The recognition effects of attribute ambiguity.

When examining memory effects of semantic attributes, it is common practice to manipulate normed mean (M) ratings of the attributes (i.e., attribute intensity) in learning materials. Meanwhile, the standard deviations (SDs) of attribute ratings (i.e., attribute ambiguity) are usually treated as indexes of measurement error. However, some recent research found that recall accuracy varied as a function of both the intensity and ambiguity of semantic attributes such as valence, categorization, concreteness, and meaningfulness. These findings challenged the traditional interpretation of attribute rating SDs as noise indexes. In the current study, we examined the recognition effects of ambiguity, intensity, and Ambiguity × Intensity interactions for 21 attributes using mega study data for over 5,000 words. Our results showed that attribute ambiguity had reliable recognition effects beyond those of attribute intensity, and that it sometimes explained more unique variance in recognition than attribute intensity. Thus, we concluded that attribute ambiguity is a distinct psychological dimension of semantic attributes, which is processed separately from attribute intensity during encoding. Two theoretical hypotheses had been proposed for the memory effects of attribute ambiguity. We discuss the implications of our findings for the two theoretical hypotheses about how attribute ambiguity influences episodic memory.