Greetings, everyone!

I am so glad you have decided to take this course with me. I think that we will all learn a lot and have fun in the process. Cognitive science really is the coolest area around, you will see.

Let's see if I can get this to work...

I'm here and looking forward to learning about this stuff biology can't seem to figure out (cognitive science).

McEndree was here.

Hello! I'm not sure who you are, McEndree in Wichita, but I'd like to find out!:) This is Kila from Arkansas, and I'd love it if you mailed me back. Maybe we're related. I used to live in Derby. Adios!

They live in colorado, not to far from Canon City. If you want more info, I'll have to check with them, and get back to you-- you may e-mail me @: ejcook33@aol.com

There are a bunch of McEndree's here in the Ohio Vally. Some, may be from your family tree. Who knows?

Block wants to claim that one way of approaching this problem is by understanding functionalism and how causation works in scientific laws. One version of functionalism (see also the glossary) is the view that mental states or events are to be defined in terms of their connections with inputs, outputs, and other mental states. These connections "mirror" the physical and causal connections among sensory nerve stimulations, neural firing patterns, and motor behavior. But what we also need are for these functional interactions of the mental to be important in explaining behavior, for lots of things mirror or hitchhike other things, and most of them aren't relevant to the explanatory task at hand. So how do we know that the mental properties are required in understanding behavior? A popular answer is that mental properties are found in scientific laws and that is all the legitimation they need.

But that isn't enough yet. First, there are scientific laws that report mere correlations -- and not causes (particularly in the "softer sciences") -- so just being in a law doesn't guarantee you causal relevance. Second, the laws that do capture causal correlations sometimes articulate causal chains that we consider extraneous to the matter at hand (particularly when one effect co-occurs with another), so again being in a laws doesn't guarantee causal relevance. So, to take the bomb example: Block tells a story about a bomb that is triggered by an increase in thermal energy, which co-occurs with an increase in electrical activity. We want to say the thermal energy caused the bomb to explode, even though there is a law-like connection between the electrical activity and the explosion too. How do we know that mental states are analogous to electrical activity in the bomb story? Mental states, events, and properties need to be in the right sort of laws. How do we determine those?

The Macdonalds want to answer this question by leaning on the counterfactual aspect of nomological relations. They point out first that scientific laws are about types of events, classes of similar things (see also the glossary). However, most of the examples that Block discusses concern only token instances of something, a single exemplar of some type (see also the glossary). But if you want to know whether something is genuinely causally relevant, then you have to go beyond the individual instance and see how the case generalizes. If events relevantly similar to the one in question show the same pattern of correlations, then we can infer a genuine causal (and causally important) connection. Returning to the bomb example, they claim that if we generalize over the various instances of bombs, we shall see that bombs are triggered by heat and not by electricity. Hence, we will know that the thermal properties are the relevant ones. Similarly, if we generalize over our behavior, we shall see that what all the triggers for a certain type of behavior have in common is a mental property (or event) or set of properties (or events).

There are two difficulties with this sort of response, one of which Block gives. He notes that we don't really have any scientific laws that concern bombs, or anything else that specific. And our general physical laws wouldn't distinguish between the different possible causings of an explosion. If we created more specific laws, his so-called "apparatus" laws, then we have no reason not to generalize over "thermal bombs" versus "electrical bombs" versus "bombs in general." As long as we are going to be able to get as specific or as general as we want (or as suits our purposes), then we will be able to find any sort of abstraction we desire, some that make mental doodads causally relevant and some that make the same doodads irrelevant.

The second difficulty goes back to Nelson Goodman. He holds that how we "project our predicates" is completely undetermined. The Macdonalds are pretending that how things are generalized and abstracted is already known and accepted, when it in fact isn't. We could generalize over the notion of what a bomb is any way we want; nothing in the world determines how things are supposed to go counterfactually (which is what makes them counterfactuals), so how we devise the counterfactuals is up to us. Whether our generalizations about behavior should include the mind isn't determined by anything in the world.

Block tries a second tact in answering the problem using functionalism. He notes that (if the mind is physical and if it is understood functionally, then) there is no way for some mental state to have a different content (be a different mental state, in other words) and still cause the same behavior. Why? Because the mental state, and its content, are defined in terms of the behavior it is related to. Different outputs = different mental state. Very simple. It has to be relevant because if it were different, then we would get a different output.

But this doesn't answer the epiphenomenal worry (see the glossary for a definition of epiphenomenal). Block views functional properties as second order. That is, they are properties of having other properties. A functional definition of a mental state would be a statement concerning the sorts of interactions this mental state could have, which piggybacks on the physical interactions of the underlying nervous system. In essence then a functional description of the mind is a (covert) conjunction of the sorts of neural or whatever interactions that could underpin the mind. But then what is really causally important are the underpinnings and not the general second order description. That is just a useful shorthand.

But note that this view of functional descriptions and second order properties does away with all or almost all causes. We wouldn't want to say that neural firing patterns caused the behavior either, since that those are really shorthand for describing the chemical interactions that comprise the neural patterns. But causality doesn't bottom out in chemistry either, since that is just shorthand for the quantum interactions that underlie the chemical. But causality isn't at the quantum level either, since there all we get are functional descriptions (just lists of elegant correlations really) with nothing doing the instantiation. So causes don't exist!

I personally find this a bit hinky, though I don't believe that Block does. I prefer to say that causes are at all levels and the real question is determining which are the relevant ones to use in an explanation. I buy the point that it all depends on counterfactual understandings, which is completely underdetermined, but that doesn't bother me (though it makes Block hinky). I think of science as being largely pragmatic anyway. All this is spelled out in a paper of mine, which you can read for emjoyment (if you have an odd sense of fun) or to get a handle on how I think about these matters in greater detail before you come to class.

Valerie

A few questions regarding background for the course:

1. I am curious about about the current status of the mind/body problem. This is the way it was presented to me:

	Functionalism does not really solve the problem,
	Neuroscience has rejected the possibility of an identity theory, and
	Epiphenomenalism is effectively a non-answer.

	Therefore, elimitivism is the only recourse for a materialist.

Now, this is obviously a very Churchlandian argument, but how accurate is it? It certainly smells funny.

2. Along the same vein, I realize that type-type identity does not appear to fit with our understanding of neuroscience, but what about token-token identity? Dretske mentions it in our readings for this week as if it were a viable theory scientifically. Is it?

3. My information regarding the status of scientific findings are a bit outdated. Have there been any recent (the last 4-5 years) findings in cognitive science or neuroscience that are relevant to our philosophical concerns?

I realize that all of these questions have a similar focus. They stem from a curiousity about the scientific side of the issues we are discussing.

This week's reading focuses on psychoanalysis and psychoanalytic explanation. While philosophers and many psychologists generally discount psychoanalytic explanation offhandedly, Hopkins and Johnston argue that the theory can best explain certain aspects of human behavior, particularly wishful thinking and self-deception. Erwin also espouses a view favoring psychoanalytic explanation in his paper on the psychotherapy, though he does express problems with measuring its effectiveness. Psychoanalysis is the theory originating in Freud's work. Generally, psychoanalysis postulates that the mind (brain) can be divided into quasi-independent compartments that each have a significant role in mental activity of a person. With this picture of the mental, psychoanalysis can explain paradoxical aspects of mental life. In particular, the authors concentrate on the difficulties of wishful thinking and self-deception.

Wishful thinking is the idea that if a person strongly desires something to be true, she will come to believe it actually is the case. This is problematic form a monistic view of the mind because the wishful thinker both believes the wishful thought and knows that it is false at the same time. For example, I have a strong desire to get into graduate school and I believe that I will, even though I know that I am severely underqualified. The psychoanalytic explanation of my seemingly contradictory beliefs is that one part of my mind, call it the subconscious, contains the rational belief that I am underqualified for grad school, while a different part of my mind, call it the conscious, both strongly desires that I get in and holds the belief that I will. A third part of the mind would act as a mediator, assigning which beliefs and desires will appear in each of the other compartments (the conscious and subconscious). By this triumvirate, the psychoanalyst can explain the paradox of having contradictory beliefs by separating them within the mind.

The case of self-deception is very s Johnston argues that acts of self-deception (and wishful thought) must be unintentional unless they involve the development of positive beliefs. This is significant to psychoanalytic explanation because intentional self-deception does not seem very deceptive. That is, I cannot actively cause myself to believe something that I overtly do not believe. The unintentionally of self-deception serves as corroborating evidence to the psychoanalyst. By holding a strong distinction between intentional and unintentional beliefs, we can infer, says the psychoanalyst, that the mind is organized to separate these belief categories. Once we acknowledge that the mind is compartmentalized, psychoanalytic explanation becomes an important tool in the science of the mind.

One important issue regarding psychoanalysis is whether it is a methodological or ontological claim. Both horns of the dilemma are problematic. If psychoanalysis is merely a method of explaining cases such as wishful thinking and self-deception, then the problem of contradiction still stands, since the undivided mind holds contradictory beliefs. Alternatively, if psychoanalysis attests to accurately explain the mechanisms of the mind, then we have a problem in verifying (and falsifying) the theory.

Erwin's article discusses the effectiveness of psychotherapy. Erwin argues that meta-analysis of psychotherapy techniques cannot accurately indicate its effectiveness. Meta-analysis is a method of converting descriptive studies into statistically comparable results. Erwin is skeptical about the meta-analysis project as a method of determining the adequacy of psychotherapy. He states that meta-analysis is no more scientific than descriptive analyses. Additionally, Erwin considers the use of placebos in psychotherapeutic testing. Erwin supports the use of placebos and argues against some objections to placebo use in psychotherapy (particularly the problem of defining an adequate psychological placebo). His article is not only relevant to clinical psychology, but also to the more general problem of psychoanalytic explanation. By justifying the effective use of placebos in psychotherapy, Erwin implicitly gives evidence supporting psychoanalytic explanation, since psychotherapy uses psychoanalytic ideas in its treatment.

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What is a Good Materialist?

	Searle is right about functional theories being centered around goals or outcomes that we deem important (like assigning a purpose to the heart pumping blood instead of just saying that it just does that, period). Anything normative (like the goal of pumping blood, in this case) is going to detract from the empirical evidence and will assign to the system (like the circulatory system) an "as-if" intentional state.  On the surface, this may be a good argument for eliminativism (despite the fact that Searle, himself, is a strong defender of phenomenal consciousness); however, there are those like Van Gulick, Goldman, Flanagan, and Block that espouses that consciousness is the result of interactions between different processes on a global level.  This opens the door to exploring phenomena like consciousness, freewill, and other such concepts and either tries to make allowances for them into our materialistic theories or to come up with an argument of why we can't.  And so, the question is "Which is good materialism?  Eliminative materialism or 'robust' materialism?"
	Eliminative materialism is in keeping with the overall philosophy of empiricism.  What really is relevant is what we actually see or experience. We don't see anything that could lend itself to something like consciousness.  All we really see is behavior, and the only reason why we are even interested in consciousness at all is because of introspective inquires of our own mental processes.  This is what lead Descartes into thinking that there was non-material thinking stuff in the first place.  However, there's a problem here.  On what grounds can an eliminativist say that none of what is expressed in this non-material stuff is important?  Any argument along those lines would be normative.  If the eliminativist wants to eliminate consciousness as irrelevant and confused, then he or she will have to rely on a normative position that attributes to this individual (the eliminativist him- or herself) an intentionality.  In other words, there is a conceptual problem, to say the least, in eliminativism.  It is grounded on a normative position that eliminates the very intentionality that is spawned from the position, itself.  This is analogous to Garrett's argument that despair causes the very irrationality and immorality that it predicts (Garrett, The Problem of Despair).  Here, eliminativism totally reduces its very goal into an irrational (or confused) philosophical position.
	"Robust" materialism, on the other hand, doesn't deem that intentions and other normative concepts are irrelevant.  It only says that the underlining processes that make consciousness possible are not normative.  There are blind neurological properties that converge and that allows things like beliefs, intentions, and other subjective notions to take fruit.  Although this 'robustness' doesn't strictly stay in the arena of materialism (or even in the arena of empiricism), it does take concepts not given in sense perception (concepts that are expressed in an immaterial thinking substance) and tries to square them into a materialistic framework that justifies human experience in the first place (and since empiricism is driven on the experiences of the observer, this seems to be a worthwhile venture).
	And so, what makes a good materialist?  The eliminativist tries to be true to the very spirit of empiricist materialism, but he or she then reduces the very goal into a confused position.  On the other hand, the "robust" materialist doesn't stay true to strict empiricist materialism, but the intent is that he or she wants to show that everything that we experience is accountable to a physical substance.  Plus, he or she doesn't collapse the intentionality of taking the materialist position in the first place.  I feel that "robustness" is the way to go, but, then again, I am not a materialist.  What do you think?

This week's readings are about consciousness, yet again, but this time with a twist. It isn't consciousness itself which is the focus of all five papers, but rather what we can learn about consciousness from examining situations where it doesn't seem to be rearing its ugly(?) head. Each author has their own tidbits to throw into the mill, and their own conclusions to draw from the data, but what they all are considering is how brain damage disorders can tell us about consciousness.

Martha Farah does the best job outlining the types of disorders interesting to us, and the sorts of theories of consciousness we have to check against the empirical data. She cites three main groups of theories about consciousness, the first of which is a "priveleged role" type account, where consciousness is supposedly the explicit function of some system in the brain. The second type is an "integrated state" approach, where the state of many different systems gives shape to consciousness as we know it. The third type, which ultimately she thinks has the most support, is a "graded" model, where consciousness is a result of the quality of the perceptions.

These categories seem at least somewhat useful, as the models discussed by each of the other authors this week seem to fall nicely into these categories. But more important, I think, is her discussion of disorders. She gives good discussions of blindsight, prosopagnosia, perception and neglect, and pure alexia. She discusses the empirical data for each of these, and then discusses how she thinks each of the types of models above would account for the data.

The most important conclusion she draws from this discussion of disorders and theories, though, is that these disorders do not present a single problem. Farah thinks that these disorders cannot share a single cause, and so will each tell us different things about consciousness, if they tell us anything. She still thinks that a "graded" model of consciousness accounts best for the data from all the disorders, but hopes that further research will be done.

Bernard Baars presents a method for studying consciousness, very much in line with what Farah actually discussed in her discussion of the empirical data we have on disorders. He proposes we use "contrastive phenomenology"; that is, that we examine situations in which a person would normally have a "conscious" experience, but isn't, and try to discover from an analysis of the differences what it is that consciousness is doing. He then presents some examples of where to apply his method, but Farah's discussion is more concrete.

Patricia Churchland is a bit more general, and a bit mores specific. More general, in that she argues not for a specific research method, but for the use of a reductionist research paradigm. She believes a reductionist research program would conduct research simultaneously at many different levels, and take into account data from them all, in the hopes of getting a better picture of the mind overall. Consciousness is not necessarily the goal here, but as a phenomenon it is useful to study. She is more specific in the way that she approaches theories of consciousness. She cites two specific theories about visual awareness, and then discusses them in detail, as well as their explanatory power.

Edoardo Bisiach has on his mind the destruction of the concept of the unity of mind, or at least of consciousness. He arrives at a conclusion similar to Farah's conclusion that brain disorders will tell us different things about consciousness. But he takes the evidence for that conclusion to be saying something stronger, and so concludes himself that it isn't just that they will tell us different things about consciousness, but that they disorders affecting discrete compositional parts of consciousness. So, for Bisiach, the data suggests that there is no unity of consciousness.

Tim Shallice needs an editor. But besides that, his main goal is to discuss critically the empirical data available about disorders, and the conclusions we can draw about them for consciousness. More particularly, he discusses blindsight and "split-brain" patients. He concludes from his discussion that there are many different theories about consciousness (Really? ;), and then suggests than none of them will work, since he wants to reject the "priveleged role" type account that Farah presented, and of which type he claims all the theories he discussed were members.

Hope this is helpful; there was a lot to read, and I didn't feel like re-writing it all. :)

This week's reading presents arguments for and against the existence of basic color categories (BCC). Hardin argues that such categories do in fact exist in human perception, citing numerous studies in psychology, neurophysiology, and anthropology. Van Brakel objects to Hardin's conclusion, claiming 1) that in many cases the studies Hardin cites are suspect, 2) the empirical data doesn't support the conclusion of BCCs, and 3) several studies suggest contrary evidence.

Hardin's book, COLOR FOR PHILOSOPHERS, presents a long argument drawing from the psychology of perception, physiology of the retina, and anthropological studies to show that we, qua humans, have a particular set of BCCs. He suggests that there are six primary colors: black, white, red, yellow, green, and blue. Additionally, humans classify colors as pink, orange, brown, purple, and grey. These colors, while they are a mixture of two or more primary colors, are recognized as distinct and thus deserve their own BCC, at least socially if not biologically.

Hardin spends the most time discussing the physiology of the retina, especially the pigment cells, rods and cones. He explains that there are three basic types of cones: short-, medium-, and longwave. He argues that each of these can be correlated physiologically with particular primary colors. Hardin infers that we have a biological primacy for perceiving certain colors, particularly red, yellow, green, and blue. This is not merely an accident of our language but a fact of our physiology.

Further, the primary colors are perceived according to an opponent system of three color pairs: red/green, blue/yellow, and white/black. This physiological fact is significant because of its correlation with information we have regarding the psychology of color perception. While we recognize that orange is a mixture of red and yellow or purple is a mixture of red and blue, we do not recognize any color that results from mixing red and green or blue and yellow. Hardin argues that these opponent colors CANNOT be mixed due to a physiological limitation. Red and green are perceived through opposing processes of the same retinal cells; thus seeing one necessarily prevents seeing the other (and similarly for blue and yellow). Hardin concludes that our scheme for BCCs is limited due to these opponent systems. Also, the six basic colors are primary and categorically separate because of our biology.

Hardin's main argument in the third chapter is based on a study by Berlin and Kay (1969) who tested different people across many different languages and cultures as to how they categorize colors. Berlin and Kay used 320 color chips of maximum saturation but varying hues and brightness from across the range of visible light. The subjects were asked to group the chips into different color classes. According to Hardin, the study indicates that humans universally classify all color variations into eleven groups, the six primary colors and pink, purple, orange, brown, and grey. Moreover, there was a natural progression to the order in which the colors are chosen. Hardin states that in all cases, black and white were considered by the subjects to be the most primary or first chosen colors. Next, red was chosen, followed by either yellow and green (in no particular order), then blue, and finally the five additional colors (in no particular order). Some cultures and languages distinguished fewer than eleven BCCs–some as little as two. In these cases, the subjects chose classes according to the same order. In other words, all those cultures with four BCCs had black, white, red, and either green or yellow, but not both green and yellow and not blue.

Hardin infers from this data that not only do we have a natural system of eleven BCCs but that there is a natural evolution of the colors, beginning with black and white, moving to red, then yellow or green, and so on. The evidence from the Berlin-Kay study shows that colors are not ingrained in a language or culture, but in some lower level, i.e. biological, state. As further support, Hardin cites studies where people whose languages do not make particular color distinctions more easily learn to classify colors from across BCCs than from within BCCs. So, If a person's language does not distinguish red and pink, she will initially not distinguish the colors (presumably, she will classify shades of pink as shades of red). If she is presented with several Mansell chips of shades of red and pink, she will quickly and easily learn to separate the two. But, if a similar experiment is performed where the chips are different shades of red, the subject is much slower and less successful in distinguishing maroon from scarlet.

Hardin cites several other studies that he believes suggest biologically extant BCCs. These include studies where infants and small children who have no or very limited use of language also make color distinctions. He is also unmoved by inverted and shifted spectrum arguments, claiming that the biological basis of color vision makes such cases unrealistic or outright impossible. Similarly, Hardin claims that the problem of multiple reliability in reducing psychological color categories to physiological color categories is not at issue. Generally, Hardin's position is that BCCs are a HUMAN phenomenon, so issues regarding misconnected or non-humans is irrelevant to his discussion.

Van Brakel responds to Hardin's arguments primarily by attacking the Berlin-Kay study and Hardin's interpretation of the results. He also discusses some other philosophical mistakes Hardin makes in his book. Van Brakel concludes that there is no neurophysiological data that supports a biologically ingrained system of color classification nor do the psychological and anthropological studies of Berlin and Kay suggest such a classificatory system.

Van Brakel's attack on the Berlin-Kay study comes from several fronts. First, he preludes his objections by pointing to earlier color distinctions based upon the spectrum. The original seven color system of Newton (Roy G. Biv) is completely arbitrary, with very particular and unnatural conditions required to see seven distinct colors. Discussing Berlin and Kay directly, van Brakel questions the methodology used by the researchers. He states that the study was biased from the starting block because of their use of the Mansell coloring system which is based on a western division of colors. Also, the study, which intended to determine BCCs based upon the basic color terms (BCTs) of a language presumed that BCTs serve only a functional role in color discernment, while in several cultures, color terms–both the names themselves and the number of names–have significant cultural and mythical implications that effected the results of the study.

Van Brakel also questioned the way in which the study defined color terms. Hue, saturation, and brightness are loaded components of color derived from our language (at least potentially). Many languages separate colors not only according to their appearance but according to the object to which they are attached. For example, we have a hair color category of BLONDE, yet we generally do not think of blonde as a color in any other circumstance. In this instance the Berlin and Kay study might say something like, "In English, BLONDE is a shade (subset) of YELLOW." The most important criticism of Berlin and Kay's methodology, according to van Brakel was their use of the evolutionary sequence of color categories. If a subject did not pick out black and white as their first color categories, the researchers assumed them to exist anyway. Also, if a subject picked as the fourth color a term that meant green, and blue (since some languages do not distinguish these colors), the researchers assigned it the value GREEN, since green comes before blue in their evolutionary schema. This arbitrary placement happened in several cases.

Van Brakel concludes that we have no reason to accept the eleven basic color categories defined by the Berlin-Kay study or any similar study. More importantly, he feels that no such anthropological evidence supports any universal color categories existing across human languages.

Next, van Brakel discusses Hardin's arguments regarding the physiological basis for color categorization. Van Brakel claims that Hardin makes several hasty inferences and fails to see the complexities of visual psychophysics. Hardin discusses in great detail the workings of the retinal photoreceptors, but he still glosses over key details. First, the information about the opponent systems involved in vision only discuss boundaries and achromatic distinctions without reference to color or hue. Second, Hardin's psychophysical account begs the very tricromatic color system it presumes to describe. Van Brakel says that we do not have enough knowledge of the workings of the brain to infer Hardin's model. Finally, van Brakel contends that the psychophysical information that Hardin presents does not support his reductive materialism regarding color perception. Hardin wants to reduce our trichromatic color system to the tripartite of cones in the eye, yet we not only have no good reason to do so, but the reduction does not yield the right connections between phenomena.

Van Brakel concludes by suggesting that we should view color naming and categorization in a functional manner. This explains both the cross linguistic similarities and differences and emphasizes the arbitrariness of color categories without suggesting categories do not exist.

Color categories appear to be among the most biologically

determined domains to which humans apply language. Perhaps it 

is because of this stubborn, physiological reality that people 

who wish to emphasize cultural relativity struggle so mightily 

in their arguments for arbitrariness in color names.

A more promising, if less black and white (pun), line of 

reasoning is to array domains on a continuum of degree of 

cultural relativity.

In a paper in Cognition (1977, pp. 215-233), with Miyake and 

Muto, we studied the culture-boundedness of referential 

messages by Japanese and American students describing abstract 

figures by translating the descriptions between languages and 

having students in the opposite culture try to understand 

which figure (out of 16) was being described. Although many 

messages translated well between cultures, others were highly 

culture bound, showing the effects of culture (as well as the 

more universal aspects of perception and language).

It would be interesting to replicate the study with 16 hard to 

describe colors, perhaps.

PS: I came in on this discussion because I read that Dr. 

Hardcastle was presenting on a PBS satellite conference on 

Using the Web to Enhance the Classroom and visited her site, 

saw her on WebCam, called her, and received almost immediately 

a copy of a paper she wrote, which was useful in my research 

on how to study learning in Web-based courses. Thanks for the 

chance to drop in on your class. Patrick Dickson, Professor, 

Director, Technology Exploration Center, Michigan State 

University. pdickson@pilot.msu.edu

This weeks readings were verybroad (and long). So I've given up on providing a complete summary of everything that was said, and will instead endeavour to give a summary of what was said about the mechanisms of visual processing, the function of attention, and the models proposed. The specific models discussed (in some cases not so specific) we will hopefully draw a better picture of in class, for those who aren't clear. In a sense, I don't think a mere summary is good enough with some of these models, since there are some very clear flaws - and other models are vague enough that a summary would be empty.

So, a brief summary of the different authors' views on visual processing, and the function of attention.

I. Visual Processing - How it works.

LaBerge presents ample evidence, I think, that visual processing is modularized. There are two main pathways (although he makes it quite clear that this is a rough treatment - there is quite a bit of crosstalk, or the potential for it), one of which handles color, shape, identity, etc., and the other of which handles primarily location information; the "what" and "where" of visual perception. Each of the other authors we read for this week accepts this basic distinction, although at least Schneider wants to claim this is only a structural, not a functional modularity.

LaBerge takes this modularity merely as a note about where and how vision is actually processed, and goes in depth into the actual connections involved between the pathways to build his model. The rough picture he provides is one in which the level of interconnectivity, both direct and through other areas (e.g., the superior colliculus (SC), and the post-parietal cortex (PPC)) between these paths makes the distinction a little weaker.

Van der Heijden notes the modularity, and then declares that this is not a problem - that in fact, the modularity is just a division of processing. He spends significant time arguing for the absence of a binding problem - more precisely, claiming that the "what" and "where" don't need to be recombined. He then points out that his model does recombine them, by taking the output of the "where" path, and feeding it back into the visual system input. So he believes that his model provides a solution for the (nonexistant) binding problem.

Treisman argues that the binding problem does exist because of this modularity, and unsurprisingly thinks her model solves this problem.

Tsal, et. al, propose to divide up visual processing even more. While there is evidence presented in LaBerge for the further division of color, shape, and perhaps one or two other aspects of visual processing, Tsal and friends wish to discuss color, shape, curvature, orientation, and location "dimensions" of visual perception. Each of these they suggest evidence for, froma variety of experiments.

Schneider, lastly, views this modularity as a structural, not a functional, feature of the brain. He claims that information is in fact parsed "globally", and that this modularity show only how each "local" aspect of information is parsed in a different place. Why does he think he has something new to offer with this? Because he proposes that neuronal synchrony, that is, the synchronous firing of neurons, is what identifies the global structure that is being processed in these different places.

II. (Visual) Attentional Processing - What does it do?

LaBerge has the most common-sense view of what it is attention does. For him, attention is merely the enhancement of the attended area, and the degredation of the surround. So attention is essentially a contrastive process, which he thinks can occur by (1) enhancement of the attended area greater than the enhancement of the surround, or (2) degredation of the attended region less than the degredation of the surround, or (3) enhancement of the attended region and degredation of the surround. So for him, attention is what makes us "more" aware of one thing than the rest of our environment.

Van der Heijden thinks that attention is designed to solve two problems, namely the problem of selecting an action, and selecting an object for that act. He argues that these are not only nice goals for attention from a neurobiological point of view, but from an evolutionary standpoint. HIs model is designed with this in mind, and is a result of his quest to identify "attention" with "behavioral modification".

Treisman proposes that the single most important function of visual attention is solving the binding problem. Specifically, by telling us which object is where, and which one it is that we are interested in, amongst those out in the world. She calls this the "featural integration" model.

Tsal, et. al, have a more abstract conception of what it is that attention does, that may encompass the function of both Van der Heijden and Treisman's models. They propose that attention determines what location in the multi-dimensional visual-perception space that an object occupies. Namely, where it lies with respect to the axes of color, shape, spatial location, etc. The bulk of their paper is spent justifying the actual dimensions of this space; this function of attention is mostly a proposal, not a conclusion.

Schneider claims that attention is what solves the binding problem, among other things. In specific, he thinks attention accounts for "similarity effects", "local feature contrasts", and "conjunction search."

III. Attentional Processing - The models.

LaBerge proposes that attentional processing is carried out by thalamocortical circuits - by the transfer of information to and from the cortex from the thalamus. He thinks that the information coming into the visual system is selectively amplified when it comes through the thalamus, and that this amplified information is fed back to the system. It is somewhat unclear what the complete picture is, since he also discusses attentional processing occurring in the superior colliculus - where he thinks the location of attention is determined. Further, he mentions attentional processing going on in several other regions of the brain - although I may be comfusing this with expressions of attention.

Van der Heijden doesn't go into neurobiological models. His model is a functional one, proposing that the modularity of visual processing doesn't really affect the system. He thinks that the output of location processing is fed back into the input of the whole visual processing system, so that it is carried through along with the "what" information. This seems to be the real key of his model, and an easy point for dispute.

Treisman doesn't discuss her model in much detail at all, except to say that it is compatible with Van der Heijden's model to a great extent, and that it allows for attention to be directed by an external process.

Tsal, et. al, don't discuss neurobiological implications, either. They just discuss what they think the function of attention is, and propose that as their model of attentional processing.

Schneider, finally, proposes a model based on three functions: "stimulus driven and attentional segmentation, attentional selection via V1", and "what- and where- based attentional control." Segmentation is the parsing of visual input into shape, color, location, etc., for each specific "object" in the visual field. Attentional selection is accomplished by back-referencing to V1 to get location information lost in the "what" pathway. What- and where- based attentional control are proposed as solutions to identifying an object with and without distractors, respectively.

Just wondering.

Sir John Eccles