  This study explores the impact of peer acknowledgement on learner engagement
and implicit psychological attributes in written annotations on an online
social reading platform. Participants included 91 undergraduates from a large
North American University. Using log file data, we analyzed the relationship
between learners' received peer acknowledgement and their subsequent annotation
behaviours using cross-lag regression. Higher peer acknowledgements correlate
with increased initiation of annotations and responses to peer annotations. By
applying text mining techniques and calculating Shapley values to analyze 1,969
social annotation entries, we identified prominent psychological themes within
three dimensions (i.e., affect, cognition, and motivation) that foster peer
acknowledgment in digital social annotation. These themes include positive
affect, openness to learning and discussion, and expression of motivation. The
findings assist educators in improving online learning communities and provide
guidance to technology developers in designing effective prompts, drawing from
both implicit psychological cues and explicit learning behaviours.
