Philosophy and Cognitive Science Conceptual Role Semantics Joe

Philosophy and Cognitive Science Conceptual Role Semantics Joe Lau Philosophy HKU

Readings n Robert Cummins u Excerpts n on reserve at main office. Ned Block u Online article. u “Advertisement for a theory of semantics”, on reserve.

Topic n Some closely related theories u Conceptual role semantics (CRS) u Computational role semantics u Functional role semantics u Procedural semantics

Three questions about a representational system Which are the representations? n What do the representations mean? n What makes a representation mean what it does? n

Q 1 : Identifying representations Which physical properties / states / objects are used to encode information / carry meaning? n Which are the symbols? n u Information encoded by single neuron in the brain, or groups of neurons? In what form? u Structured? Pictorial? Linguistic?

Q 2 : What do they mean? n Identifying their content / what the symbols represent. means salad in Spanish. u The firing of this neuron represents the boundary of a surface. u “insalata”

Q 3 : theory of meaning n Questions that remains even after the meaning of a representation is known. u Given that X means Y, what explains the fact that X means Y? u What is it for something to have a particular meaning?

Comparing Q 2 and Q 3 n n n Q 2 Specifically about a system of representation. An empirical question to be resolved by empirical investigations. n n n Q 3 A general question about the nature of meaning. A philosophical question about how the concept of representation is to be understood.

CRS A theory of meaning that proposes an answer to the third question. n Better : a very rough and incomplete framework for answering the third question. n

Intrinsic vs. relational properties n An intrinsic property of X : a property that depends only on those properties internal to X. u Example n : the mass of an object A relational property of X : a property of X that depends on objects that exist externally of X. u Example : being a father

Meaning as a relational property n Being meaningful, having a particular meaning are relational properties of representations. u The intrinsic properties of a physical object is not enough to determine its meaning. u The meaning of a representation can change without changing its intrinsic properties.

A unitary theory? n Is there one single theory of meaning that applies to : u meaningful expressions in natural languages u meaningful mental representations

Meaning as covariation n The meaning of a mental representation X depends on what X covaries with. u. X covaries with Y = X causally correlates with Y

Example Hubel and Wiesel : orientation selectivity in the primary visual cortex (area V 1) n Activity of cells represent the presence of bars or boundaries at a certain orientation. n

Criticism n At best : works for “detector” representations that indicate proximate stimulus. u Still : such representations might covary with lots of things. n But not the higher cognitive representations. u Inaccurate covariation u Non-existent covariation

Functional role semantics n Functionalism : Mental states are defined by their functional role. u Role vs. occupant u Intentional mental states are defined by (a) type (e. g. belief) and (b) content (e. g. that snow is white) u So the content of intentional mental states are defined and explained by their functional role.

Functional role = ? ? ? A relational property; role within the functional organization of the mind n Conceptual role semantics (CRS) n u Content defined by the role of a representation in cognition, e. g. reasoning, decision, perception, memory.

Example n Consider these inferential transitions between the beliefs of an agent : P*Q P u P*Q Q u P, Q P*Q u n Interpretation : “*” represents conjunction (“and”). u Meaning determined by role in reasoning.

Advantages of CRS n Explain differences in meaning despite sameness of reference. u Lee : “I have a lot of money. ” u Lee : “Lee has a lot of money. ”

Computational-RS Comp. RS = CRS + Computationalism n Computionalism : cognition is explained by computations. n Mental content defined by conceptual role Mental content defined by computational role (role of representation in the mind’s program) n

CRS and FRS n CRS is one version of FRS u CRS is true FRS is true not FRS is true u There might be aspects of functional role which are not computational. u FRS n e. g. role in interacting with some noncomputational system.

CRS and covariation Internal conceptual role might not determine all aspects of meaning. n External causal connections have a role in determining which particular object a representation is about. n Tung-1 Tung-2

Two factor CRS Which is more important? Internal or external factor n Is this plausible? n u Internal factor imposes constraints on what the representation can be about u External factor determines which particular object or property is represented. u But perhaps some content is determined entirely by the internal factor (e. g. “and”).

Narrow vs. wide content Narrow content : content that depends only on what is inside the head. n Wide content : content that depends also on objects outside the head. n