When you see that bright-red McDonald's roof, do you get hungry?

The going popular theory is that brands like McDonald's and Burger King use the color red in their logos and around their stores because it revs up people's appetites, making them hungry, which therefore makes them more likely to enter the store and then buy more food while they're in there.

Here's what it looks like when you search for fast food logos:

Google Images/Tech Insider

Lots of red, right? You'd think there's gotta be a reason for this, but actually this belief doesn't seem to have much actual grounding in science.

Like a lot of psychological science, the question of whether the color red makes people want to eat more is hard to answer with a simple yes or no.

Studies have shown that red is stimulating, exciting, and associated with activity. That doesn't necessarily mean that it makes you hungry, though.

The color red can also increase our heart rates, which could be the reason why countless media reports have said it can jump-start our appetite. But heart rate and appetite aren't necessarily linked. It's more likely that the color has just become synonymous with fast food over time, perpetuating the idea that red makes you hungry.

Actual studies seem to say the opposite.

In lab studies, participants drank less soda from a red cup than from a blue cup and ate fewer snacks that were on a red plate than ones on blue or white plates. Like many of these experiments, the number of subjects in this one, published in the journal Appetite, was low — only 41 participants were in the soft-drink portion and 130 were in the food portion.

And in a bizarre follow-up study also published in Appetite, researchers found that participants preferred to eat snack foods or apply moisturizing cream — yes, you read that right — from plates that weren't red.

That doesn't mean that the brand's color isn't important. The color of a sign or recognizable logo can be an important factor in quickly choosing to buy a product.

People can make 62% to 90% of their snap decisions about products based on color alone, according to a 2006 study in the journal Management Decision.

What it really comes down to is that our attraction to the red color of signs is most likely derived from our experiences linked with the color or brand.

If we have happy memories or associations with the color red — like the happy feeling of getting to stop at Dairy Queen for a cone after a Little League win, for example — we might happen to crave ice cream and feel happy when we see the red logo.

But the science on the topic, unfortunately, is still unsettled.

While it may be that brands color their signs red to make them stand out or be memorable, it doesn't seem like these bright colors actually make us hungrier or likely to eat more.