Abstract: In a method of estimating Internet activity dependence of a human subject, a respiration sensing unit senses respiration-caused thoracic and abdominal movements of the human subject during a first time period, and a subsequent second time period during which an emotion stimulating material played on a multimedia playing unit is being watched by the human subject so as to generate two sets of thoracic and abdominal respiratory signals corresponding respectively to the first and second time periods. A processing unit generates an estimation result associated with the Internet activity dependence based on the emotion stimulating material and the sets of thoracic and abdominal respiratory signals.