A study named "Ice Cream Illusions: Bowls, Spoons, and Self-Served Portions" makes the smaller dish/eat less theory definite food for thought. Participants using a large bowl ate just over 30% more than those who used the smaller bowl. And despite the fact that they helped themselves to a significantly larger serving size, they didn't think they dished out any more than the others.
I tried this little experiment myself. I popped a bag of microwave popcorn and measured out my typical serving (I had "eyeballed" what I thought was a single serving). I poured the popcorn into my usual bowl, one that is made to hold an entire bag of popcorn. I then poured what I thought was about the same amount in a smaller bowl. Out came the measuring cups. The large bowl contained over a cup more than the smaller one despite the fact that they looked like the same amount to me.
If these findings have convinced you to decrease your dish size, try using a salad plate for dinner or a dessert saucer for mini meals or snacks. Speaking of snacks, do you eat directly out of the package when you eat certain foods, such as chips? If we tend to overdo portions when using a large plate, think of how "super sized" they must be when there is no plate involved at all. Take the time to serve everything you eat into a dish, and you'll be much more likely to keep yourself in check.
Using a smaller plate or bowl may not seem like a change that makes much impact, but remember, it's the small changes that really add up. Eating just a little bit less at each meal could lead to hundreds of calories saved over the course of a week.
Wansink B, van Ittersum K, Painter J. "Ice Cream Illusions: Bowls, Spoons, and Self-Served Portion Sizes". American Journal of Preventive Medicine. 2006;31(3):24–243.