Reading

[Required] Section 4.1 "Intentional States and Intentional Content" in Tye, Michael (1995) Ten Problems of Consciousness : A Representational Theory of the Phenomenal Mind Representation and Mind MIT Press.
[Required] Aydede, Murat, "The Language of Thought Hypothesis", The Stanford Encyclopedia of Philosophy.
Fodor, J. and Pylyshyn, Z. (1988) "Connectionism and Cognitive Architecture" in Cognition 28, pp. 3-71.
Section 3 of Block "The Mind as the Software of the Brain"
Braddon-Mitchell & Jackson (1996) Philosophy of Mind and Cognition Blackwell.

The language of thought (LOT)

The LOT hypothesis says : intentional mental states are mental representations that are language-like in having a combinatorial syntax and semantics.
Combinatorial syntax = the mental representations are either complex or atomic, with the former being made up of the latter according to a system of rules.
Combinatorial semantics = the content of a complex representation depends on its syntax and the content of the atomic representations
It does not imply :
- LOT is innate.
- Everyone has the same LOT.
- LOT is a natural language e.g. English.
- LOT requires interpretation by an agent.

We should accept LOT because LOT provides the best explanation of such phenomena:

It explains how intentional states can causally interact with perception, behaviour and other mental states.
It explains systematicity, that to have one belief you need to have other beliefs which are systematicity related in content. If you can think a is F, b is G, then you must be able to think a is G, and b is F.
It explains productivity, that there are indefinitely many beliefs we can have.
It also explains opacity, that one can believe that x is F without believing that y is F even though x = y.
It also provides a model of reasoning that consists in rule-based operations on representations according to their syntactic structure.

These phenomena support LOT only if we cannot find better explanations of these phenomena.

According to such a theory intentional mental states are map-like and not language-like.
See Braddon-Mitchell and Jackson for some differences between map-like and language-like representations.
The map theory can also explain causal interaction, systematicity, productivity, opacity.

It does not seem to provide a good model of reasoning.
What about abstract concepts, e.g. beliefs about logic or mathematics? How about conditional or disjunctive beliefs, or beliefs about unobservable objects?
Does it take longer to form a belief about objects with a complex appearance?
It is possible that we are conscious of only one particular thought or belief. But this is often not possible with a map-like representation.
This does not mean that there are no map-like representations. We do experience having mental images and prima facie they are more like maps and pictures than sentences. However, some people argue that mental images are actually language-like.