Two competing hypotheses about speech processing were examined in two experiments. The hypotheses were that: (1) people rely on the configurational properties of sentences in relative clause (RC) processing; and (2) people rely on the grammatical roles of the noun phrases involved in relativization in RC processing. The first experiment used a comprehension task to test native speakers of Spanish, a VO language, learning Basque, an OV language. The results provide strong support for the idea that the configurational properties of sentences play a crucial role in language processing, as opposed to the idea that it is the grammatical relations holding between elements of a sentence that affect the relative difficulty of processing . The second experiment tested native speakers of English, a VO language, learning Spanish, another VO language. This experiment, while failing to provide support for either hypothesis, raised an interesting theoretical issue: that when parameters have to be reset in the second language learning, acquisition is hindered considerably. (MSE)