According to Cummins, knowing one second language can Proficiencybilingualismcommonhelp you learn another. CUP stands for Common Underlying Proficiencybilingualismcommonhelp. The Linguistic Interdependence Hypothesis states that every language contains Proficiencybilingualismcommonhelp features. Additive Proficiencybilingualismcommonhelp states that developing proficiency in a second language helps develop proficiency in the first language.