Mixed Signals is Erin Straza’s weekly musing about marketing miscellany in advertising, branding, and messaging.

Math isn’t my thing. That’s because numbers don’t make sense to my word-wired brain. So when it comes to making purchase decisions, I am drawn to sale signs (lower prices listed right there, before my very eyes) and what I think I should have to pay for an item (like an automated spending matrix built into my brain). It’s not mathematically sound. But this is how I’ve gotten through thousands of purchase decisions over the course of my life—so far, so good.

I’ve always assumed everyone else has a math brain, able to crunch numbers and make in-the-moment substantive rationales for their purchases. That’s a big no, according to an article by Derek Thompson titled “The 11 Ways That Consumers Are Hopeless at Math” and posted at The Atlantic.

He posits that most consumers do make purchase decisions based on numbers—but not necessarily the number as it relates to the actual price. It’s more about how those numbers make us feel about the purchase. Thompson explains how this works:

First: Consumers don’t know what the heck anything should cost, so we rely on parts of our brains that aren’t strictly quantitative. Second: Although humans spend in numbered dollars, we make decisions based on clues and half-thinking that amount to innumeracy.

This is classic consumer behavior. The consumer brain is ever working to justify the choices made, to purchase or not to purchase. We collect information that supports the decision we want to make and discard the information that reflects negatively upon our decisions to assuage cognitive dissonance.

The good news is that marketers are working with us. They want us to feel great about purchasing—not because they are concerned for our mental health, but because our positive affect means sales for them. So they give us the cues we need to feel good. Thompson mentions our “obsession with the number 9”—it convinces us of a great deal. He also pinpoints our desire to avoid extremes—“we don’t like feeling cheap, and we don’t like feeling duped”—so we are drawn to product with a mid-range price point.

What do we do with this news? As I processed the tenets of Thompson’s article, I was forced to acknowledge anew my capacity to be swayed by the whims of others. Marketers obviously know how to influence me. But I also admit that my internal spending matrix was constructed in U.S. society, heavily influenced by the spending values of our culture. What I have deemed appropriate purchase behavior for the States would be disgustingly wasteful in other countries.

Numbers are not my thing, but I don’t want to default to my own level of righteousness when it comes to my purchase behavior. This is where I need lots of grace for my consumer mindset as well as plenty of conviction to live my life by the Spirit’s leading rather than the siren cry of a supposedly good deal.