This is the second of a six-part series on the psychological factors behind brand loyalty and how it affects purchasing habits. See Part 1 here.

Commitment & Consistency. The principle of Commitment & Consistency is simple: If you can get your consumers to make a commitment to your company/brand, the more likely they are to purchase from you. This is where email marketing ties in. Even if there isn’t an official purchase, your chance of getting a purchase from them in the future increases.

One company that uses email marketing to its advantage is the YMCA. You opt-in to receive emails the moment you become a member. Once I signed up, I began receiving updates on events, 5K races, new classes and schedules. It kept me on my toes and excited about getting into shape. And because of their consistency in sending emails, I eventually signed up for my first Triathlon.

Warby Parker also recognizes the importance of commitment and consistency. If you’ve ever shopped with them online, you know that they have a Home Try-On offer. Select up to 5 pairs of glasses, and for free, Warby Parker will send those exact frames so you can give them a test drive. No commitment (from the customer) is necessary. And if you don’t like any of the frames you’ve picked? Warby Parker will cover the cost to ship them back. But they’re smart. A customer would likely feel guilty returning all 5 pairs without making some sort of commitment or purchase. And voilà, they’ve got their sale.

What brands have captured your attention lately? Share your favorites in our Comments.

FUN FACT: Like Toms in the last post, Warby Parker also offers a reciprocity program, matching every pair of glasses purchased with a donation to someone in need.