Chapter 4 by Mark Leikin brings us to a field born in the mid-1950s: neurolinguistics, at the same time as non-invasive research methods (such as electro encephalography), and neuro-imaging techniques in three dimensions became available. This allowed neurolinguists to analyse in situ how language functions in the brain, and especially how the brain is able to process more than one language. Recent research also points out that there are large differences across individuals, and no unique model. The approach may also be crucial to understand why language is so deeply linked to emotions.
Chapter 5 by Victor Ginsburgh and Shlomo Weber provides an overview of various types of linguistic distances (lexicostatistical, cladistic – based on linguistic trees, communication, Levenshtein phonetic, and others) that are now utilized in the economics literature to help explain trade relations, migrations, translations and the acquisition of languages, studied in Part II of the volume in Chapters 9 (trade), 12 (migrations) and 14 (patenting). The authors also discuss distances between groups of people, and the construction of ethnolinguistic diversity indices which are studied in more depth in Chapter 15.