On the Proper Treatment of Noun-Noun Metaphor: A Critique of the Sapper Model

This paper responds to the claim of Veale, O’Donoghue and Keane (1995) that SME (Falkenhainer, Forbus & Gentner, 1989; Forbus, Ferguson & Gentner, 1994) performs poorly on noun-noun comparisons, such as A surgeon is like a butcher. Veale et al. argue that such noun-noun comparisons involve “object-centered representations” that do not contain higher-order relations, and that Sapper’s chaining of expressions that share entity arguments provides a better model than SME for such comparisons. They also literally claim that SME will require longer than the lifetime of the universe to align Sapper’s noun representations. We refute both their cognitive and computational claims here, focusing on (1) the psychology of noun-noun metaphors; (2) how Sapper works; and (3) SME’s actual performance.