Tuesday, November 4, 2014

How the mind works: It's the information stupid!

Not that I'm calling anyone stupid.  That's a reference, of course, to Clinton campaign manager James Carville's "It's the economy, stupid." It's a call to refocus the emphasis.  Here we're talking cognitive science and the relation between computational theories and embodied theories of the mind and the need to refocus our emphasis on information processing.

I contend that embodied theories are, under the hood, computational (i.e., information processing) theories and that the embodied folks are mischaracterizing computational theories.  Or at the very least they using one such theory (~Fodorian philosophy) as representative of the whole cognitivist/computational mindset.  In fact, it’s always been about information and how it gets processed.  It doesn’t matter how you process the information—neurons, electronic switches, gears, pumps—it just matters that information (patterns of physical stuff that correlate with the state of the world) is used in such a way as to guide behavior. To try to make this clear, here’s an excerpt from The Myth of Mirror Neurons discussing some early conceptions of cognitive psychology.  
Psychologist Ulric Neisser, who literally named the field and wrote the book on it with his 1967 text, Cognitive Psychology, defined the domain of cognition this way:
“Cognition” refers to all the processes by which the sensory input is transformed, reduced, elaborated, stored, recovered, and used.  … Such terms as sensation, perception, imagery, retention, recall, problem-solving, and thinking, among many others, refer to hypothetical stages or aspects of cognition.[1]
Neisser’s table of contents underlined his view that cognition was not limited to higher-order functions.  His volume is organized into four parts.  Part I is simply the introductory chapter.  Part II is called “Visual Cognition” and contains five chapters.  Part III is “Auditory Cognition” with four chapters. Finally, Part IV deals with “The Higher Mental Processes” and contains a single chapter, which Neisser refers to as “essentially an epilogue” with a discussion that is “quite tentative”. He continues,
Nevertheless, the reader of a book called Cognitive Psychology has a right to expect some discussion of thinking, concept-formation, remembering, problem-solving, and the like…. If they take up only a tenth of these pages, it is because I believe there is still relatively little to say about them….
Most scientists today working on perception or motor control, even at fairly low levels, would count their work as squarely within the information processing model of the mind/brain and therefore within Neisser’s definition of cognition.  Consider this paper title, which appeared recently in a top-tier neuroscience journal: Eye Smarter than Scientists Believed: Neural Computations in Circuits of the Retina.  If anything in the brain is a passive recording device (like a camera) or a simple filter (like polarized sunglasses) it’s the retina, or so we thought. Here’s how the authors put it:
Whereas the conventional wisdom treats the eye as a simple prefilter for visual images, it now appears that the retina solves a diverse set of specific tasks and provides the results explicitly to downstream brain areas.[2]
Solves a diverse set of specific tasks and provides the results… sounds like a purpose-built bit of programing—in the retina!  We observe similar complexity in the control of simple movements, such as tracking an object with the eyes, an ability that is thought to involve a cerebral cortex-cerebellar network including more than a half dozen computational nodes that generate predictions, detect errors, calculate correction signals, and learn.[3]

---end excerpt--

My former post doc advisor, Steve Pinker, who is arguably today’s champion of the computational theory of mind and a staunch defender of "symbolic processing" (it's not what you think!) reinforces the broad definition of computation as just being about information processing:  
the function of the brain is information processing, or computation… Information consists of patterns in matter or energy, namely symbols, that correlate with states of the world. That’s what we mean when we say that something carries information. A second part of the solution is that beliefs and desires have their effects in computation—where computation is defined, roughly, as a process that takes place when a device is arranged so that information (namely, patterns in matter or energy inside the device) causes changes in the patterns of other bits of matter or energy, and the process mirrors the laws of logic, probability, or cause and effect in the world. [4]
Notice that symbols are defined simply as patterns in matter or energy, not x’s and y’s in lines of code.  The patterns “represent” (i.e., correlate with) states of the world.  This constitutes information that brains can make use of by changing the patterns, e.g., taking interaural time difference and using that information to guide head movement. This is why the embodied movement is so puzzling to me.  It’s fundamentally no different that the computational theory of mind.  Does the body contribute something to information processing?  Of course!  The brain evolved with the body to solve survival problems.  The body shapes the input to the brain. But that doesn't mean that the brain isn't processing information.  


1 Neisser, U. (1967) Cognitive psychology. Appleton-Century-Crofts
2 Gollisch, T. and Meister, M. (2010) Eye smarter than scientists believed: neural computations in circuits of the retina. Neuron 65, 150-164
3 Wolpert, D.M., et al. (1998) Internal models in the cerebellum. Trends in Cognitve Sciences 2, 338-347


3 comments:

Dominik Lukeš said...

I think there some problems of terminology as well as substance here. The terminological problem is that while both 'information processing' and 'computation' can be used in the sense you do, the vast majority of non-experts (and by the look of it, a lot of the experts, as well) don't use them that way or at the very least cannot quite use them that way in all contexts.

Information in the pure Shannonian sense is just a formal restatement of things like energy or matter. There is nothing inherently symbolic about information. But most people interpret information in a symbolic (or an even more crudely representational way). But you don't seem to (despite that bit in the Pinker's quote).

Equally, while computation does not have to be digital or algorithmic, the vast majority of people think of digital algorithm processing when you say computation.

So for example, you could say that a foot walking along a rocky path is processing information it receives from the terrain and computes the appropriate response. But this is a non-symbolic, non-algorithmic, analog process that looks nothing like what you'd find inside a CPU. In fact, these insights seemed to have enabled some great advances in robotics (starting with Rodney Brooks' MIT work).

Having looked briefly at the retina paper, it seems that even the "retina's intelligence" is of this kind, except the authors chose to describe it in an algorithmic symbolic matter. (But I don't have enough background there, to be certain.)

So what you call information processing, many people would call interaction, and what you call computation, many people would call reaction.

But what happens when you hear a word? I would argue that you simply cannot describe the process successfully purely as a matter of symbolic algorithmic information processing. Yet, it's clearly more than what goes on when a foot meets the road. At the same time, in many ways, it's probably more similar to that than what goes on inside a computer that's trying to process a word.

What about something even more volitional like trying to rotate a map in your mind to match what you see around you? Or doing mental arithmetic? This is clearly emulating symbolic algorithmic processes. But are the underlying neural computation of that nature at all? Isn't entirely possible that they are neither symbolic nor algorithmic? Which is really what this debate seems to be about.

So the issue is that talking about information processing evokes metaphors that steer you towards thinking about serial algorithmic operations on symbols whereas what's going on is massively parallel processing of what for a lack of a better term I'd call pseudo-symbols - patterns matching patterns without the crucial aspect of convention that is integral to the definition of symbol.

So the substantive argument happens in between and alongside a terminological one and it's hard to tell which is which at any one time.

Greg Hickok said...

Thanks, Dominik. You've made some excellent observations, which highlights that the debate is really about what to call the stuff that the brain does, not fundamentally about how it does it. It's transforming information to accomplish a task. That is what traditional cognitive psychologists believe and I think that is what embodied theorists believe. It's a false dichotomy spurred on by preconceptions as to what counts as symbolic or computational or representational.

Andrew Wilson said...

Funny you should rely on Neisser. He followed up that book with 'Cognition & Reality' where he pinged cognitive science for not paying enough attention to the fact that "the amount and kind of processing a stimulus is assumed to undergo necessarily depends on related assumptions about the nature of that stimulus'. He'd read Gibson by this point and although he never self-identified as an ecological psychologist he got a lot more ecological in his thinking and this critique of cog sci in general reflects Gibson's success from actually acknowledging this fact and from the fact no one else seemed to be worried.