The LSA holds a four-week biennial Linguistic Institute in the summer which includes talks and coursework on various aspects of linguistics. Considered by the membership to be one of the most important services of the LSA,[17] the Institute has helped influence the development of the field through promotion of new directions such as psycholinguistics and sociolinguistics.[18] Each Institute features a number of endowed Chairs named after prominent linguists: the Sapir chair in general linguistics,[19][20] the Collitz Chair in historical linguistics,[21] and since 2005, the Ken Hale chair in linguistic fieldwork and the preservation of endangered languages.[22]