This study aims to assess student motivation to provide valid responses to the PISA student questionnaire. This was done by modeling response times using a three-component finite mixture model, comprising two satisficing response styles (rapid and idle) and one optimizing response style. Each participant's motivation was operationalized as their probability of providing an optimizing response to questionnaire items. Overall, the model offered a good fit to the data. Results indicate that most responders were motivated to optimize, with a slight decline toward the end. Further, results showed a positive effect of questionnaire-taking motivation on PISA performance, suggesting a positive relationship to test-taking motivation. In conclusion, response times can be valuable indicators for assessing survey response quality and may serve as a proxy for test-taking motivation.