At their heart, marketing and sales are about connecting. That means you always need to plug into your brand's humanity and authenticity. When you do that, you'll draw more people in, create stronger connections and ultimately sell more.

Want to accelerate that process? Who wouldn't? By applying a few tried-and-true psychology principles, you can better understand and influence your followers. And best of all, these tips can be applied to any demographic.

Use these three takeaways from psychology studies to enrich your marketing efforts.

1. Don't stop

The gist: The more people see you, the more familiar they become, and the more they like you! In 1968, Robert B. Zajonc showed people symbols that looked like Chinese characters. 11 out of 12 times, the more they saw the character, the more they liked it. This is known as the mere-exposure effect.

How you can use this: Communicate with your followers and customers regularly. Creating and sticking to a content calendar is the easiest way to make this happen. Then, keep the goodwill going. Highlight one product for a week (or longer).

By eliminating choices and focusing on a single item, people will learn to like that product more, and it doesn't overwhelm them with options, which makes it easy for them to hit purchase.

2. Give a little to get a lot

The gist: If you give someone something for free, they feel obligated to return the favor and give something to you. Back in 1974, Phillip Kunz put this principle to the test. He sent out 600 Christmas cards to random strangers, which made 200 people mail him a card in return.

How you can use this: Promote that you'll include a small freebie every purchase. Say you'll give away samples of your product to the first 500 people who share their contact and mailing address. Mail everyone in your system a thank-you card. There are so many ways you can capitalize on reciprocity.

Get your team together, brainstorm what you could give away to a mass amount of people at a low cost and promote the heck out of it. Those people will want to do something for you in return, so follow up with them after the fact. Send them an email asking if they enjoyed your free gift and give them a discount code for future purchases.

3. Make it urgent and limited

The gist: People hate to miss out. When retailers release limited numbers of goods and buyers are aware of this, they want to buy as quickly as they can to avoid regret later. PlayStation often does this, and when done right, this study shows it works.

How you can use this: To build frenzy, release limited amounts of product. Think about the success Target has had with its designer collections.

It may make sense for your business to integrate this tactic into your product planning or production. Or in the short term, you can put limited quantities of a product on sale. And when you're almost out of an item, create a marketing blitz to quickly move what's left.