An online experiment(N = 96)explored which factors encourage readers to respond in an online forum discussion about the pros and cons of alternative medicine.After indicating their attitude on this issue,participants read an online discussion containing 24 pro and con posts about alternative medicine.Thus,cognitive conflict could be computed as the distance between person and post.Furthermore,participants had the opportunity to respond to whichever post(s)they liked.Results indicated that greater cognitive conflict was associated with higher likelihood of responding.This effect was attenuated in posts with high emotionality.Finally,greater conflict was associated with longer responses.Implications for research in CSCL and social psychology are discussed.