The country-mapping study explored how analogical mapping can sometimes generate one-to-many and many-to-one mappings in addition to the common one-to-one mappings (Spellman & Holyoak, 1996). In the study, subjects mapped countries from a source story to a target story where one mapping was ambiguous -- namely, one country in the source story could map to one of two countries in the target story. Spellman and Holyoak reported that while one-to-many mappings were rarely produced, many-to-one mappings were frequently produced.
The country-mapping model simulates subject performance in this task and produces the results reported by Spellman and Holyoak. The model iteratively maps each source country to an analogous target country. The results, presented as proportion of one-to-many and many-to-one mappings produced, report that many-to-one mappings occur approximately half the time while one-to-many mappings never occur.