Abstract: The existing researches have pointed out the importance of firms' feedback for motivating contributors to contribute ideas continuously in firm-sponsored, non-financially incentivized, idea-crowdsourcing communities, but none of them have focused on the impact of firms' direct expression of gratitude. Based on the motivation and incentive theory, using the second-hand data of a creative crowdsourcing community in China and applying the PWP-GT (the Prentice, William, Peterson Gap Time) model, this paper analyzes the impact of firms' direct expression of gratitude on contributors' continuous creative contributions, and the moderating effect of firms' feedback valence, the number of reviewers' positive comments and contributors' points. The results show that firms' direct expression of gratitude will motivate contributors to continue contributing ideas. When an idea receives negative feedback (versus positive feedback) from firms and more positive comments (versus less positive comments) from reviewers, the incentive effect of gratitude directly expressed by firms will be enhanced. When contributors have more points (versus less points), the incentive effect of gratitude directly expressed by firms will be weakened. This paper expands the application scenario of expressing gratitude, explores the boundary conditions of gratitude incentives, deepens the research on multi-source incentives in the online environment, and has reference value for understanding the existing gratitude strategies of firms in idea-crowdsourcing communities.

Key words: idea-crowdsourcing communities, firms' direct expression of gratitude, continuous participation, external incentives, user as innovator