Previous studies have empirically shown that learning multiple related tasks simultaneously can significantly improve performance relative to learning each task independently, especially when only a few labeled data per task are available (Caruana, 1997;Bakker and Heskes, 2003;Argyriou et al., 2006).
given the limited labeled review data for each domain, we formulate the review spam detection tasks for multiple domains, e.g., hotel, restaurant, and so on, as a multi-task learning problem.