An information processing device comprising: a display, a display control unit configured to display on the display a target list including list items, a detection unit configured to detect a user operation; the information processing device being characterized in that the display control unit is further configured to: a) display on the display at least one sub-list including list items, wherein the at least one sub-list is displayed adjacent to the target list and the list items of the target list are displayed in a size that is larger than a size of the list items of the at least one sub-list; and in response to a detected user operation indicating coupling of lists, couple the at least one sub-list to the target list by widening for every two neighbouring list items of the target list a space between the respectively neighbouring list items, gradually moving each list item of the at least one sub-list to a corresponding one of the widened spaces, and adjusting the size of the moved list items of the at least one sub-list to the size of the list items of the target list so that the respective sizes become uniform, and/or b) in response to a detected user operation indicating separation of lists, separate a predetermined number of list items from the target list and arrange the separated list items in a new sub-list, wherein the list items to be separated from the target list gradually become smaller in size and move away from the target list to a corresponding display position in the sub-list adjacent to the target list, and spaces in the target list caused by moving the separated list items to the sub-list are narrowed by moving the respectively neighbouring list items of the separated list items in the target list closer to each other. a display, a display control unit configured to display on the display a target list including list items, a detection unit configured to detect a user operation; the information processing device being characterized in that the display control unit is further configured to: a) display on the display at least one sub-list including list items, wherein the at least one sub-list is displayed adjacent to the target list and the list items of the target list are displayed in a size that is larger than a size of the list items of the at least one sub-list; and in response to a detected user operation indicating coupling of lists, couple the at least one sub-list to the target list by widening for every two neighbouring list items of the target list a space between the respectively neighbouring list items, gradually moving each list item of the at least one sub-list to a corresponding one of the widened spaces, and adjusting the size of the moved list items of the at least one sub-list to the size of the list items of the target list so that the respective sizes become uniform, and/or b) in response to a detected user operation indicating separation of lists, separate a predetermined number of list items from the target list and arrange the separated list items in a new sub-list, wherein the list items to be separated from the target list gradually become smaller in size and move away from the target list to a corresponding display position in the sub-list adjacent to the target list, and spaces in the target list caused by moving the separated list items to the sub-list are narrowed by moving the respectively neighbouring list items of the separated list items in the target list closer to each other. a) display on the display at least one sub-list including list items, wherein the at least one sub-list is displayed adjacent to the target list and the list items of the target list are displayed in a size that is larger than a size of the list items of the at least one sub-list; and in response to a detected user operation indicating coupling of lists, couple the at least one sub-list to the target list by widening for every two neighbouring list items of the target list a space between the respectively neighbouring list items, gradually moving each list item of the at least one sub-list to a corresponding one of the widened spaces, and adjusting the size of the moved list items of the at least one sub-list to the size of the list items of the target list so that the respective sizes become uniform, and/or b) in response to a detected user operation indicating separation of lists, separate a predetermined number of list items from the target list and arrange the separated list items in a new sub-list, wherein the list items to be separated from the target list gradually become smaller in size and move away from the target list to a corresponding display position in the sub-list adjacent to the target list, and spaces in the target list caused by moving the separated list items to the sub-list are narrowed by moving the respectively neighbouring list items of the separated list items in the target list closer to each other.