Category: Blog

Dr Tom McClelland – The Architecture of Consciousness Project – University of Manchester

There are some prop­er­ties you can see and some you can­not. When you look at the pic­ture below, for instance, what do you see? I see col­ours such as the yel­low­ness of the banana, I see shapes such as the banana’s curve, I see spa­tial rela­tions such as the banana’s prox­im­ity to the man’s head and I see tex­tures such as the smooth­ness of the man’s neck­tie. There are oth­er prop­er­ties I don’t see. I don’t see the banana’s prop­erty of being a source of potassi­um or its prop­erty of cost­ing 28p. And I don’t see the man’s prop­erty of being a mem­ber of the Labour Party or his prop­erty of being an eld­er broth­er. On the basis of what I see I might judge that the things I’m look­ing at have these prop­er­ties, but that’s not the same as actu­ally see­ing those prop­er­ties. After all, prop­er­ties like ‘being a source of potassi­um’ just aren’t the kind of thing that one could see.

The examples I’ve men­tioned shouldn’t be too con­ten­tious, but there are many kinds of prop­erty that do cause con­tro­versy. For instance, can you see what kind of object some­thing is, such as see­ing the smal­ler object as a banana and the lar­ger object as a man? Can you see caus­al prop­er­ties such as the banana being sup­por­ted by the hand, or afford­ances such as the banana being edible? Can you see aes­thet­ic prop­er­ties such as the banana’s beauty, or mor­al prop­er­ties such as the man’s vir­tue? Can you see the iden­tity of objects, like see­ing the man as David Miliband?

There is a great deal of debate in philo­sophy about these con­ten­tious cases, and the dis­putants fall into two camps. The first camp are con­ser­vat­ives, and they say that our visu­al exper­i­ences are lim­ited to the basic kinds of prop­erty I first lis­ted: col­ours, shapes, spa­tial rela­tions and tex­tures (e.g. Prinz 2012; Brogaard 2010). These con­ser­vat­ives shouldn’t be con­fused with polit­ic­al Conservatives, but like polit­ic­al Conservatives they are big on aus­ter­ity – they take an aus­tere view of visu­al exper­i­ence that excludes all the con­ten­tious prop­er­ties. The second camp are lib­er­als, and this camp adopts a much more inclus­ive view of per­cep­tion (e.g. Siegel 2012; Bayne 2009). They hold that at least some of the con­ten­tious prop­er­ties can be visu­ally exper­i­enced. Again, this kind of lib­er­al shouldn’t be con­fused with polit­ic­al Liberals, but like polit­ic­al Liberals they are end­lessly arguing among them­selves about just how lib­er­al they should be — the prop­erty of being a man is surely per­mit­ted as a vis­ible prop­erty, but might per­mit­ting the prop­erty of being vir­tu­ous be a step too far?

Now, which camp are you in? The ques­tions I’ve been ask­ing are about what it’s like for you to have the visu­al exper­i­ence you have when you look at the photo above. Conservatives would offer an aus­tere descrip­tion of your exper­i­ence involving only the lim­ited range of prop­er­ties that they coun­ten­ance. If you think that such a descrip­tion fully cap­tures what your visu­al exper­i­ence is like, then you’re a con­ser­vat­ive (don’t worry — that doesn’t come with any polit­ic­al com­mit­ments). If, on the oth­er hand, you think there’s more to your visu­al exper­i­ence than is cap­tured by the aus­tere descrip­tion, then you’re some kind of lib­er­al, and will have to reflect care­fully on just how wide the range of prop­er­ties you can see is.

I’m a lib­er­al, but I’m think­ing care­fully about just how lib­er­al we should be. Specifically, I’m inter­ested in wheth­er we can see a spe­cial cat­egory of prop­erty called ‘scene cat­egor­ies’. When we open our eyes we don’t just see objects – we also see the wider envir­on­ments in which those objects are embed­ded. The philo­sophy of per­cep­tion tends to focus on our per­cep­tion of objects — there is end­less dis­cus­sion of wheth­er we can see an object as a pine tree, for instance, but no real dis­cus­sion of wheth­er we can see a scene as a forest (e.g. Siegel 2012). I think this is an over­sight and that we should ask ourselves wheth­er we can per­ceive scene cat­egor­ies such as being a forest, being a beach, being a field, being a street, or being a car­park.

Consider the image above. Besides see­ing the vari­ous shapes, col­ours, spa­tial rela­tions and tex­tures in this image do you also see the scene as a forest? Is the scene’s prop­erty of being a forest part of your visu­al exper­i­ence? Conservatives would say that it is not, and would deny that any such scene cat­egory can be per­ceived. They would accept, of course, that we recog­nise the scene as a forest — they would just deny that this recog­ni­tion is per­cep­tu­al. On their view, we see cer­tain pat­terns of col­our and shape and then judge that the scene is a forest. However, I think that a com­bin­a­tion of empir­ic­al and philo­soph­ic­al con­sid­er­a­tions cast doubt on this con­ser­vat­ive view. There are good reas­ons to adopt a lib­er­al view that acknow­ledges we can see scenes as forests or as beaches in much the same way as we can see objects as green or as tall. Conservatives will need some con­vin­cing that we visu­ally exper­i­ence scene cat­egor­ies, and you might need some con­vin­cing too. My case for this has two steps: the first step con­cerns the ‘visu­al’ bit of ‘visu­al exper­i­ence’ and the second step con­cerns the ‘exper­i­ence’.

If con­ser­vat­ives deny that we per­ceive scene cat­egor­ies, they have to say that we recog­nise scene cat­egor­ies through some kind of post-per­cep­tu­al cog­nit­ive pro­cess, such as mak­ing a judge­ment on the basis of what we see. The empir­ic­al data counts against such a view in at least four ways. First, judge­ment is rel­at­ively slow, but our recog­ni­tion of scene cat­egor­ies is incred­ibly fast. Thorpe et al. (1996), for instance, found that when sub­jects were shown images in a scene cat­egor­isa­tion task, their brains showed Event Related Potentials (ERPs) as early as 150 mil­li­seconds after being shown the image. Second, it is gen­er­ally thought that only atten­ded areas of the visu­al field are avail­able to judge­ment, but our recog­ni­tion of scene cat­egor­ies often seems to be inat­tent­ive (see Li et al, 2002). Third, the speed at which we make dis­crim­in­at­ive judge­ments about a stim­u­lus can gen­er­ally be improved if we’re famil­i­ar with the stim­u­lus, or if we form appro­pri­ate expect­a­tions about the stim­u­lus. However, an early study by Biederman et al (1983) sug­gests that famili­ar­ity and expect­a­tion do not speed up our cat­egor­isa­tion of scenes, indic­at­ing that scene cat­egor­isa­tion is an auto­mat­ic per­cep­tu­al pro­cess. Fourth, per­cep­tu­al pro­cesses dis­play a phe­nomen­on known as ‘per­cep­tu­al afteref­fects’ (which you can find more about here). Post-perceptual pro­cesses do not dis­play this effect, but a study by Greene & Oliva (2010) indic­ates that scene cat­egor­isa­tion is sus­cept­ible to aftereffects.

Interpreting this data is not always straight­for­ward, but it cer­tainly looks like scene cat­egor­ies can be recog­nised per­cep­tu­ally, not just through post-perceptual judge­ments. But I’m not home free yet. It’s one thing to per­cep­tu­ally pro­cess a prop­erty but quite anoth­er to per­cep­tu­ally exper­i­ence it. Since I claim that we per­cep­tu­ally exper­i­ence scene prop­er­ties, I have more work to do. This is where some philo­soph­ic­al con­sid­er­a­tions need to be intro­duced to sup­ple­ment the empir­ic­al data. Liberals use some­thing called ‘con­trast cases’ to show that our visu­al exper­i­ence is more rich than con­ser­vat­ives think. Contrast cases are pairs of visu­al exper­i­ences that dif­fer from each oth­er in ways that con­ser­vat­ives are unable to account for. Such cases drive the fol­low­ing argu­ment against conservatives:

1. The two exper­i­ences are alike with respect to all conservative-permitted prop­er­ties i.e. they rep­res­ent all the same col­ours, shapes, spa­tial rela­tions and textures.
2. The two exper­i­ences are nev­er­the­less dif­fer­ent i.e. what it’s like to under­go the first visu­al exper­i­ence is dif­fer­ent to what it’s like to under­go the second.
3. Therefore the two exper­i­ences must dif­fer with respect to prop­er­ties not per­mit­ted by conservatives.

Here is a clas­sic example used by liberals:

To begin, this image looks to most people like a mean­ing­less jumble of black and white patches. But if you look closely you can recog­nise it as a pic­ture of a cow (the face is on the left and is look­ing towards you). This rev­el­a­tion changes what your visu­al exper­i­ence is like, but the con­ser­vat­ive can’t explain this change because there is no dif­fer­ence in the col­ours, shapes (etc.) that you see. Surely what changes is that you start to see the image as a cow? Conservatives deny that we see this kind of prop­erty, but this con­trast case sug­gests they are wrong. Perhaps a sim­il­ar example can be found in which we come to visu­ally exper­i­ence a scene cat­egory. Consider the fol­low­ing image:

Again, you might start by see­ing mean­ing­less patches of black and white but then come to recog­nise that this scene is a water­fall. To make sense of this change, it seems we must say that we visu­ally exper­i­ence the prop­erty of being a water­fall. Here’s anoth­er kind of example often used by liberals:

You might first recog­nise this image as a rab­bit then recog­nise it as a duck. Your visu­al exper­i­ence rep­res­ents the same conservative-permitted prop­er­ties in both cases, so the change must involve some more con­ten­tious prop­erty, such as visu­ally exper­i­en­cing the image first as a rab­bit then as a duck. Again, we might be able to find a counter-part to this example involving scene cat­egor­ies. Consider the fol­low­ing image:

These sand dunes look a lot like waves, and you might be able to switch between visu­ally exper­i­en­cing this scene as a desert then visu­ally exper­i­en­cing it as a sea. If so, this would again be a case in which we see scene categories.

Although these brief argu­ments are far from con­clus­ive, they offer a taste of the lar­ger case I hope to make in favour of the vis­ib­il­ity of scene cat­egor­ies. Ultimately though, there’s only one way to decide where you stand on these issues, and that is to ask your­self what you can see!

 

REFERENCES

 

Bayne, T. (2009). Perception and the Reach of Phenomenal Content. Philosophical Quarterly, 59(236), 385–404.

Biederman, I., Teitelbaum, R. C., & Mezzanotte, R. (1983). Scene Perception: A Failure to Find a Benefit From Prior Expectancy or Familiarity. Journal of Experimental Psychology, 9(3), 411–429.

Brogaard, B. (2013). Do we per­ceive nat­ur­al kind prop­er­ties? Philosophical Studies, 162 (1), 35–42.

Greene, M. R., & Oliva, A. (2010). High-Level Aftereffects to Global Scene Properties. Journal of Experimental Psychology, 36(6), 1430–1442.

Li, F. F., VanRullen, R., Koch, C., & Perona, P. (2002). Scene cat­egor­iz­a­tion in the near absence of atten­tion. Proceedings of the National Academy of Sciences of the United States, 99(14), 9596–9601.

Prinz, J. (2012). The Conscious Brain: How Attention Engenders Experience. Oxford: OUP.

Siegel, S. (2012). The Content of Visual Experience. Oxford: OUP.

Thorpe, S., Fize, D., & Marlot, C. (1996). Speed of Processing in the Human Visual System. Nature, 381, 520–523.