Analogy is a cognitive process that transfers meaning from one subject to another, often based on similarities. It plays a role in many functions like problem solving, memory, and communication. Examples of analogies include "bedroom is to sleeping as kitchen is to cooking" and "plant is to carbon dioxide as human is to oxygen." Transfer of learning refers to how prior experiences impact future learning or performance. Early theories proposed that transfer depends on how similar the original and new tasks are. Theories of transfer include mental discipline theories, identical elements theories, and generalization theories.