> Putting a hand on my back isn't going to make me prefer the food I'm here for. Perhaps you're immune to the effect, since you know about it. But in aggregat

> Putting a hand on my back isn't going to make me prefer the food I'm here for. Perhaps you're immune to the effect, since you know about it. But in aggregate, it can change the disposition of customers (measured using the metric of increased tips). They wouldn't do it if it didn't work.