Kellerman (1977) explained these phenomena by the principle of psychotypology. He argues that second language learners instinctively judge degrees of similarity between languages they know already and their target language. Where they perceive similiarity, they are more likely to transfer existing knowledge. In particular, they will borrow lexical items and will assume that similar sounding words have similar meaning. For example, Ringbom quotes a Swedish L1 learner using the word piggy to mean 'refreshed' in English. The learner had assumed that the Swedish word pigg (refreshed) could simply transfer into English with the simple addition of the -y adjective marker. Singleton's Philip picked up on the French time adverbial depuis (since) and assumed it had the same meaning as the Spanish despues (after). In this case, there is probably greater similarity between Philip's L1 after and the target language après, but Philip confirms Kellerman's principle by preferring to draw on knowledge of a language perceived as more close to his target.