Scarcity Effect

Researchers presented students with two types of cookies : chocolate chip ones (said to be rare) and raisin ones (abundant). 

Even though some students said they preferred raisin cookies, they choose the chocolate chip ones.

Scarcity influences our decisions, making us value things more just because they are harder to obtain.

See the full study here :

Worchel, S., Lee, J., & Adewole, A. (1975). Effects of supply and demand on ratings of object value. Journal of Personality and Social Psychology, 32(5), 906–914.

Want to know more about biases?

Automation Bias

The Less is Better Effect

Lag Effect

Curse of Knowledge