Reflecting on the use of response times to index linguistic knowledge in SLA

Response times (RTs) have become ubiquitous in second language acquisition (SLA) research, providing empirical evidence for the theorization of the language learning process. Recently, there have been discussions of some fundamental psychometric properties of RT data, including, but not limited to, their reliability and validity. In this light, we take a step back to reflect on the use of RT data to tap into linguistic knowledge in SLA. First, we offer a brief overview of how RT data are most commonly used as vocabulary and grammar measures. We then point out three key limitations of such uses, namely that (a) RT data can lack substantive importance without considerations of accuracy, (b) RT differences may or may not be a satisfactory psychometric individual difference measure, and (c) some tasks designed to elicit RT data may not be sufficiently fine-grained to target specific language processes. Our overarching goal is to enhance the awareness among SLA researchers of these issues when interpreting RT results and stimulate research endeavors that delve into the unique properties of RT data when used in our field.