23. A non-transitory, computer-readable medium storing computer executable instructions that, when executed by one or more computing devices, configure the one or more computing devices to perform operations comprising: from an item of original content comprising a plurality of original objects, selecting an original object, the selected original object comprising original attributes; selecting a replacement object from a source other than the item of original content; replacing, in the item of original content, the original attributes of the selected original object with attributes of the replacement object to form an item of modified content; determining a coherence value for the item of modified content, wherein the coherence value is based at least in part on a number of times that two or more words included in the item of modified content appear together in a plurality of items of original content; and based at least in part on a determination that the coherence value does not satisfy a threshold value, replacing, in the item of modified content, at least one attribute of the selected replacement object with at least one of: a different attribute of the selected replacement object or an attribute of a different replacement object.
23. A non-transitory, computer-readable medium storing computer executable instructions that, when executed by one or more computing devices, configure the one or more computing devices to perform operations comprising: from an item of original content comprising a plurality of original objects, selecting an original object, the selected original object comprising original attributes; selecting a replacement object from a source other than the item of original content; replacing, in the item of original content, the original attributes of the selected original object with attributes of the replacement object to form an item of modified content; determining a coherence value for the item of modified content, wherein the coherence value is based at least in part on a number of times that two or more words included in the item of modified content appear together in a plurality of items of original content; and based at least in part on a determination that the coherence value does not satisfy a threshold value, replacing, in the item of modified content, at least one attribute of the selected replacement object with at least one of: a different attribute of the selected replacement object or an attribute of a different replacement object. 25. The non-transitory, computer-readable medium of claim 23 , wherein the operations further comprise obtaining at least one user profile.