As a child, one of the big memories of the ride on Interstate 70 to Columbia, Mo., to watch the University of Missouri Tigers football team lose on a Saturday, was the sign for a barbecue restaurant in Concordia, Mo.

We never ate there. Dad was always in too much of a hurry to get to the game on the way to Columbia, and always had enough beer in him that he just wanted to get home on the way back. That’s a shame because this restaurant was supposed to have had pretty good food.

The sign featured a dopily grinning cow and a bright pink pig that looked like someone just told him he’d won tickets to see his favorite band (that plays whatever kind of music pigs enjoy).

I remember wondering, why do these animals look so happy? Growing up on a farm, I always knew where my food came from. Didn’t this happy cow and pig realize what was going to happen to them? They were going to become a whole lot of sandwiches.

I hadn’t thought about that sign for a long time, until I saw an ad on the Internet for the Pig Roast Veggie Fest in Narrowsburg, N.Y., featuring an anthropomorphic smiling pig slicing off bits of its own stomach with a meat cleaver. It’s not only disturbing, it’s non-hygienic. Like the long-ago smiling cow and pig, this animal just looked so darned happy to be eaten.

This theme is common in restaurants. I’ve seen similar pictures on chicken restaurants, hamburger restaurants, vegan restaurants because vegans have never figured out how to properly make their point, and an endless number of barbecue joints.

The reason? Smiles are powerful.

Studies have shown smiling makes a person happier, healthier, more likeable, trustworthy, wealthier, and people remember them more than they do someone who’s frowning. Smiling people also have a lot more sex than someone who’s grumpy, like Dr. Zaius from “Planet of the Apes.” Of course when it comes to sex, a person smiling also has the benefit of not being a 67-year-old British guy in an orangutan costume.

But why apply this to a sign for a restaurant that’s going to feed you these smiling animals? Because the advertising gods know:

1. Smiles are friendly, even from animals doomed to die.

2. Smiles make others (people and apparently pigs, etc.) smile, too.

3. Smiles mean these animals are popular and can make lots of new friends who are going to eat them.

4. Smiles stick in people’s memories (even after more than 30 years).

And, 5. Smiles mean good health despite the fat content of the average beef brisket.

Despite the facts that behavioral science, marketing research, and a 4-7 p.m. happy hour are pretty alluring, signs like this still make me nervous. Offutt Food Rule No. 27: Never trust a smiling pig.

Follow Jason Offutt on Twitter @TheJasonOffutt.