Change blindness is one of those surprising things that cognitive science has revealed about the nature of conscious experience. It turns out th at there can be rather large changes in the visual scene a person is looking at and that most people will completely miss them! I am not talking about small changes but rather very large changes right in front of the faces that are actively looking for changes (for some nice examples see this link). Once one sees the difference it is so obvious that ones attentionis drawn to it every time, but for a while it really looks as though there is no difference between the two pictures.

Any theory of consciousness should be able to account for this phenomena. Fred Dretske, in his well known paper “Change Blindness” (requires a password), gives the following account of what is going on in instances of change blindness. He distinguishes between thing-awareness and fact-awareness. Thing awareness is our being conscious of some physical thing in the world. Examples include seeing blue, hearing music, etc. Fact-awareness is our being conscious of some fact. From the way that Dretske talks about fact-awareness it sounds like it consists in having the appropriate belief, but to be honest I am not sure exactly what his view is on this (especially given that he seems doubtful as to whether or not having a belief makes one conscious of anything in the first place).

Given these distinctions he then gives his account of change blindnessas follows. When one is looking at the two pictures one is thing aware of them, where this means that one sees the two pictures. But one is not fact-aware that there is a difference between them. This view is contrasted with what he calls the ‘object view’ which claims that one sees both of the pictures and the difference between them but does not notice that one is seeing the difference.

The object view is pretty much what the higher-order thought theory of consciousness predicts. On that kind of theory one is in a first-order visual state that represents both pictures but one is also in a higher-order state that (mis)-represents the first-order states as not differing. That is, one is conscious of the difference between the two pictures but one is not conscious of it AS the difference. Dretske takes change blindness to be a counter-example to the transitivity principle as he thinks that what we have is a case of a conscious experience (the experience of the thing that is different as between the two pictures) but that we are not conscious of having.

So which of these two accounts is right?  This recent article on change blindness and priming seems to me to offer evidence against Dretske’s account (not to mention evidence against ‘naive realist’ and anto-representationalist views generally). In the experiments subjects were presented with two alternating pictures of numbers arranged in rows and columns. In the second picture one of the numbers was changed and subjects failed to notice this change. Nonetheless both the unchanged number and the changed number showed a priming effect.  What this suggests is that both pictures are represented by the visual system even though both are not consciously experienced. When one looks at the two pictures they look the same! One can spend minutes examining those pictures convinced that there really isn’t any difference between them and the whole thing must be a joke. But it isn’t. There is a difference and it is a strikingly large difference. So even though there is nothing that it is like for you to be conscious of the thing that makes the difference between the two pictures, you are conscious of it; just not as the difference. How is this going to be explained on a first-order view like Dretske’s

The other interesting thing about this study was that they found that when the change is detected, that is when one sees the two pictures and notices that the second one is different, then it is only the second picture’s information that does any priming. They suggest that the first representation is still there but is inhibited…this might pose a problem for Rosenthal’s argument that conscious states do not have any fucntion…but I will leave that for another time…

Via Tanasije I found Michael Tye’s paper The Puzzle of True Blue where he considers the problem posed by the well known fact that people’s color discriminations vary widely from person to person. So you and I could both be looking at some particular color and I might think that it is true blue, not at all greenish while you might think that it is not true blue (a little bit greeninsh). Tye considers some standard answers to the puzzle before presenting his own. I will skip the standard ones and go straight to Tye’s.

 He suggests that the visual system evolved to respond to the general color categories and that the particular shade of the general color is unimportant and so a sort of ‘”guess” on the part of the visual system. But there is yet another alternative account. It may be the case that you and I have the same first order mental states of the determinate shade and different higher-order representations of that first-order state. The same sort of story could be told…In order to determine which is right we would have to present the colors to the subjects subliminally, record the brain activity, present the colors to the subject superliminally, record the brain activity and note the differences… 

I think that the Higher-Order theory of consciousness is a well worked out naturalistic theory of consciousness that has a decent shot at actually being true. This is not to say that I actually think it is true, or which version of it is, but it seems to me that it has the advantage over every other kind of theory out there. The best part about higher-order theories, though, is that they are worked out in enough detail so that we can begin to evalutate it for empirical adequacy. I have previously argued that there is empirical evidence that points in this way (On Hallucinating Pain, HOT Block, Swimming Vegetables? Fish, Pain, and Consciousness)

Via David Rosenthal my attention was brought to a recent NY Times article, Go Ahead, Rationalize. Monkeys Do It, Too where they discuss research that suggests that rationalizing ones choices is an unconscious, automatic process. The research on animals is fascinating, but perhaps the most convincing is the data on amnesiacs. These people showed the same rationalizing patterns as control subjects even though they did not remember choosing the object (which they now rated higher). This suggests that there are unconscious mental states at play in the amnesiac’s rationalization process. Furthermore, given that people tend to confabulate when asked why they made the rankings that they did this suggests that we are conscious of the process in a way that differs from the actual nature of the (then) unconscious mental state. How else could this be explained if not by a theory of consciousness that depends on the transitivity principle?