1. Introduction to Cognitive Science Lecture #2 : Mental Representations Joe Lau Philosophy HKU

2. Classical cognitive science Assumption #1 : Mental states are constituted by mental representations. Assumption #2 : Many mental states have complex structure.

3. Defending A1 Mental representations Encode meaning and knowledge Explains how mental states can interact with the brain and body No alternative way to explain mental phenomena.

4. Defending A2 Structured representations : Explain how we can have new thoughts that relate to old ones systematically. Provides a good framework for studying various mental processes such as reasoning and language understanding. White dog Black cat Whit e cat Black dog

5. Theory of content Mental representations have content. Philosophical question : what is it that determines the content of a representation? How can we tell whether a state of the brain has content or not?

6. Artificial representations Examples : Diagrams, signs, natural languages, gestures The assignment of meaning is arbitrary in that there is no necessary connection between a representation and its meaning. Depends on conventional usage. “WHITE DOG” 

7. Problem A theory of content that invokes conventions is not applicable to mental representations. Conventions depend on the beliefs, which is what mental representations are supposed to explain.

8. Visual Perception Topographical representation of visual stimulus in area V1

9. Causal correlation? A simple causal theory of meaning X represents Y in a creature Z = when Z is functioning normally, X is caused by Y and only by Y. YX normally causes represents

10. Criticism #1 Not all causal correlations involve representations. For example, the pumping of the heart normally causes blood circulation, but the latter is not a representation of the former.

11. Response The attribution of representations should be governed by bottom-up and top-down motivations. It should be part of a theory that explains where the content of the representation derives from and how the content is used. Representations are supposed to play an informational role.

13. Criticism #2 The theory does not apply to conceptual representations. Perceptual representations Representations involved in perception. Detects real-time properties Conceptual representations Representations involved in thinking and reasoning. Do not function as detector representations.