Social presence (represented by salience of instructor and fellow students) in an online teaching environment has been shown to influence perceptions of course activity and self-estimates of learning. An experiment is described here in which teacher presence is manipulated via personalized messages from the teaching assistant throughout the course. High presence was not associated with activity in class discussion, homework performance, or tests over the assigned readings. It is suggested that these results have clear implications for the interpretation of research using perceived as opposed to objectively measured course outcomes to evaluate social presence and teacher immediacy concepts.