I've just ordered 48 rolls of toilet paper from a brand I've had my eye on for a while. It has strong sustainability credentials and highly rated products. But until now, I hadn't got further than browsing the website. Today, I finally clicked the "buy" button. And, thanks to my podcast interview with author and marketing consultant Matthew Willcox, I've got a pretty good idea why.

In his book, "The Business of Choice: How Human Instinct Influences Everyone's Decisions," he digs deep into "behavioral insights." In other words, how unconscious instincts can sometimes nudge us to choose one thing over another.

How Does Human Instinct Sway Choice?

Willcox works in marketing, where this knowledge can help organizations sell products and services. But he believes that understanding how our instincts dictate our choices can be useful to anyone.

In this clip from my Expert Interview podcast, Matthew Willcox explains the importance of understanding how human instinct can sway the decisions that we make.

Looking at my toilet paper purchase through a behavioral science lens, I can see a few instincts at play.

For a start, there's what Willcox calls "Social Proof." This is when we're encouraged to do something because other people are doing it. One example Willcox references is how the U.K. government persuaded more people to pay a hard-to-collect tax by sending them a letter stating that similar folks had paid it on time.

I bought my toilet paper with a £5 discount voucher sent to me by a friend. She also got £5 off her next purchase. Not only did this give us a sense of togetherness in our choice of brand, it also had a little financial perk.

Positioning the Consumer as Expert

Getting a bargain made me feel positive about my purchase, and this speaks to a fundamental human instinct – our desire to feel good. There are lots of ways for marketers to achieve this, according to Matthew Willcox. From the age-old tactic of offering discounts, to using quizzes and surveys, which makes consumers feel more like experts.

For me, the toilet paper brand's sustainability credentials made the most difference. The product is 100 percent recycled, and 50 percent of the profits go toward building toilets in communities where they're needed. This boosted the "feel-good" factor of my purchase. It also wrapped in another behavioral insight: we're hardwired to compare.

"If you put us in front of one washing machine and you ask us to assess its capabilities, we do...