Email marketing delivers clickthrough rates that are up to six times higher than that of social and generates the highest ROI of any marketing channel.

But an email is only as good as the content it contains.

Users spend just 11.1 seconds reading an email, on average; images, therefore, play a vital role in grabbing attention and communicating the right message. As the age-old adage goes, a picture is worth a thousand words.

But how do you choose the right image? How can you be confident that it will generate results? What are some real-life examples of effective and informed image selection?

The Importance of Images

Pictures are a universally understood language. They draw our eyes before anything else, and they can increase the inclination to read a piece by 80%. Customers themselves say they prefer and focus on images over text.

Images also help us remember information. After three days, people are likely to retain just 10% of the information they have consumed; but when the information is combined with a relevant image, they remember six times more, according to a study by John Medina.

Selecting the Right Image

With an abundance of images available to marketers today, it can be difficult to know where to start. How bright should it be? Should it have a particular hue? What themes or activities should it depict? Should it have people in it? If so, how many?

To start answering such questions, we need to understand what makes an image more or less appealing and under what conditions. Of course, A/B and multivariate tests can play an important role, but they tell us only that a particular image works better than another—not why they do. Knowing that is essential for taking lessons learned into the future and for adopting a data-driven approach to marketing.

Enter the science of image appeal and memorability.

Subject

A study conducted by researchers at MIT found that images with people in them are the most memorable, followed by "human-scale space" (e.g., the produce aisle of a supermarket), and closeups of objects. The least memorable images were natural landscapes, unless they featured an unexpected element (e.g., shrubbery trimmed into an unusual shape).

In 2015, some of the same researchers released MemNet—a deep-learning algorithm that allows anyone to upload a photo and get a memorability rating for it (try it out here).

Color

Colors communicate messages, evoke emotions, and influence behavior. In fact, up to 90% of snap judgments about products are based on color alone. Although there is little evidence of specific colors performing universally better than others, research has found that there are gender differences in color preferences, with men preferring bolder colors and women preferring softer colors. Other studies have found that relaxing colors, such as blue, can make website actions (such as file downloads) appear more rapid and produce stronger buying intentions.

However, decisions over which colors to use come down mainly to what you want to achieve (you can see which emotions are commonly associated with various colors in the box, below). The most important thing is that a color is perceived as being appropriate for your brand and product.

As a result of evolution and culture, humans have developed certain associations with colors:

• White: purity, cleanness, simplicity, hygiene, clarity, peace
• Yellow: cheerful, optimism, extraversion, friendliness
• Pink: sincerity, nurturing, warm, soft
• Red: excitement, arousing, exciting, stimulating
• Orange: arousing and exciting, lively, energetic, extroverted, sociable
• Blue: competence, intelligence, communication, trust, efficiency, duty, logic
• Brown: seriousness, reliability, support
• Back: sophistication and glamour, power, stateliness, dignity
• Purple: luxury, authenticity, quality
• Green: nature, security