The Rasch model for test analysis is a latent-trait model, which specifies the relationship between observable test performance and the unobservable traits or abilities assumed under test performance. In most cases, the test constructor has no clue as to whether the latent traits postulated by the model are indeed the abilities he wants to measure. A study using an English-language listening comprehension test for both native speakers and Dutch students of English as a second language has yielded data that may help to identify the ability that, according to Rasch test analysis, underlies the main trait measured by the test. (Author/MSE)