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I’ve tested 100s of psychological tactics on my email subscribers. In this blog, I reveal the five tactics that actually work.

You’ll learn about the email tactic that got one marketer a job at the White House.

You’ll learn how I doubled my 5 star reviews with one email, and why one strange email from Barack Obama broke all records for donations.

5 Psychological Tactics to Write Better Emails

Imagine writing an email that’s so effective it lands you a job at the White House.

Well, that’s what happened to Maya Shankar, a PhD cognitive neuroscientist. In 2014, the Department of Veterans Affairs asked her to help increase signups in their veteran benefit scheme.

Maya had a plan. She was well aware of a cognitive bias that affects us all—the endowment effect. This bias suggests that people value items higher if they own them. So, she changed the subject line in the Veterans’ enrollment email.

Previously it read:

• Veterans, you’re eligible for the benefit program. Sign up today.

She tweaked one word, changing it to:

• Veterans, you’ve earned the benefits program. Sign up today.

This tiny tweak had a big impact. The amount of veterans enrolling in the program went up by 9%. And Maya landed a job working at the White House

Inspired by these psychological tweaks to emails, I started to run my own tests.

Alongside my podcast Nudge, I’ve run 100s of email tests on my 1,000s of newsletter subscribers.

Here are the five best tactics I’ve uncovered.

1. Show readers what they’re missing.

Nobel prize winning behavioral scientists Daniel Kahneman and Amos Tversky uncovered a principle called loss aversion.

Loss aversion means that losses feel more painful than equivalent gains. In real-world terms, losing $10 feels worse than how gaining $10 feels good. And I wondered if this simple nudge could help increase the number of my podcast listeners.

For my test, I tweaked the subject line of the email announcing an episode. The control read:

“Listen to this one”

In the loss aversion variant it read:

“Don’t miss this one”

It is very subtle loss aversion. Rather than asking someone to listen, I’m saying they shouldn’t miss out. And it worked. It increased the open rate by 13.3% and the click rate by 12.5%. Plus, it was a small change that cost me nothing at all.

2. People follow the crowd.

In general, humans like to follow the masses. When picking a dish, we’ll often opt for the most popular. When choosing a movie to watch, we tend to pick the box office hit. It’s a well-known psychological bias called social proof.

I’ve always wondered if it works for emails. So, I set up an A/B experiment with two subject lines. Both promoted my show, but one contained social proof.

The control read: New Nudge: Why Brands Should Flaunt Their Flaws

The social proof variant read: New Nudge: Why Brands Should Flaunt Their Flaws (100,000 Downloads)

I hoped that by highlighting the episode’s high number of downloads, I’d encourage more people to listen. Fortunately, it worked.

The open rate went from 22% to 28% for the social proof version, and the click rate, (the number of people actually listening to the episode), doubled.

3. Praise loyal subscribers.

The consistency principle suggests that people are likely to stick to behaviours they’ve previously taken. A retired taxi driver won’t swap his car for a bike. A hairdresser won’t change to a cheap shampoo. We like to stay consistent with our past behaviors.

I decided to test this in an email.

For my test, I attempted to encourage my subscribers to leave a review for my podcast. I sent emails to 400 subscribers who had been following the show for a year.

The control read: “Could you leave a review for Nudge?”

The consistency variant read: “You’ve been following Nudge for 12 months, could you leave a review?”

My hypothesis was simple. If I remind people that they’ve consistently supported the show they’ll be more likely to leave a review.

It worked.

The open rate on the consistency version of the email was 7% higher.

But more importantly, the click rate, (the number of people who actually left a review), was almost 2x higher for the consistency version. Merely telling people they’d been a fan for a while doubled my reviews.

4. Showcase scarcity.

We prefer scarce resources. Taylor Swift gigs sell out in seconds not just because she’s popular, but because her tickets are hard to come by.

Swifties aren’t the first to experience this. Back in 1975, three researchers proved how powerful scarcity is. For the study, the researchers occupied a cafe. On alternating weeks they’d make one small change in the cafe.

On some weeks they’d ensure the cookie jar was full.

On other weeks they’d ensure the cookie jar only contained two cookies (never more or less).

In other words, sometimes the cookies looked abundantly available. Sometimes they looked like they were almost out.

This changed behaviour. Customers who saw the two cookie jar bought 43% more cookies than those who saw the full jar.

It sounds too good to be true, so I tested it for myself.

I sent an email to 260 subscribers offering free access to my Science of Marketing course for one day only.

In the control, the subject line read: “Free access to the Science of Marketing course”

For the scarcity variant it read: “Only Today: Get free access to the Science of Marketing Course | Only one enrol per person.”

130 people received the first email, 130 received the second. And the result was almost as good as the cookie finding. The scarcity version had a 15.1% higher open rate.

5. Spark curiosity.

All of the email tips I’ve shared have only been tested on my relatively small audience. So, I thought I’d end with a tip that was tested on the masses.

Back in 2012, Barack Obama and his campaign team sent hundreds of emails to raise funds for his campaign.

Of the $690 million he raised, most came from direct email appeals. But there was one email, according to ABC news, that was far more effective than the rest. And it was an odd one.

The email that drew in the most cash, had a strange subject line. It simply said “Hey.”

The actual email asked the reader to donate, sharing all the expected reasons, but the subject line was different.

It sparked curiosity, it got people wondering, is Obama saying Hey just to me?

Readers were curious and couldn't help but open the email. According to ABC it was “the most effective pitch of all.”

Because more people opened, it raised more money than any other email. The bias Obama used here is the curiosity gap. We’re more likely to act on something when our curiosity is piqued.

Loss aversion, social proof, consistency, scarcity and curiosity—all these nudges have helped me improve my emails. And I reckon they’ll work for you.

It’s not guaranteed of course. Many might fail. But running some simple a/b tests for your emails is cost free, so why not try it out?

This blog is part of Phill Agnew’s Marketing Cheat Sheet series where he reveals the scientifically proven tips to help you improve your marketing. To learn more, listen to his podcast Nudge, a proud member of the Hubspot Podcast Network.