A study used two auditory tests of reaction time to compare second language learners' and native speakers' detection of ambiguity or acceptability of sentences. The subjects were Finnish learners of English as a second language and native English-speakers. The investigation found that Finnish-speakers' reactions were generally similar to the native speakers' with the exception of the time taken to make judgments. The native speakers appeared to have immediate access to meaning through context, while the nonnative speakers may have had to resort to problem-solving strategies, taking significantly more time. There were also clear differences between individual Finnish subjects, reflecting English proficiency. Sentences using material learned either early or late in the language learning process required more processing time than those using material learned in between, suggesting that the hierarchy of learning difficulty cannot be equated with the hierarchy of processing difficulty. Native speakers were generally more unanimous in their decisions. For sentences ambiguous to natives, the Finnish subjects could see only one possible interpretation, the more basic or common one. However, it is noted that the apparent simplicity of these findings does not necessarily reflect responses in real-life interactional situations. Tables and figures are included. (MSE)