Research investigating the relationship between language and cognition (Lucy, 1992b) shows that speakers of languages with grammatical number marking (e.g. English) judge differences in the number of countable objects as more significant than differences in the number or amount of non-countable substances. On the other hand, speakers of languages which lack grammatical number marking (e.g. Yucatec) show no such preference. The current paper extends Lucy's (1992b) investigation, comparing monolingual English and Japanese speakers with Japanese speakers of English as a second language (L2). Like Yucatec, Japanese is a non-plural-marking language. Results show that intermediate L2 speakers behave similarly to the Japanese monolinguals while advanced L2 speakers behave similarly to the English monolinguals. The results (a) provide support for the claim that grammatical representation may influence cognition in specific ways and (b) suggest that L2 acquisition may alter cognitive dispositions established by a first language (L1). [Fieldwork for this study was supported by the Sir Eric Berthoud Travel Grant, awarded to the author by the University of Essex.]