A good marketer knows how to nudge. Nudging works on everyone, but it’s especially effective on millennials whose brains are trained to filter the more obvious tactics that work on impressionable baby boomers. Let me explain. When a millennial sees “75% off” they know you just quadrupled the price and slapped a SALE sticker on there, but a baby boomer gets a little dopamine kick and starts musing on all the money they’re about to save on something they weren’t even planning on buying thirty seconds ago.

With millennials, you have to make them think they discovered the value on their own. You have to nudge them. The first time I was aware of nudging as a premeditated, conscious action was when I was in college and this girl named Brittany was trying to get me to kiss her. We were face-to-face, and she subtly squeeze-tugged my upper arm in her direction. I think I actually assumed a pensive expression as I made the connection between that outside force and how I was naturally inclined to respond. Then she did it again, slightly more forcefully, and I was on to her. I found out later that lots of girls knew this trick, and used it with great efficacy.

Now, that’s a physical nudge, and it’s the namesake for virtual or subliminal nudging. But the concept is the same, and all types can be extremely effective at getting people to do what you want them to do, even if you’re on to them.

A few of my favorite nudging instances were brought to my attention by John Daly at the University of Texas at Austin.

The pee fly

Airport janitorial workers somewhere in northern Europe–probably Sweden–were sick and tired of wiping pee off the walls around the urinals. Anyone with little boys at home can surely sympathize. Big, bright signs saying “aim your damned pee stream”, or something to that effect, proved fruitless (except probably on baby boomers). But when they painted a tiny fly in the center of the bowl, suddenly every male who came through was focusing their trajectory with laser-like intensity. The cost: some paint.

The slow stripe

Apparently there was an elevated freeway in Chicago with a very dangerous curve. A glass building just beyond the bend would reflect sunlight in drivers’ eyes at certain times of the day and year, and cars were shooting off the thoroughfare like slot cars, and according to sources, this was undesirable. All they really needed was for people to slow down, but everyone knows that nobody pays any attention to speed limit signs, especially when they can’t read them on account of the glare in their eyes. So the authorities painted lateral white lines across the entire road, a given distance apart. As the lines approached the dangerous curve, they got closer and closer together, giving drivers the impression that they were moving faster and faster. Knee-jerk response: lay off the gas. Deaths averted. The cost: some paint.

Nudging is about affecting someone’s behavior with a subliminal guide. When we build websites, we nudge people into buying something by making the Buy Now button the thing on the page that looks the funnest to click. When we’re trying to close a sale, we say something to the effect of “cash or charge?” No pressure, just an opportunity. In either case, they have the option to not buy anything at all. But we try not to call attention to this fact.

So how do we apply these principles to make our own lives more full? Well, our four straw haired children go into our room and mess with our stuff–my change tray, the wife’s lipstick, razors, neckties, you name it. No respect. I’m not afraid to use the switch, but I’m all about efficacy, and I find that the threat of corporal punishment, which has never done much to deter my actions, doesn’t work very well on my kids, either. I recently realized that my children behave in the house much like gas atoms in a container. They fly around incessantly, on seemingly random paths, colliding with each other and the walls and never stopping. If the container has a hole in it, in this case a door to the outside world, eventually one of those molecules finds that hole while careening down its course, and it winds up outside. Because gas molecules move so fast, it doesn’t take long for an entire volume of them to escape through a relatively tiny hole.

I first started noticing this comparison when grabbing something from the car. If I leave the front door open, it takes about fifteen seconds for all four children, three of whom can open doors anyway, to wind up outside. They don’t follow me out, they just happen to pass through the door as they bounce around the house. If I shut the door, they bounce off it and stay inside.

Well, there you have it. I didn’t have to punish anyone or put a deadbolt on my door (I think that’s against fire code, anyway). I just had to give my kids the opportunity to bounce off my bedroom door instead of passing through it and wreaking their destruction. I’m not sure how many parents who don’t consider themselves to be experts on human impulse have already figured this out, but sometimes you miss the forest for the trees. At any rate, our room is clean and my change tray gets fuller by the day.

Cost: less than some paint.