Empirical studies have revealed that teachers face problems when assessing task difficulty for their students. By drawing on research that focuses on how individuals assess what others know, we argue that these difficulties are a consequence of the imputation of one's own knowledge to others (i.e., social projection). In particular, we tested the assumption that individuals impute more of their own knowledge to others, the more they elaborate what these others might know. In a first experiment, students were asked to judge task difficulty for their best friend. In the second experiment, teacher trainees were asked to assess task difficulty for 9th graders. Results revealed that individuals, who deeply elaborated when assessing task difficulty for another person, more closely relied on their own rating of task difficulty than individuals with a lower elaboration depth. These findings support the notion that social projection becomes stronger, the deeper individuals elaborate.