In one of his articles, Liberman mentioned speech production is easy to create as it relies on the "conscious awareness of phonological structure". He disagreed with "horizontal theory" because it would imply that the "advantage of ease" would be dependent upon reading and writing, not speech. Liberman also argued that reading alphabets is not important to speech until one learns the phonological pattern of speech. He made mention that speech itself is not only attributed to biological evolution, rather it is also species specific.