Abstract
This paper reports two experiments that investigated the semantic distance model (SDM) of relevance assessment. In the first experiment graduate students of mathematics and economics assessed the relevance relationships between bibliographic records and hierarchies of terms composed of classification headings or help‐menu terms. The relevance assessments of the classification headings, but not the help‐menu terms, exhibited both a semantic distance effect and a semantic direction effect as predicted by the sdm. Topical subject expertise enhanced both these effects. The second experiment investigated whether the poor performance of the help‐menu terms was an experimental design artifact reflecting the comparison of terse help terms with verbose classification headings. In the second experiment the help‐menu terms were compared to a hierarchy of single‐word terms where they exhibited both a semantic distance and semantic direction effect.