"They are not looking at the natural aspect of food.

VOA: standard.2010.02.23

So, you could train a pigeon to peck for food but that's because pecking for food is a very natural response.

你可以训练鸽子啄食,但这只是因为啄食是种自然反应而已。

耶鲁公开课 - 心理学导论课程节选

Well the cockroach is pretty much its natural state and you have all the ingredients in the other food.

而蟑螂则保持了自然形态,奇多的所有配料

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

With no natural predator in the water, and almost no domestic market to sell them as food, Asian Carp threaten to expand into waterways through the city of Chicago, and into Lake Michigan, about 320 kilometers northwest of Havana.

VOA: standard.2010.07.20

It's usually colored because there's food dye in it, but it wouldn't be colored in its natural state.

通常是五颜六色的,因为其中含食用色素,但在自然情况下,它是无色的

耶鲁公开课 - 生物医学工程探索课程节选