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…
Richard Brown 
Hi Richard,
A question about the article. You say “Nonetheless both the unchanged number and the changed number showed a priming effect.”.
I’m not sure I get it. Does it mean that if number X was changed with Y, both X and Y showed priming effect, or something else?
Yes that’s right. Both numbers showed priming effects (it turns out it is whole rows of numbers that are replaced, but the point is the same), unless the change was detected in which case it was only the changed number that showed priming. It seems to me that this is hard to explain on a view like yours…
Hey, thanks for adding me to your blog roll.
I actually have conducted some research in a related area-the attentional blink. Last year I worked with Thomas Ghirardelli (Goucher College) looking at practice effects and specifically whether practice resulted in an elimination of the AB.
In any event, I just wanted to let you know that my blog address has changed. Language Games is now located at the following address:
http://theory.typepad.com/language_games/
Please update your blog roll 😉
I’ll add your site right now to mine as well, and I’m sorry for the delay in thanking you. Great blog.
Hi Richard,
I agree that HOT has pretty simple explanation for what is happening in those cases.
1. But , I’m little puzzled about possibility of somebody being ‘conscious of X’ or ‘seeing X’, where X is something which the person doesn’t notice. Wouldn’t that go against the meaning of ‘conscious of’ and ‘see’? E.g. we don’t say ‘I saw the hidden object’ when looking at a puzzle, just because we know that the puzzle contains the hidden object. We will use ‘see’ or ‘conscious of’ just when we actually notice it.
2.But maybe this doesn’t present problem for Dretske’s view though? Can’t he say that the thing-awareness can be a reason for priming as long this thing-awareness is present in the short-term memory? That because even we are not aware of the facts, this thing-awareness is compatible with there being some facts, and incompatible with others.
DPrice, thanks for the compliment! I have updated the link…
Hi Tanasije,
Re 2- I guess I wasn’t specific enough…what I meant was that this is evidence against Dretske’s argument against higher-order theories from change blindness. He presents change blindness as a problem for higher-order accounts as it looks like an example of a conscious experience that we are not conscious of. But this study shows, I think, that that is wrong. There is no non-question beging reason to think that the part of the picture that we see but do not notice is consciously seen…
Re 1: To be conscious of something is simply to sense it or to think about it. People often use ‘see’ and ‘conscious of’ to mean ‘consciously see’ and ‘consciously conscious of’ but that isn’t a problem for this theoretical account…
[…] Richard Brown, Philosophy Sucks! Priming and Change Blindness […]
As the one who is a mental health major Professor, don’t you think this is an economical tool that is and has been used in marketing and in business. I once had a teacher in high school, Brooklyn Tech complain about the evidentially visibly dwindling size of a muffin. Apparently the muffin used to be a larger size for a dollar but then got smaller over time but the price of the bagel went up a quarter. There seems to be a practical economic benefit to using priming and change blindness. Do you agree or disagree
While I am lite on the philosophical lingo, I can still try to see the pragmatic application to these queries and possible dilemas. Fate was unknid in many ways. One of which was to give me an inquisitive mind but not much in the area of anayltic and mathematical skills. Bear with me please.
Hi CHRISSYSNOW
There is no doubt that findings from psychology are/have been applied in advertising (think about what happened when subliminal advertising first hit the scene)…
[…] have been thinking about this issue and in light of my last post on priming and change blindness where I voiced my suspicion that the results posed a problem for […]
[…] have been around here lately you will have noticed that I have been talking a lot about priming, change blindness and the function of conscious mental states in the higher-order theory. I have been arguing that […]
Dretske has published to other papers on change blindness in addition to the one that was referred to earlier in the blog
Perception without awareness
(http://www.nyu.edu/gsas/dept/philo/courses/representation/papers/Dretske.pdf)
WHAT CHANGE BLINDNESS TEACHES ABOUT
CONSCIOUSNESS∗ (Philosophical Perspectives, 21, Philosophy of Mind, 2007)
I was wondering whether you guys think that the cases Dretske discusses is also comparable with the flicker-paradigm and change blindness where there is a slow gradual change?
In the cases Dretske discusses we always have plenty of time to inspect the scene before and after the change, making it likely that we were aware of every object even if we were unaware of the change.
But I don’t know whether it is a plausible thing to claim in connection to the flicker paradigm where we here have to get a grip of the visual scene and search for the change simultaneously and perhaps it can even be argued that we do not have awareness of the event of the change in the case with the slow gradual change.
Furthermore, what do you think about debate over the subjective criterion and the objective criterion for conscious experiences and Dretskes attempt in his article (perception without awareness) to say that an experience is conscious if the information is available as a justifying reason for the subject?
Hi Niels thanks for the comment and the questions.
I do think it is fair to say that we are conscious of the stimulus in the flicker design. In order for their to be priming effects there must have been some representation of the stimulus. Why should we expect that this representation is any different from the one that we are conscious of having?
Re your second question it seems to me that if the information is available as a justifying reason fo rthe subject then the subject must be conscious of the information in some suitable way and so this is really to give in to the transitivity principle.
Hi Richard,
in connection to the flicker design and Dretske: I guess, I was thinking about experiments where more real-life stimuli are used. In the Fernandez et al experiment we have a very simple stimulus with few details.
When we are being presented with with a photography full of people etc it strikes me as less plausible that we manage to have every detail in focused view from both before and after the change because we are given only a few hundred milliseconds to inspect the scene, then there is a blank image disrupting our focus…
The significance of this is merely that I think that the cases Dretske discusses are not really paradigmatic for CB studies at all. He always gives the subjects a couple of seconds to inspect a scene and then a couple of seconds to inspect the scene afterwards.
It seems to me that in flicker design where photographs are used, the changes are so large that if you manage to get a focused view of the objects from both before and after the change then you are bound to notice it, thus making it unlikely that you under these circumstances are object aware of the things that make up the change without being fact aware of the difference.
Correspondingly, it seems that in the design with the slow gradual change that you can only be object aware of the event of the change if you focus on the same place long a enough for the change to unfold (given the slow rate of the event).
Dretske likes to think that CB is a matter of difference blindness because change conceived as an event is concealed – but in the case with the slow gradual change the event is not concealed at all; it only requires that your eyes are focused on the same place for a while.
I don’t think that this is merely a matter of that we don’t notice the event; we don’t see it if our eyes are busy inspecting the whole scene and not focused on the same spot long enough for the transformation to occur.
Let me know what you think – I am a philosophy student and really have no insight into matters of cognitive psychology.