One of their most recent publications is Effects of performance feedback valence on perceptions of invested mental effort. Which was published in journal Learning and Instruction.

More information about Steven F. Raaijmakers research including statistics on their citations can be found on their Copernicus Academic profile page.

Effects of performance feedback valence on perceptions of invested mental effort

Highlights•3 experiments showed that feedback valence affected perceptions of invested effort.•Perceived mental effort was higher after negative than after positive feedback.•We replicated that overall effort ratings were higher than task-specific ratings.•Overall and task-specific effort ratings were both affected by feedback valence.•Thus, mental effort is best measured directly after each task, before giving feedback.