From the 1970s, a number of critiques of the positivism now associated with geography emerged. Known under the term 'critical geography,' these critiques signaled another turning point in the discipline. Behavioral geography emerged for some time as a means to understand how people made perceived spaces and places, and made locational decisions. The more influential 'radical geography' emerged in the 1970s and 1980s. It draws heavily on Marxist's theory and techniques, and is associated with geographers such as David Harvey and Richard Peet. Radical geographers seek to say meaningful things about problems recognized through quantitative methods, provide explanations rather than descriptions, put forward alternatives and solutions, and be politically engaged, rather than using the detachment associated with positivists. (The detachment and objectivity of the quantitative revolution was itself critiqued by radical geographers as being a tool of capital). Radical geography and the links to Marxism and related theories remain an important part of contemporary human geography (See: Antipode). Critical geography also saw the introduction of 'humanistic geography', associated with the work of Yi-Fu Tuan, which pushed for a much more qualitative approach in methodology.