Kenny Smith is one of my computational linguistics professors in Edinburgh University. He is great at guiding you through complex mathematical concepts related to language, with a northern accent and a laid-back attitude. On his series of papers about linguistic models of language acquisition, he covers a very wide range of issues in the evolution and transfer of language through cultural interaction and with the help of some learning biases. He made models of language generation, acquisition, maintenance and creation. These proved ecologically relevant, since they predicted (or followed) the findings from empirical studies on developmental psychology. On his paper “Inferential Transmission of Language” from 2005, he explores the very interesting issues of Lexical acquisition in infants and provides computational models to simulate them. This article will provide a short, read-me-before-the-exam synopsis and evaluation of the main issues Kenny brings forward.

Continue reading ‘Inferential Transmission of Language [notes on cognitive science]’

On the paper “On learning the Past Tenses of English Verbs”, Rumelhart and McClelland aim to explore the ability of networks to extract rules from the input given to them in a different fashion to what traditional rule systems use. This arises in connection to the argument about the LAD  (Language Acquisition Device), where humans are born with innate ability to extract and process rules in language from a very poor input. They built a network that simulates past tense acquisition in children based on the following stages from developmental psychology:

  1. Children use only a small number of verbs in the past tense, all high-frequency words. Most of them are irregulars. There’s no evidence of the use of any rules.
  2. Evidence of implicit knowledge of a linguistic rule emerges. Children use a much larger set of verbs in the past tense.
    • The child can now generate a past tense for an invented word (i.e. rick – ricked)
    • Children supply incorrect regular past-tense endings for words they used correctly in stage 1
  3. Regular and irregular forms co-exist. Children regain knowledge of the correct irregular forms, and they apply the regular form to new verbs. This persists into adulthood.

These stages (as everything in psychology) aren’t really distinct and sequential, but in fact they are rather gradual.

Continue reading ‘Learning Past Tenses of English [notes on cognitive science]’

While the connectionist approach shows great potential and it has been at the forefronts of many an advance in the field of cognitive science and AI in general, there still remain a number of important challenges. Let’s have a look at Elman’s favorite issues. Continue reading ‘Issues in Connectionist Models [notes on cognitive science]’

On the book Rethinking Innateness, by Elman et al, we’re given an introduction to the advantages of connectionism as an explanative model of human development and language acquisition. Connnectionist models are usually built up of a number of nodes interconnected by communication channels. These nodes recieve biased activation and depending on their internal threshold function, they send an activation themselves. Nodes can be connected and arranged in an innumerable amount of structures, from a simple layered network to incredibly complex multi-modular structures. The connections between the nodes have weights and it is there where the knowledge of the network is stored. 3 Layer Feed-Forward network

These weights are always real valued and they alter the input value by multiplying it by their own value. So if a node with a weight of -2.0 receives an input of 0.5, the resulting output would be -1.0, an inhibitory signal. (if the result was positive, the signal would be excitatory. We call the net input of any given node the sum over all input nodes of the products of the activation and the weight of the input. Now the node has an internal response function that will output a value according to the net input.showequation This is usually a threshold function, which will output on the range of 0 to 1, in relation to the input. The most commonly used are the sigmoid function, or the logistic function. For very large inputs, they will output 1, for very small (negative) inputs, they will ouput 0. When the input is close to 0, the output will be in the range of 0 to 1. Changing the threshold function will give us either more sensitive thresholds or more abrupt ones. The “magic” of these systems is that their nonlinear response allows for fine-grained distinctions of categories that are continuous in nature. In practice however, we usually regard the outputs as zero or one. (more on this later). Bias nodes are always on, and they allow us to set the default behavior of other nodes in the absence of input.

Continue reading ‘The Connectionist Approach [notes on cognitive science]’

In this paper by Frank Jackson, he introduces himself as a ‘qualia freak’. He argues that certain sensations and experiences cannot be accounted by a physicalist approach. A physicalist approach only considers physical information to be the “correct” kind of information, yet he argues that there are things that cannot be described just in terms of physical information, such as the smell of a rose, seeing the sky, feeling pain, etc; therefore physicalism is false. He acknowledges that this argument has little polemic validity. He tries to fix that by elaborating on what he calls “the knowledge argument”.

Continue reading ‘Epiphenomenal Qualia [notes on cognitive science]’

In this article Nagel draws our attention towards the role of consciousness in the mind-body problem, attacking reductionist theories. He tries to show that there is no reduction concept available to deal with consciousness and goes on to explore these implications, by beginning with an account of the nature of consciousness.

Continue reading ‘What is it Like to be a Bat? [notes on cognitive science]’

Terrence Horgan and James Woodward defend Folk Psychology on their paper “Folk Psychology is Here to Stay” from the attacks of Churchland and Stich, arguing that none of them has provided convincing reasons for doubting Folk Psychology as a method of explaining individuals. They base their critique on the overly stringent conceptions of the interactions between FP and other lower level theories. They define FP as consisting of two components: theoretical principles (universal closures of conditional formulas) and an existential thesis (that our FP descriptions of people are true and they do undergo the FP events attributed to them). Horgan and Woodward claim that Stich and Churchland argue against the existential thesis, by denying the existence of beliefs, desires and intentions. Horgan and Woodward thus claim that FP provides a useful framework for prediction and genuine causal explanations.

Continue reading ‘Folk Psychology is Here to Stay [notes on cognitive science]’

On this paper, Churchland explores folk psychology.

It is clear that any human can explain the behavior of other persons with remarkable accuracy. Each understands others because we share knowledge about the relations between external circumstances, internal states and behavior. This is called folk psychology.

The other minds problem states that the conviction that an individual is subject of certain mental states is not inferred deductively from his behavior. Rather, it is a explanatory hypothesis that provides explanations, predictions and understanding of the individual’s behavior. A Martian could do this, even if its own psychology was wildly different from ours, and he wouldn’t be generalizing from his own case.

The attitudes described in folk psychology can be compared to the ‘numerical attitudes’ shown by physical objects in terms of mass, velocity etc. which allow for generalization across attitudes that hold in nature. Therefore folk psychology is a theory, and it is striking that philosophers took so long to realize so. This means that the body-mind problem can be realized in terms of how the ontology of the folk psychology theory will be related to the ontology of neuroscience.  So will folk psychology be reducible in terms of another theory, perhaps a better one? Continue reading ‘Exploring Folk Psychology [notes on cognitive science]’

It is hard to think why random squiggles on this screen are triggering what we call “mental pictures” in your head. Putnam tried to account for this on his essay “brains in a vat”. More after the jump:

Continue reading ‘Brains in a Vat [notes on cognitive science]’

Dennet had the great idea of “formalising” folk psychology by ascribing beliefs, desires and intentions to objects in order to describe and predict their behavior. This is called the intentional stance, in which one predicts the most rational behavior of the object described according with the current beliefs held by it. This means assigning the object the beliefs it ought to have according to its perceptual abilities; the desires it ought to have given its biological needs and finally the behavior that would be rational given the beliefs and desires it holds.

This sounds very good, because we make no commitments about the internal workings of the system nor its design or program. Therefore, if we have two robots designed to act exactly like you, mimicking every single action you do, in the context you do them; they wouldn’t be any different from each other or from you from an intentional point of view. This means that describing an object as an intentional system does not entail anything about its physicochemical nature or functional design, and neither neurophysiology nor ”subpersonal cognitive psychology” could possibly show that the object is not an intentional system. These new concepts are identical with folk psychology, but they are better, since they capture its essential notions. These must be comparable to the older folk notions when it comes to describing ourselves.

However, accepting the intentional stance notions of Belief and Desires (which we will call ISBelief and ISDesire) would not allow us to describe human behavior, since a great deal of the time humans behave quite irrationally. However, the intentional stance assumes perfectly rational systems so attributing inferential failings and inconsistent beliefs to them makes no sense. How would you explain suicides, smokers and so forth? Dennet takes two routes. The first, called by Stich “The hard line” sticks to the idealized notion of intentional systems and tries to minimize the importance of the differences between IS beliefs and intentions and their folk-psychology counterparts. He uses arguments springing up from evolutionary optimality: if an organism is the product of natural selection, we can assume most of its beliefs are true and their belief generation strategies rational. The “soft line” legitimizes human faliability, by deriving “imperfect intentional systems” from the idealized ones explained above. However, this would be like adding a tolerance rule to chess such that any game can be considered legal as long as there are at most k illegal moves of chess.

Stich aims to step away from Dennet’s theory by reshaping it. There are two main points. First, rather than an instrumentalist view of folk psychology, he takes a functional one: belief states are functional states which play a role in the causation of behavior. Second, in ascribing content to belief states, we are not comparing others to an idealistic rational entity, but to ourselves. This makes it possible for three people reading about an earthquake on different sources have the same belief that the earthquake actually happened, and it accounts for the fallibility of human reasoning.

from “Dennet on intentional systems” by Stephen P. Stich