理论化约之目的在将某一高层次理论化约到一个低层次理

1、Linking PropositionsDavida Y. TellerPresented by Allen HoungTheoretical Reduction 理論化約之目的在將某一高層次理論化約到一個低層次理論 例子：心理學化約到生物學 or Psychophysics化約到Physiology什麼是理論什麼是理論? ?理論包括：Language (vocabulary (terms & predicates), syntax)Inference rulesPostulates1. Theorems理論理論A如何化約到理論如何化約到理論B Bridge laws relate t

2、erms in both theories 理論A的所有的定理都可以由理論B的定理together with bridge law 推導出來，理論A能解釋的現象都能由理論B來解釋因果化約因果化約A可以因果化約到B，如果A-terms的指稱項的組成元素是B-terms的指稱項，並且B元素因果地產生A元素A定律所描述的規律是由B定律所描述的規律產生的1. Bridge laws不一定存在 A 可以因果化約到B，但不必然是可以理論化約到B 在這種情況下，A property supervenes on B property A supervenes on B iff no difference in

3、 A without difference in B 另一個說法是B決定APsychophysics化約到Physiology 這是理論化約 如果理論化約可以成立，則需要bridge laws Bridge laws就是所謂的Linking propositions的最強版本 Physical / Physiological statements Psychophysical / Phenomenal statementsLinking Proposition (Teller and Pugh)A linking proposition is a statement that links ph

4、ysiological and psychological terms in certain wayorPsychophysical linking hypothesis (Brindley)orPsychophysical axioms (Mller)The logical structure of general linking propositions : psychological terms : physiological terms initial proposition contrapositive converse converse contrapositive The ide

5、ntical family Identical Identical Non-Identical Non-Identical Identical Identical Non-Identical Non-Identical IdentityContrapositive IdentityConverse IdentityConverse Contrapositive Identity Identity and contrapositive identity are logically equivalent. But due to information loss, the mapping betwe

6、en brain states and phenomenal states cannot be 1:many, but 1:1 or many:1. Noise in stimuli and the neural system Identical physiological states seem not possible. Therefore, introduce statistical identity Statistically identical neural signals imply statistically indistinguishable sensations. Conve

7、rse identity and converse contrapositive identity propositions are not necessarily true. converse converse contrapositive Information loss Indistinguishable sensations do not necessarily imply identical physiological states Many (brain states) to 1 (perceptual states)? The process of vision = a sequ

8、ence of deterministic maps visual world retinal images the quantum catch states of all receptors the set of all receptor outputs the bridge locus subjective visual perception The bridge locus is necessary for subjective visual experience.Linking proposition =df a particular mapping occurs, or a part

9、icular mapping principle applies, between perceptual and physiological states.The Similar Family Similarity Similar Similar 2. Contrapositive Similar Dissimilar Dissimilar 3. ContrapositiveSimilar Similar 4. Converse SimilarDissimilar Dissimilar The Mutual Exclusivity FamilyMutual Exclusivity Mutual

10、ly Exclusive (physiological terms) Mutually Exclusive (psychological terms)Mutually exclusive neural states will correspond to sensations which never occur together2. Contrapositive Mutual ExclusivityMutually Compatible Mutually Compatible If two sensations can occur together, their corresponding ne

11、ural signals must also be compatible3. Converse Mutual ExclusivityMutually Exclusive Mutually Exclusive If two sensations do not ordinary occur together, there exists a stage of neural processing, at or before the bridge locus, at which the neural codes for the two sensations are mutually exclusive.

12、4. Contrapositive Converse Mutual ExclusivityMutually Compatible Mutually Compatible If two neural signals can occur together, their corresponding sensations must also be compatibleThe Simplicity FamilySimplicity Simple (physiological terms) Simple (psychological terms) Simple states of the nervous

13、system will produce simple sensations2. Contrapositive Non-Simple Non-Simple Non-Simple 3. Converse Simplicity Simple Simple Simple sensations imply the presence of particular elements of simplicity in the neural code4. Contrapositive Converse Simplicity Non-Simple Non-Simple The Analogy Proposition

14、 (physiological terms) “looks like” (psychological terms) explains If psychophysical and physiological data can be manipulated in such a way that they can be plotted on meaningfully similar axes, such as the two graphs have similar shapes, then causal relation can be established.Specific Linking Pro

15、positions Involving Single CellsMach bands terms: activities of single neurons or regular populations of single neurons Argument (involving the analogy proposition): The physiological data “look like” the psychophysical data the physiological data explains the psychophysical dataMach Bands Mach Band

16、s (Mach 1865) Bright and dark lines that appear near the brighter and darker borders of a blurred edge between two uniform regions of different luminance. Retinal ganglion cells But to what extent, these result explain Machs band? The implicit linking proposition: The set of firing rates across a ro

17、w of ganglion cells maps to the set of perceived brightness across the visual fieldThree reservations about the implicit linking proposition Intended range of applicability Assumption of homogeneity of a class of ganglion cells Peripherality (at retina) “Line detectors” play a fundamental role in th

18、e perception of oriented contours. Some visual scientist have also speculated that cells with even more specific trigger features will be found at higher levels of the visual system.Single CellsTrigger features or detectors A neurons role in the neural code is to signal the presence of the stimulus which makes that neuron respond most vigorously.The implicit linking proposition in trigger featuresRese