An apparatus to evaluate three-dimensional viewing experiences comprising: a processor element; and logic to: compare a first region of interest 'ROI' data associated with a first viewer of a first visual presentation of a two-dimensional '2D' version of visual content to a second ROI data associated with a second viewer of a second visual presentation of a three-dimensional '3D' version of the visual content; and identify an instance of a statistically significant difference with regard to where the first viewer's and the second viewer's gaze is directed between the first ROI data and the second ROI data for at least one frame of the visual content, indicative of an instance of viewing fatigue of the second viewer, wherein: the first ROI data is made up of three-dimensional co-ordinates for the first viewer for each frame of the 2D version of the visual content indicating the first viewer's region of interest based on correlating depth data from a per-frame depth map for pixels in each frame of the visual content with eye tracking data indicating a direction of a line of sight of a gaze of at least one eye of the first viewer; and the second ROI data is made up of three-dimensional co-ordinates for the second viewer of a convergence point for the second viewer based on eye tracking data indicating lines of sight of each eye of a pair of eyes of the second viewer for each frame of the 3D version of the visual content indicating the second viewer's region of interest. a processor element; and logic to: compare a first region of interest 'ROI' data associated with a first viewer of a first visual presentation of a two-dimensional '2D' version of visual content to a second ROI data associated with a second viewer of a second visual presentation of a three-dimensional '3D' version of the visual content; and identify an instance of a statistically significant difference with regard to where the first viewer's and the second viewer's gaze is directed between the first ROI data and the second ROI data for at least one frame of the visual content, indicative of an instance of viewing fatigue of the second viewer, wherein: the first ROI data is made up of three-dimensional co-ordinates for the first viewer for each frame of the 2D version of the visual content indicating the first viewer's region of interest based on correlating depth data from a per-frame depth map for pixels in each frame of the visual content with eye tracking data indicating a direction of a line of sight of a gaze of at least one eye of the first viewer; and the second ROI data is made up of three-dimensional co-ordinates for the second viewer of a convergence point for the second viewer based on eye tracking data indicating lines of sight of each eye of a pair of eyes of the second viewer for each frame of the 3D version of the visual content indicating the second viewer's region of interest. compare a first region of interest 'ROI' data associated with a first viewer of a first visual presentation of a two-dimensional '2D' version of visual content to a second ROI data associated with a second viewer of a second visual presentation of a three-dimensional '3D' version of the visual content; and identify an instance of a statistically significant difference with regard to where the first viewer's and the second viewer's gaze is directed between the first ROI data and the second ROI data for at least one frame of the visual content, indicative of an instance of viewing fatigue of the second viewer, wherein: the first ROI data is made up of three-dimensional co-ordinates for the first viewer for each frame of the 2D version of the visual content indicating the first viewer's region of interest based on correlating depth data from a per-frame depth map for pixels in each frame of the visual content with eye tracking data indicating a direction of a line of sight of a gaze of at least one eye of the first viewer; and the second ROI data is made up of three-dimensional co-ordinates for the second viewer of a convergence point for the second viewer based on eye tracking data indicating lines of sight of each eye of a pair of eyes of the second viewer for each frame of the 3D version of the visual content indicating the second viewer's region of interest. the first ROI data is made up of three-dimensional co-ordinates for the first viewer for each frame of the 2D version of the visual content indicating the first viewer's region of interest based on correlating depth data from a per-frame depth map for pixels in each frame of the visual content with eye tracking data indicating a direction of a line of sight of a gaze of at least one eye of the first viewer; and the second ROI data is made up of three-dimensional co-ordinates for the second viewer of a convergence point for the second viewer based on eye tracking data indicating lines of sight of each eye of a pair of eyes of the second viewer for each frame of the 3D version of the visual content indicating the second viewer's region of interest.