 Little or no progress was made for the next 25 years dominated by the selective search paradigm.The best program produced during this time was Mac Hack VI in 1967; it played at the about the same level as the average amateur (C class on the United States Chess Federation rating scale).In 1974, another search paradigm was implemented for the first time in the Northwestern University Chess 4.0 program, the alternative described in Shannon's 1949 paper, called full-width or "brute force" searching.