A couple of weeks ago I attended Ian Phillips’ CogSci talk at CUNY. Things have been hectic but I wanted to get down a couple of notes before I forget.

He began by reviewing change blindness and inattentional blindness. In both of these phenomena subjects sometimes fail to recognize (or report) changes that occur right in front of their faces. These cases can be interpreted in two distinct ways. On one interpretation one is conscious only of what what is able to report on, or attend to. So if there is a doorway in the background that is flicking in and out of existence as one searches the two pictures looking for a difference and when one is asked one says that they see no difference between the two pictures one does not consciously experience the door way or its absence. This is often dubbed the ‘sparse’ view and it is interpreted as the claim that conscious perception contains a lot less detail in it than we naively assume.

Fred Dretske was a well known defender of a view on which distinguishes two components of seeing. There is what he called ‘epistemic seeing’ which, when a subject sees that p, “ascribes visually based knowledge (and so a belief) to [the subject]”. This was opposed to ‘simple seeing’ which “requires no knowledge or belief about the object seen” (all quoted material is from Phillips’ handout). This ‘simple seeing’ is phenomenally conscious but the subject fails to know that they have that conscious experience.

This debate is well known and been around for a while. In the form I am familiar with it it is a debate between first-order and higher-order theories of consciousness. If one is able to have a phenomenally conscious experience in the absence of any kind of belief about that state then the higher-order thought theory on which consciousness requires a kind of higher-order cognitive state about the first-order state for conscious perception to occur, is false. The response developed by Rosenthal, and that I find pretty plausible, is that in change blindness cases the subject may be consciously experiencing the changing element but not conceptualize it as the thing which is changing. This, to me, is just a higher-order version of the kinds of claims that Dretske is making, which is to say that this is not a ‘sparse’ view. Conscious perception can be as rich and detailed as one likes and this does not require ‘simple seeing’. Of course, the higher-order view is also compatible with the claim that conscious experience is sparse but that is another story.

At any rate, Phillips was not concerned with this debate. He was more concerned with the arguments that Dretske gave for simple seeing. He went through three of Dretske’s arguments and argued that each one had an easy rejoinder from the sparse camp (or the higher-order camp). The first he called ‘conditions’ and involved the claim that when someone looks at a (say) picture for 3-5 minutes scanning every detail to see if there is any difference between the two, we would ordinarily say that they have seen everything in the two pictures. I mean, they were looking right at it and their eyes are not defective! The problem with this line of argument is that it does not rule out the claim that they unconsciously saw the objects in question. The next argument, from blocking, meets the same objection. Dretske claims that if you are looking for your friend and no-one  is standing in front of them blocking them from your sight, then we can say that you did see your friend even if you deny it. The third argument involved that when searching the crowd for your friend you did saw no-one was naked. But this meets a similar objection to the previous two arguments. One could easily not have (consciously) seen one’s friend and just inferred that since you didn’t see anyone naked your friend was naked as well.

Phillips then when on to offer a different way of interpreting simple seeing based on signal detection theory. The basic intuition for simple seeing, as Phillips sees it, lies in the idea that the visual system delivers information to us and then there is what we do with the information. The basic metaphor was a letter being delivered. The delivery of the letter (the placing of it into the mailbox) is one thing, you getting the letter and understanding the contents, is another. Simple seeing can then be thought of as the informative part and the cognitive noticing, attending, higher-order thought, etc, can be thought of as a second independent stage. Signal detection theory, on his view, offers a way to capture this distinction.

Signal detection theory starts with treating the subject as an information channel. They then go on to quantify this, usually by having the subject perform a yes/no task and then looking at how many times they got it right (hits) versus how many times the got it wrong (false alarms). False alarms, specifically, involve the subject saying the see something but being wrong about it, because there was no visual stimulus. This is distinguished from ‘misses’ where there was a target but the subject did not report it. The ‘sensitivity to the world’ is called d’, pronounced “d prime”. On top of this there is another value which is computed called ‘c’. c, for criterion, is thought of as measuring a bias in the subjects response and is typically computed from the average of hits versus false alarms. One can think of the criterion as giving you a sense of how ‘liberal’ or ‘conservative’ the subjects’ response is. If they will say they saw something all the time then the seeming have a very liberal criterion for determine whether they saw something (that is to say they are biased towards saying ‘yes I saw it’ and is presumably mistaking noise for a signal). If they never say the say it then they are very conservative (they are biased towards saying ‘no I didn’t see it). This gives us a sense of how much of the noise in the system the subject treats as actually carrying information.

The suggestion made by Phillips was that this distinction could be used to save Dretske’s view if one took d’ to track simple seeing and c to track they subjects knowledge. He then went on to talk about empirical cases. The first involved memory across saccades and came from Hollingworth and Henderson, Accurate Visual Memory for Previously Attended Objects in Natural Scenes, the second f rom Mitroff and Levin Nothing Compares 2 Views: Change Blindness can occur despite preserved access to the changed information, and the third Ward and Scholl Inattentional blindness reflects limitation on perception, not memory. Each of these can be taken to suggest that there is “evidence of significant underlying sensitivity in [change blindness] and [inattentional blindness],”.

He concluded by talking about blindsight as a possible objection. Dretske wanted to avoid treating blindsight as a case of simple seeing (that is of there being phenomenal consciousness that the subject was unaware (in any cognitive sense) of having). Dretske proposed that what was missing was the availability of the relevant information to act as a justifying reason for their actions. He then went on to suggest various responses to this line of argument. Perhaps blindsight subjects who do not act on the relevant information (say by not grabbing the glass of water in the area of their scotoma) are having the relevant visual experience but are simply unwilling to move (how would we distinguish this from their not having the relevant visual experience)? Perhaps blindsight patients can be thought of as adjusting their criterion and so as choosing the interval with the strongest response and if so this can be thought of as reason responsive. Finally, perhaps, even though they are guessing, they really can be thought of as knowing that the stimulus is there?

In discussion afterwards I asked whether he though this line of argument was susceptible o the same criticism he had leveled against Dretske’s original arguments. One could interpret d’ as tracking conscious visual processing that the subject doesn’t know about, or one could interpret it as tracking the amount of information represented by the subjects mental states independently of what the subject was consciously experiencing (at leas to some extent). So, one might think, the d’ is good so the subject represents information about the stimulus that is able to guide its behavior, but that may be going on while the subject is conscious of some of it but not all of it, or different aspects of it, etc. So there is no real reason to think of d’ as tracking simple (i.e. unconceptualized, unnoticed, uncategorized, etc) content that is conscious as opposed to non-conscious. He responded that he did not think that this constituted an argument. Rather he was trying to offer a model that captured what he took to be Dretske’s basic intuition, which was that there was the information represented by the visual system, which was conscious, and then there was the way that we were aware of that information. This view was sometimes cast as unscientific and he thought of the signal detection material as proving a framework that, if interpreted in the way he suggested, could capture, and thus make scientifically acceptable, something like what Dretske (and other first-order theorists) want.

There was a lot of good discussion, a lot of which I don’t remember, but I do remember Ned Block asking about Phillips’ response to cases like the famous Dretske example of a wall, painted a certain color, having a piece of wallpaper in one spot. The little square of wallpaper has been painted and so is the same color as the wall. If one is looking at the wall and doesn’t see that there is a piece of wallpaper there, does one see (in the simple seeing kind of way) the wallpaper? Phillips seemed to be saying we did (but didn’t know it) and Block asked whether it wasn’t the case that when we se something we represent it visually and Phillips responded by saying that on the kind of view he was suggesting that wasn’t the case. Block didn’t follow up and didn’t come out after so I didn’t get the chance to follow up on that interesting change.

Afterwards I pressed him on the issue I raised. I wondered what he thought about the kinds of cases, discussed by Hakwan Lau (and myself) where the d’ is matched but subjects give differing answers to questions like ‘how confident are you that you saw it?’ or ‘rate the visibility of the thing seen’. In those cases we have, due to matched d’, the same information content (worldly sensitivity) and yet one subject says they are guessing while the other says they are confident they saw it (or rates its visibility lower while the other rates it higher (so as more visible)). Taking this seriously seems to suggest that there is a difference in what it is like for these subjects (a difference in phenomenal consciousness) while there is no difference in what they represent about the world (so at the first-order level). The difference in what it is like for them seems to track the way in which they are aware of the first-order information (as tracked by their visibility/confidence ratings). If so then this suggests that d’ doesn’t track phenomenal consciousness. Phillips responded by suggesting that there may be a way to talk about simple seeing involving differences in what it is like for the subject but didn’t elaborate.

I still am not sure how he responds to the argument Hakwan and I have given. If there is differing conscious experience with the same first-order states each in each case then the difference in conscious experience can only be captured (or is best captured) by some kind of difference in our (higher-order) awareness of those first-order states.

In addition, now that I have thought about it a bit, I wonder how he would respond to Hakwan’s argument (more stemming from his own version of higher-order thought theory) that the setting of the criterion in Phillips’ appeal to it in blindsight cases, depends on a higher-order process and so amounts to a cognitive state having a constitutive role in determining how the first-order state is experienced. This suggests that an ‘austere’ notion of simple seeing where there is no cognitive states involved in phenomenal consciousness is harder to find than Phillips originally thought.