Neuro 95:Neuro 95:Foundations of NeuroscienceFoundations of NeuroscienceHistory & Philosophy ModuleHistory & Philosophy Module

Brian KeeleyBrian KeeleyPhilosophy, Pitzer CollegePhilosophy, Pitzer College

Office: Broad Hall 107Office: Broad Hall 107

Lecture 2

Dion Scott-KakuresDion Scott-KakuresPhilosophy, Scripps CollegePhilosophy, Scripps College

Office: Humanities Bldg #215Office: Humanities Bldg #215

HousekeepingHousekeeping

Assessment: Assessment: An An in-class exam in-class exam on last on last day of module (be able to identify and day of module (be able to identify and talk about the significance of some talk about the significance of some quotations & discuss some of the quotations & discuss some of the philosophical arguments we’ll be philosophical arguments we’ll be considering) considering)

Today’s ReadingToday’s Reading Patricia ChurchlandPatricia Churchland, , "Functionalist "Functionalist

Psychology"Psychology"

Reductionism vs. AntireductionismReductionism vs. Antireductionism Neuroscience, Psychology, Physics, Neuroscience, Psychology, Physics,

Economics are all sciences Economics are all sciences (purveyors of (purveyors of different theories with different ontologies/ different theories with different ontologies/ taxonomies/vocabularies)taxonomies/vocabularies)

Question:Question: What is the relationship What is the relationship between these theories (especially as between these theories (especially as they apply to the exact same region of they apply to the exact same region of space-time; e.g., your suitemate)?space-time; e.g., your suitemate)?

““Completed Science”/ “The end of Completed Science”/ “The end of Science”Science”

Reductionism vs. …Reductionism vs. … Reductionists are those who argue that Reductionists are those who argue that

there really is only one, true scientific there really is only one, true scientific theory.theory.

Ernest RutherfordErnest Rutherford (The “Father of Nuclear (The “Father of Nuclear

Physics”):Physics”): "All science is either physics or "All science is either physics or stamp collecting”stamp collecting”

… … vs. Antireductionism vs. Antireductionism Antireductionists are those who argue Antireductionists are those who argue

that theories at different levels are that theories at different levels are autonomous & independent of one autonomous & independent of one another.another.

Psychology need not coordinate it’s Psychology need not coordinate it’s theory with neuroscience anymore than theory with neuroscience anymore than Economists need to square their theories Economists need to square their theories of inflation with quantum mechanics.of inflation with quantum mechanics.

One influential set of arguments for One influential set of arguments for antireductionism comes from the antireductionism comes from the philosophical school known as philosophical school known as “Functionalism”“Functionalism”

… … vs. Antireductionism vs. Antireductionism Jerry Fodor:Jerry Fodor: “ “It isn't, after all, seriously in doubt that It isn't, after all, seriously in doubt that

talking (or riding a bicycle, or building a bridge) depends talking (or riding a bicycle, or building a bridge) depends on things that go on in the brain somewhere or other. If on things that go on in the brain somewhere or other. If the mind happens in space at all, it happens somewhere the mind happens in space at all, it happens somewhere north of the neck. What exactly turns on knowing how north of the neck. What exactly turns on knowing how far north? It belongs to understanding how the engine in far north? It belongs to understanding how the engine in your auto works that the your auto works that the functioningfunctioning of its carburettor is of its carburettor is to aerate the petrol; that's part of the story about how to aerate the petrol; that's part of the story about how the engine's parts contribute to its running right. But the engine's parts contribute to its running right. But why (unless you're thinking of having it taken out) does why (unless you're thinking of having it taken out) does it matter it matter wherewhere in the engine the carburettor is? What in the engine the carburettor is? What part of how your engine works have you failed to part of how your engine works have you failed to understand if you don't know that?” (From understand if you don't know that?” (From Times Times Literary SupplementLiterary Supplement))

Score-card

Sterelny (& Fodor): Functionalist Pat Churchland: Eliminativist

Reductionist (but spends time explaining functionalism. She takes it seriously.)

Lycan: (Homuncular) Functionalist Bechtel, Mundale, Zawidsky, Craver (to be

read during final integrative module): Trying to find new ways of relating neuroscience and psychology

So what is “reduction”?So what is “reduction”?

What’s at issue here is “theories” (not phenomena)What’s at issue here is “theories” (not phenomena) TheoriesTheories—that is, structured sets of linguistic —that is, structured sets of linguistic

statements—are what either do or don’t get reduced.statements—are what either do or don’t get reduced. And, traditionally, it has been argued that one theory And, traditionally, it has been argued that one theory

(T(TRR) is ) is reducedreduced by another theory (T by another theory (TBB) when you can ) when you can

logically derivelogically derive T TRR from T from TBB..

So what is “reduction”?So what is “reduction”?

So, we say that modern chemistry is So, we say that modern chemistry is reducedreduced by modern physics because the by modern physics because the laws oflaws of chemistrychemistry (how molecules bind (how molecules bind or don’t bind, how acid works, etc.) can or don’t bind, how acid works, etc.) can be deduced from the laws ofbe deduced from the laws of physicsphysics (the behavior of atoms and electrons, (the behavior of atoms and electrons, etc.)etc.)

Or, for the visually-mindedOr, for the visually-minded

Law in TLaw in TRR

SS11 SS22

Law in TLaw in TBB

PP11 PP22

BridgeBridgeLawLaw

BridgeBridgeLawLaw

The The ExplanandumExplanandum or or ExplanandaExplananda (pl) (pl)

The The ExplanansExplanans

Functionalism: Levels of

explanation

In the Beginning…There was AI Back in the 1940s, Alan

Turing built one of the first computers, developed the science of computation and along the way, invented the science of Artificial Intelligence (AI).

(He also single-handedly won WWII.)

(1912-1954)

Universal Computing His idea: Computers can follow any

definable set of rules for converting inputs into outputs.

This is the notion of a “Universal Computer”. A device that can compute any process that can be formally described

Human, intelligent behavior is just a complicated way of converting inputs into outputs (Humans are very complex information processing machines.)

Hardware & Software

The mind is the software that runs on the hardware of the brain. Psychology figures out the program and AI ports it to a new platform, the digital computer.

(Cognitive) Psychology is the science of that information processing.

Computer engineering is the study of computer hardware

Neuroscience is the study of human hardware (“wetware”?)

AI happens when you set up an artificial info processor (a digital computer) to copy the formal properties of another info processor (a human).

Levels Example by way of analogy:

– Garry Kasparov vs. Deep Blue

3 Ways to explain Deep Blue’s behavior

Hardware Design Level - wiring diagram of the computer, the transistors and gates, magnetic and electrical states of the machine

Software Design Level - Deep Blue’s computer program

“Folk Psychological” Level - Deep Blue’s “knowledge,” “beliefs,” & “desires”

Some considerations Hardware Design Level - Most

complete explanation, but extremely detailed and difficult to obtain

Software Design Level - Relatively independent of the hardware level (programmers are largely ignorant of the details of hardware). Same software can run on different hardware.

Folk Psychological Level - A lot of predictive power, but is this kind of explanation merely a “useful fiction”?

Can we do the same thing for Kasparov?

Hardware Design Level - The neuronal wiring of his brain, states of his neurotransmitters, etc.

Software Design Level - The information processing of his “cognitive systems” (memory system, perceptual system, etc.)

Folk Psychological Level - His knowledge, beliefs, and desires

Multiple realizationMultiple realization An implication of the “computer An implication of the “computer

metaphor”metaphor” The mapping from mind to physical The mapping from mind to physical

substrate is one-to-many. One and the substrate is one-to-many. One and the same mental state—being in pain, same mental state—being in pain, believing George W. Bush is president, believing George W. Bush is president, etc.—can be realized in more than one etc.—can be realized in more than one physical way.physical way.

In a trivial fashion, each of us can be In a trivial fashion, each of us can be said to have the same beliefs, even said to have the same beliefs, even though each of our brains is physically though each of our brains is physically unique.unique.

Multiple realizationMultiple realization More extreme cases:More extreme cases: Left vs. Right hemispherectomy Left vs. Right hemispherectomy

casescases Human pain vs. Octopi painHuman pain vs. Octopi pain The possibility of artificial The possibility of artificial

intelligence intelligence Functionists take the phenomenon Functionists take the phenomenon

of multiple realization to entail that of multiple realization to entail that mental phenomena cannot be mental phenomena cannot be theoretically theoretically reducedreduced to brain to brain phenomena. phenomena.

Fodor’s PictureFodor’s Picture

Law in TLaw in TRR

SS11 SS22

WildlyWildlyDisjunctiveDisjunctive

PP11 P’P’1 1 P’P’2 2 …… P’P’mmPP22 PP33…P…Pnn

Many Disparate Laws in TMany Disparate Laws in TBB