Optimal-level theories maintain that the quality of affect is a function of a quantitative arousal potential dimension. An alternative view is that the quantitative dimension merely modulates preexisting qualitative properties and is therefore only responsible for changes in the degree of affect. Thus, the quality of affect, whether it is positive or negative, has to be treated as an independent variable. In an experiment to compare these alternatives, the quantitative dimension was measured by varying the degree of unexpectedness of endings in stories that were overall either positive or negative. Contrary to predictions of optimal-level theory, the results showed that differently valanced story endings, judged the same on an expectation scale, were rated very differently in hedonic tone and preference by high school readers. (Author)