ACT is based on the theoretical foundation of relational frame theory (RFT), developed by Hayes. With roots in radical behaviorism, RFT starts with the premise that language and cognition are learned, along with a set of relationships between phenomena, called relational frames. An example is the comparative and evaluative frame, which links things together with terms such as better than, bigger than, and prettier than. Although they are first learned in a specific context, these relations can be established and generalized even without direct experience; that is, humans can learn by observing or through language. We can also transfer this learning to other situations or, in ACT language, contexts. We begin to learn these relationships as babies, and never stop learning such associations; we accumulate relations.