A system comprising: an input arranged to receive attention tracking data from attention tracking hardware that is co-located with a display device, wherein the display device is a persistent display device that requires more power to update the display compared to displaying a static image; a processor; and a memory (130, 430) arranged to store pending display change requests, attention tracking software and a display change control module, wherein a display change request is an item of updated information for updating rendering of an application's graphical user interface, the attention tracking software arranged to determine a user's gaze direction using the attention tracking data, and the display change control module comprising device-executable instructions, which when executed, cause the processor to: receive display change requests from a plurality of applications; store the display change requests in the memory; grouping one or more display change requests that can be rendered at the same time based on parameters associated with each display change request, wherein the parameters relate to when and in what way the display change request is to be displayed and include a time window parameter indicating a time window in which a change defined in the display change request must be rendered; select a display change request from those stored in the memory based on the user's gaze direction and parameters associated with each display change request; and cause the change defined by the selected display change request and one or more other changes defined by one or more other display change requests in a same group as the selected display change request to be rendered in a graphical user interface, GUI, on the display device, wherein the change defined by the selected display change request and one or more other changes defined by the one or more other display change requests in the same group as the selected display change request are rendered at the same time. an input arranged to receive attention tracking data from attention tracking hardware that is co-located with a display device, wherein the display device is a persistent display device that requires more power to update the display compared to displaying a static image; a processor; and a memory (130, 430) arranged to store pending display change requests, attention tracking software and a display change control module, wherein a display change request is an item of updated information for updating rendering of an application's graphical user interface, the attention tracking software arranged to determine a user's gaze direction using the attention tracking data, and the display change control module comprising device-executable instructions, which when executed, cause the processor to: receive display change requests from a plurality of applications; store the display change requests in the memory; grouping one or more display change requests that can be rendered at the same time based on parameters associated with each display change request, wherein the parameters relate to when and in what way the display change request is to be displayed and include a time window parameter indicating a time window in which a change defined in the display change request must be rendered; select a display change request from those stored in the memory based on the user's gaze direction and parameters associated with each display change request; and cause the change defined by the selected display change request and one or more other changes defined by one or more other display change requests in a same group as the selected display change request to be rendered in a graphical user interface, GUI, on the display device, wherein the change defined by the selected display change request and one or more other changes defined by the one or more other display change requests in the same group as the selected display change request are rendered at the same time. receive display change requests from a plurality of applications; store the display change requests in the memory; grouping one or more display change requests that can be rendered at the same time based on parameters associated with each display change request, wherein the parameters relate to when and in what way the display change request is to be displayed and include a time window parameter indicating a time window in which a change defined in the display change request must be rendered; select a display change request from those stored in the memory based on the user's gaze direction and parameters associated with each display change request; and cause the change defined by the selected display change request and one or more other changes defined by one or more other display change requests in a same group as the selected display change request to be rendered in a graphical user interface, GUI, on the display device, wherein the change defined by the selected display change request and one or more other changes defined by the one or more other display change requests in the same group as the selected display change request are rendered at the same time.