Methods and apparatus to detect user attentiveness to handheld computing devices are disclosed. An example handheld computing device includes means for detecting at least one of a first orientation change of the handheld computing device or a first position change between the handheld computing device and a user, and means for comparing at least one of the first orientation change or the first position change to a plurality of spatial condition change combinations associated with respective likelihoods indicative of user attentiveness related to the handheld computing device to determine user attentiveness to a presentation on the handheld computing device, the plurality of spatial condition change combinations including a plurality of orientation changes from respective starting orientations to respective ending orientations and a plurality of position changes from respective starting positions to respective ending positions.