References to these essays must cite them explicitly as unpublished manuscripts. Copies may be circulated if this statement is included on each copy. There is, of course, a class of experiences that does not elicit overt behavior.
Afterimages are an example.
It would be very difficult to determine whether animals have afterimages. If they do, it is likely that they would pay no attention to them. There is another class of experiences which are not subjective or private, are similar to perceptions, but are nevertheless false. Such virtual objects are presumably falsely perceived by all seeing observers, animal or human. Pictures are another example.