The document discusses the semantic differential scale (S.D. scale), which was developed by Osgood, Suci, and Tannenbaum to measure psychological meanings of objects. The S.D. scale is based on the idea that objects have multiple connotative meanings that can be located in a multidimensional "semantic space." It uses bipolar rating scales, usually 7 points, for respondents to rate concepts. For example, leadership candidates could be rated on scales like "successful-unsuccessful" to analyze meanings. The S.D. scale aims to measure three factors - evaluation, potency, and activity - that contribute most to meaningful judgments.