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What Nobody Tells You About A/B Subject Line Testing

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by: Heather Simerly (@IBMforMarketing)
01 July 2016

Have you ever wondered why some subject lines grab readers’ attention while others fall flat? As a marketer, you surely do! This month, we’re excited to have business partner Three Deep Marketing tell us about the science of the brain and what nobody tells you about A/B testing.

Dave Woodbeck, Three Deep MarketingAs marketers, we have an intuitive sense of why subject lines matter — they get people to open and click on the email. But how do they work? What is it about human nature and the science of the brain that makes them work?

This is a much longer topic, but we’re going to cover it in short order. The brain has two fundamental states of awareness:

  1. Alpha: a state of autopilot
  2. Beta: a state of alertness

The Reticular Activator (RA) controls what wakes up the brain and moves it from Alpha to Beta. The RA is constantly on the lookout for things that are familiar, problematic or unusual. When it observes anything of that nature, it will snap your brain from Alpha to Beta. Subject lines need to do that exact same thing. They need to snap the RA from Alpha to Beta, so your prospect will actually pay attention.

Subject Lines – The Ad for the Ad

Without a compelling subject line, all your hard work to construct an email is wasted. The key to writing good subject lines is to match up your prospects’ hot buttons to the content you’re planning for your email (hopefully you’ve already completed a content strategy that has done this and created a strong editorial calendar).

You’ll want to create subject lines that have enough contrast to them to be meaningful. Too often we’ve seen subject line tests that aren’t distinctive enough from each other to gain any valuable performance lift, or just as importantly any learnings about your audience!

For example, you might be wondering which subject line will increase more back-to-school haircuts from your database. Many email marketers will go directly to the promotional subject line, but before you just start giving promotions, think about what you could learn about your audience and how to inject a stronger value equation to your consumer.

Remember the great line in Austin Powers when Fat Bastard says “Get in my belly”? Well, as marketers we need to “Get in my brain.” In other words, start thinking about the conversation that is happening in your consumer’s mind:

  • “I sure would like to get Johnny a stylish haircut that both he and I will love.”
  • “What haircut styles don’t make my kid look like a dork?”
  • “I just don’t want to hassle with thinking about this, can someone just give me good advice?”

The exercise really helps you to understand how you’re going to hit that hot button and get the consumer to flip their brain from Alpha to Beta. Using our Revolutionary Guide to Writing Effective Headlines, you can rapidly start to create headlines that will be more compelling to your consumers, and you’ll be able to categorize them. Here is an example of some subject lines you could use:

  • 3 Easy Hairstyles That You and Your Kid Will Love
  • How to Get Free Compliments with Your Kid’s Next Haircut
  • The Ultimate Guide to Your Child’s Hair Style

Notice how these subject lines go beyond promotion by trying to tap into the hot buttons that we derived from getting in our customer’s brain.

Don’t Just Use Math for Your Testing, Use the Science of the Brain

The above principles of brain science should give you a new understanding of why and how you can test subject lines to gain better results.  Yes, the math behind testing is still critical, but putting a little thought into why the brain makes decisions can give your testing a large leap forward in its effectiveness. You’ll even find some true insights into how your prospects behave!

Three Deep is a solution-focused digital marketing agency specializing in acquisition and lead generation-based campaigns as well as behavioral-based triggered email campaigns for customer nurturing. Three Deep’s core purpose is helping businesses grow through measurable digital marketing programs. For more info, visit

Get More Email Ideas:

1) Tip Sheet: “Transactional Emails: 10 Tips for Driving Value and Engagement

2) Blog: “Beyond Preferences: How to Appeal to the Inherent Nature of Your Customers

3) Ebook: “15 Post-Purchase Emails That Build Loyalty and Drive Revenue


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