (2019, Social Psychological and Personality Science) conducted a single-paper meta-analysis confirming the primacy effect in impression formation is reliable and replicable.
Why the Last Items Win: Recency
The last few items in a sequence benefit from still being in short-term memory when recall is tested. They haven't been displaced yet.
But here's the critical caveat: Glanzer & Cunitz (1966) showed that a 30-second distractor task completely eliminated the recency effect. Those 46 US Army participants counted backwards for 30 seconds, and the last items were forgotten just like the middle ones.
Primacy survived the delay. Recency didn't.
What this means: Your first email gets encoded in long-term memory. Your last email is only in working memory — powerful but fragile. Any distraction between receiving it and taking action erases the advantage.
Why the Middle Disappears
The middle of any sequence suffers from two directions of interference:
- Proactive interference: Earlier items compete for retrieval
- Retroactive interference: Later items overwrite middle items
The middle has no special protection. No primacy encoding advantage. No recency working-memory boost. It's the cognitive dead zone.
Online Evidence: Clicking Behavior
Murphy, Hofacker & Mizerski (2006, Journal of Computer-Mediated Communication, N ≈ 3,888) ran two field experiments on link clicking behavior using a Latin Square design (randomizing content across positions):
| Position | Click-through Rate | |----------|-------------------| | Position 1 (first) | 10.5% | | Position 2 | 9.1% | | Position 3 | 8.4% | | Position 4 | 8.0% | | Position 5 | 7.3% (lowest) | | Position 6 (last) | Uptick |
First position: most clicked. Middle positions: declining. Last position: recovery. The U-curve appears in digital behavior too.
What This Means for Your Email Sequences
Email 1 Is Your Most Important Email
Your first email creates the lens through which every subsequent email is judged. It:
- Gets the most rehearsal time (reader's attention is fresh)
- Transfers to long-term memory (survives delays and distractions)
- Establishes an identity frame that confirmation bias then protects
- Sets expectations for everything that follows
If your first email is forgettable, every email after it faces an uphill battle.
The Middle Is Where Messages Go to Die
Emails 2-4 in a typical sequence are the cognitive dead zone. They arrive when the reader is:
- Past the initial excitement (primacy faded)
- Not yet feeling urgency (recency hasn't kicked in)
- Being interfered with by both earlier and later emails
The rescue strategy: Make middle emails distinctive. The von Restorff effect (1933) shows that items that break a pattern are remembered better. In your middle emails, use pattern interrupts: unexpected formats, surprising subject lines, different content types.
The Final Email Must Be Immediate
Recency is powerful but fragile. That final trial-ending email needs to arrive as close to the decision moment as possible. A reminder sent three days before trial ends will be forgotten (Glanzer & Cunitz: 30 seconds of distraction eliminates recency). A reminder sent the morning of carries the full recency boost.
The Architecture of a 14-Day Trial
Applying serial position research to trial design:
| Days | Position | Strategy | |------|----------|----------| | Day 1 | PRIMACY | Strongest value, identity transformation, "wow" moment | | Days 2-5 | Middle (early) | Distinctive content, pattern interrupts, build investment | | Days 6-10 | Middle (deep) | Progressive commitment, social proof, skill-building | | Days 11-13 | Approaching recency | Show accumulated investment, loss framing | | Day 14 | RECENCY | Peak-end optimization, strongest CTA, urgency |
Day 1 and Day 14 carry disproportionate memory weight. Everything else is supporting structure.
The Nervous System Angle
The serial position effect maps onto attentional arousal:
- First item: Orienting response (novelty → cortisol + norepinephrine → enhanced encoding)
- Middle items: Habituation (familiarity → reduced arousal → shallow processing)
- Last item: Closing response (anticipation of end → renewed attention → working memory activation)
For burned-out founders with impaired working memory (Post #150: g = -0.36), the middle zone is even more dangerous. Their cognitive capacity is already reduced — they're relying almost entirely on primacy and recency. Your middle emails don't just compete with other emails; they compete with a compromised attention system.
What to Do With This
- Treat email #1 as your most important email. Not your introduction. Not your "welcome." Your strongest, most identity-shaping message.
- Use the von Restorff effect in the middle. Break patterns. Surprise. Be distinctive. The middle only survives if it's visually, structurally, or emotionally different from what came before.
- Time your final message to the decision point. Recency fades in 30 seconds. Don't send your "trial ending" email three days early.
- Structure each individual email the same way. First sentence = primacy (your hook). Middle paragraphs = supporting content. Last sentence = recency (your CTA).
- Accept that the middle will underperform. Don't put your most critical content in emails 3 and 4. Use them for building investment, not delivering key messages.
The serial position effect has been replicated for 140 years across hundreds of studies. Your email sequence is not exempt from how human memory works.
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Sources:
- [Murdock (1962). "The serial position effect of free recall." Journal of Experimental Psychology, 64(5), 482-488.](https://psycnet.apa.org/record/1963-06156-001)
- [Glanzer & Cunitz (1966). "Two storage mechanisms in free recall." Journal of Verbal Learning and Verbal Behavior.](https://psycnet.apa.org/record/1966-12905-001)
- [Sullivan (2019). "The Primacy Effect in Impression Formation: Some Replications and Extensions." Social Psychological and Personality Science.](https://journals.sagepub.com/doi/abs/10.1177/1948550618771003)
- [Murphy, Hofacker & Mizerski (2006). "Primacy and Recency Effects on Clicking Behavior." Journal of Computer-Mediated Communication, 11(2), 522-535.](https://academic.oup.com/jcmc/article/11/2/522/4617731)
- [Von Restorff (1933). Isolation effect — distinctive items recalled better in homogeneous lists.](https://en.wikipedia.org/wiki/VonRestorffeffect)
- Ebbinghaus (1885). Original serial position effect discovery through self-experimentation. accessibility.link.new-tab