lcs 11: cognitive science - modules - claremont colleges · pomona college lcs 11: cognitive...

Pomona College

LCS 11: Cognitive ScienceModules

Jesse A. Harris

February 5, 2013

Jesse A. Harris: LCS 11: Cognitive Science, Modules 1

Agenda

Group question 1.31. Leader discusses response to group2. Group discussion with summary of points3. Class discussion

Modules1. DeVnitions2. Examples from visual processing

Reading for next class

Response paper #1


GQ 1.3

GQ 1.3Take a simple action or mental process of your choosing andidentify at least three distinct subprocesses that might beinvolved in performing that action or process. Which, if any, ofthose subprocesses might be called modular in Fodor’s (1985)sense, and why?

Group leadersSam, Audrey, Lea Lynn, Daniel, Joel, Noah, Jun, Sarah, Paul


Cluster of concepts

1. Domain speciVcity

2. Informational encapsulation

3. Mandatory operation

4. Fast processing

5. ‘Shallow’ outputs

6. Fixed neural architecture

7. Characteristic and speciVcbreakdown patterns

8. Characteristic ontogenetic paceand sequencing


Subcluster 1: Modules are snobs

Domain speciVcityA module operates over or responds to only a narrow range ofinputs. A special purpose mechanism that provides answers tovery speciVc questions.

Is there an edge in a particular area of the visualVeld?


Subcluster 2: Modules don’t care what you think

Information encapsulationInformation processed within a module cannot be accessedfrom information outside that module.

Modules do not consider other types of informationoutside their speciVc domain, including top-downknowledge.


Subcluster 3: Modules are dumb

MandatoryOnce the module receives its input, it automatically operateson the information it receives.

FastAlthough a relative term, modules Vnish their computationsquickly.

ShallowModules produce constrained output that wascomputationally cheap to produce.


CAT


Subcluster 4: Modules are innate

Fixed neural architectureFunction associated with module is localized to a speciVc setof neural structures.

Characteristic breakdownModules are independent: when they fail, they may do soindependently of other cognitive functions.

Characteristic paceModules tend not to be learned, but rather ‘triggered’ byspeciVc developmental stages.


In short

Modules are dumb snobs, who don’t care what you think. Andyou have to put up with them.


Thatcher illusion (Thompson, 1980)


Thatcher illusion (Thompson, 1980)


Thatcher illusion


Vertical pathway Horizontal pathway

Photoreceptors (rods & cones)

Bipolar cells

Retinal ganglion cells

!"#$%"&'()*+,))-*

./(+#$&,*+,))-*

Hubel & Wiesel, 1959. Domain speciVcity.

http://www.youtube.com/watch?NR=1&v=4nwpU7GFYe8


Lateral geniculate nucleus (LGN

Two kinds of neuron in LGN

1. Magnocellular neurons.Deeper within LGN; thickeraxons, which allow a quickerresponse. Project onto wherepathway.

2. Parvocellular neurons.Shallower within LGN;thinner axons, respond moreslowly to input. Project ontowhat pathway.


http://www.youtube.com/watch?v=nFJvXNGJsws

http://www.youtube.com/watch?NR=1&v=4nwpU7GFYe8

http://www.youtube.com/watch?v=nFJvXNGJsws

Split brain studies. Information encapsulation.


Split brain studies. Information encapsulation.

http://www.youtube.com/watch?v=ZMLzP1VCANo


Stroop task. Modularity par excellence.

Stroop taskName colors of word, not the word itself. If you see the wordBLUE, say “Red” not “Blue”. If there is no word, just say thecolor that you see.

Self-demoCover up all but the Vrst column with a separate piece ofpaper. When I say START, start the task silently. When youare done, look up and jot down your response time at thebottom of that column. We’ll then do the same for the othercolumns.

http://online-stopwatch.chronme.com/


Stroop task. Modularity par excellence.

Stroop eUectTakes longer to name the color when the printed word isincongruent. Also, more likely to misname item.

ModularityHow is this result compatible with modularity?


http://www.youtube.com/watch?v=ZMLzP1VCANo

http://online-stopwatch.chronme.com/

Scope of modularity

Central processing systemsInput provided by modules is evaluated, assessed, andtransformed by more global mechanisms, which areresponsible for interpretation.

. . . Nature has contrived to have it both ways, to get thebest out of fast dumb systems and slow contemplativeones, by simply refusing to choose between them. That is, Isuppose, the way that Nature likes to operate: “I’ll havesome of each” – one damned thing piled on top of another,and nothing in moderation, ever. (Fodor, 1985: p. 4)


Scope of modularity

Modest modularityModularity limited to simple input-output systems, systemsthat translate an external stimulus into information to form amental percept. Such systems are sometimes called sensorytransducers.

Fodor’s claimModules are the only parts of the cognitive system that wecan ever hope to fully understand within a scientiVc theory.Non-modular components cannot ever be captured by a fullyscientiVc theory.


Massive modularity

I No central processorI Mind is entirely modular, but with a

weakened notion of moduleI Information encapsulation is no longer

a property of a module

1. Biological systems are designed incrementally,requiring modular organization

2. Human minds are ‘extensions’ of animalminds, which are modular

3. Argument from computational tractability

See Cosmides and Tooby (1992) and Carruthers (2006)

Phrenology


Some issues with modularityIssue 1: Neuroplasticity.The brain shows some degree of Wexibility; functional deVcitscan sometimes be recovered by remapping or recruiting otherneural areas.

Issue 2: Domain speciVcity.Really part of issue 1: Multiple areas of the brain seem to takein multiple sorts of inputs.

Issue 3: Limitations on science.We’d like to be able to study more than just sensorytransducers – what happens during higher order processingand how does the mind make sense of that low levelinformation?


Next time: Connectionism & Neural nets

No GQ for next time

Reading is diXcult, so try to get a feel for how neuralnets work, without sweating the details.

Writing response # 1 due by Friday at 5PM – upload toDropbox on Sakai.


lcs 11: cognitive science - modules - claremont colleges · pomona college lcs 11: cognitive...

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