Every now and then the issue of mental images takes me in. In general it is an understudied and underdetermined conceptual schema. I get the feeling that it is just terminological and conceptual confusion. I will grant that it is one's own mental image, but we can still ask certain questions that clear the air. Here are the pointed questions that takes care of some confusion, but they are often not asked or illucidated within such discussions:
- Are your conjured mental images as robust as real life images? If you create a mental image of an apple, is it as detailed and vivid as looking at an apple on the table? (I find most people deny this when pressed.)
- What is the relationship between dream images and mental images? Are your consciously created mental images as strong as dream images?
- Do your dream images seem as real as everyday real images?
I find in these discussions that people who claim they have mental images usually leave it baldly stated (“Yes, I have mental imagery”) and do not state what exactly they are experiencing. Often, if such people are pressed, they will allow that such images are not as vivid as dream images, or some people will say they do not have dream images as vivid as everyday life.
My general taxonomy here encourages me to say that all perception is mental imagery. When you look at an apple on the table, you have a mental image of that apple as mediated through sensory content. In a dream you (or I at least) have mental images of an apple, seemingly the same as if you are looking at it in real life. If in waking thought I try to create a mental image of an apple, I create nothing that is like the real life image or dream image of an apple.
I can accept that we need image-like or representational talk for much of our brain processing (see Damasio, for instance). My concentrating on a virtual apple allows me to do all sorts of things. It can instigate knowledge about apples, or instigate sensations of hunger and other emotions. I accept that my trying to image an apple is using and reproducing some underlying processes of “apple representing,” that it is using some "image-like" process broadly speaking. There is certainly a street from past immediately perceived imagery, to memory, to present recalling of that past image. When I have a night-dream image of a face I saw today (a perceived image that I had earlier), the image structures in the night-dream is similar as the earlier perception because the “picture” structures are in my head, so to speak. When I close my eyes and try to imagine that face, I am tapping into those “picture” structures and therefore can remember features of such a face or object.
I also admit that there are (at least) two other classes of people. On one hand there are people who have significant processing deficiencies or significant imagery deficiencies. There may be people who do not dream at all. Or there may be people who have significant perceptual and consciousness difficulties, such as blindsight. On the other hand, there may be people who have really strong hallucinations of non-existent phenomena. We should also say that psychostimulants or other conditions create robust images in some unusual way.
But back to the idea that there is a large percentage of people that have robust daydreamed mental imagery and another large (but supposed minority) percentage of people who do not have these mental images. The papers, the wikipedia pages, the Stanford Encyclopedia, and blogs that I have read do not give me confidence that this is anything more than two classes of people who are not expressing their selves in useful and coinciding ways. I will fully admit that fault may lie with me (and others who follow my schematization). That is, it may be that my seeming “darkness” of thought holds imagistic and representational processes that I access when doing my best to think about my house, and that these processes and thoughts may be worthy of the name image. I also agree that in some conceptualized way we may need to refer to what is happening in my brain as an image. That is, there may be brain processes that are relaying information about object structures. If daydreaming processes are giving information that is robust, such that those processes provide rich detail (so that I know or can imagine redecorating every wall of my house, and this provides further information), then it may be prudent to say that almost all individuals, including my self, have mental imagery.
As it stands, if I try to image an apple it is nothing like the vivid image of directly perceiving a real apple, and it is nothing like the vivid image of dreaming of an apple. I question that most people's phenomenology is that different from mine. It seems far more parsimonious to me that most people have rather similar experiences and instead we have had some stupid language and expression problem. If someone has a good study or a good way of explaining what they experience in their mental imagings, I am all ears.
(My latest perusing led me to Eric Schwitzgebel's account, which gels well with the issues I raised above.)