NEW YORK – A new University of Pennsylvania study delves into what consumers believe is “enough” to satisfy their appetites, citing new evidence that suggests how much people eat depends on what’s put in front of them.

“Whatever size a banana is, that's what you eat, a small banana or a big banana,” said researcher Andrew Geier at the University of Pennsylvania, noting, “whatever's served on your plate, it just seems locked in our heads: that’s a meal.”

The Associated Press writes that, according to Geiger, consumers learn portion size from their cultures, noting that in France, yogurt containers are “a bit more than half the size” of American yogurt containers. However, French consumers “don’t make up the difference by eating more containers of the stuff,” he commented.

Geiger and his team experimented with the theory of “unit bias” by placing a large bowl filled with one pound of M&Ms in the lobby of an apartment building along with a sign saying, “Eat Your Fill” and to “use the spoon to serve yourself.” Researchers swapped the spoon sizes from a tablespoon to a quarter-cup over a 10-day period, and found that on days where the larger spoon was available, people consistently took more M&Ms than on days where the spoon was smaller.

However, one of Geiger’s experiments did show that his theory of unit bias has its limits. On his home turf, he had one dining hall provide 10-ounce glasses for soft drinks while another provided 16-ounce glasses. He predicted the students offered the smaller glasses would drink less, only to find that they drank more. So what went wrong?

“They were taking two [10-ounce] glasses at a time,” Geiger told the AP, adding, “I guess I went below what is culturally construed as a unit of soda.”