Contextual Effects in Category Ratings

In sensory evaluations of consumer products, panels of observers often use ratings on category scales to assess differences in the sensory characteristics of products. However, use of rating scales, especially by naive observers, is prone to several biases that may act to distort such judgments. Observers learn about the range and distribution of sensory values for a given characteristics, and then adjust their judgments of that characteristic so that a full range of the available categories are assigned, and so that the categories are assigned with roughly equal frequency. Unless trained and given a constant frame of reference, observers use category scales as relative, not absolute, scales of judgment, adjusting their internal strandards based upon the recent contexts within which a product was presented.