Dec1999 CO230 : Cognitive Science (Question 1)Suggested Solutions

(a)

Some cognitive scientists adopt an information processing approach to studying the brain.Briefly describe this approach,and justify whether you think it is appropriate or not.

Maximum of (3)for the description, (1)for explaining why
In this approach,the brain/mind is modelled as an information processor (computer) (1)where informatitoon is stored as declarative knowledge (computer memory) (1) and processes are stored as procedural knowledge (computer programs) (1). In this
approach,the processes are performed sequentially (1). A typical justification might be that as the brain processes information in parallel,this approach may not be an appropriate representation of the brain (1).

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(b)

Symbolic and neuro-cognitive systems both have their strengths and weaknesses.For each of the following applications,state which approach is more appropriate and justify your answer.As part of your answer,you should also briefly describe how the approach would be applied to the application.(Note:marks will not be awarded if no
attempts are made to explain the rationale of the choice.)

(i)Character recognition.[3 marks ]

Other suitable answers should be awarded marks.
(1)for a brief description as to how the method can be used for the application;(1) for the correct identification of a suitable method with a weak explanation;(2 )for the correct identification of a suitable method with a strong explanation.

•Neuro-cognitive system:
–Input is in the form of a 2-dimensional array of pixels.The loss of a
proportion of pixels may not affect the recognition process.
–In an unconstrained environment,there may be a large number of
character sets to train.The adaptability of neural networks makes it
appropriate in this application.

•Symbolic system:If some preprocessing is performed to extract features of each character,the features can be represented as symbols.Then the rule based (symbolic)systems can be used to perform this task easily.

(ii)An expert system giving medical advice.[3 marks ]

Other suitable answers should be awarded marks.
(1)for a brief description as to how the method can be used for the application;(1) for the correct identification of a suitable method with a weak explanation;(2)for the correct identification of a suitable method with a strong explanation.

•Symbolic system:Medical facts can be easily represented in symbolic systems.Rules allowing manipulation of the facts and inference can be used to give
advice.

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(c)

Given the following statements:

If it rains then I am wet.
I am not wet

What information can be inferred?(You should show all your working and identify the logical rules used.)

rain : it rains
wet : I am wet
rain => wet
~wet =>~rain [contrapositive ]
( ~wet ( ~wet =>~rain)) =>~rain [modus ponens ]

We can conclude that it is not raining

Correct steps in the working (1),specifying the two logical rules used (1),correct conclusion (1).

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(d)

For the game of tic-tac-toe (also known as noughts-and-crosses),there are two players, one plays the nought,the other,the cross.The players take it in turn to place their respective symbols in one of the unoccupied spaces on a 3x3 board.The first player who manages to place three of their symbols in line across any row,column or diagonal will win the game.The following diagram represents a mid-game board state:

1

1

1

O

1

1

X

O

1

(i)Generate the state-space diagram for the next move,clearly numbering each of the next possible moves for easy reference when answering parts (ii)and . [1 mark ]

(1)for correct diagram

(ii)From this set of next possible moves,identify those which should not be made, as they would lead to losing the game.Explain your choice.
[3 marks ].

You must not make a move that will result in states 1,3 and 6.If you do,the opponent will place his symbol in the middle of the board,thus opening two opportunities for him to win.When it is time for you to make a move again,you can only block one of his opportunities,and you will lose the game.(1) for correct answer; (2)for explanation.

(iii)From this set of next possible moves,identify the single best move to make. Explain your choice.[3 marks ]

From the remaining states 2,4 and 5,the best move would be to achieve state 4. The opponent will then have no choice but to block you,and therefore,you are in control of the game.If you choose states 2 or 5,the opponent may place his symbol at the centre of the board and will gain control.(1)for correct answer;(2) for explanation.

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(e)

The fuzzy set for ages is represented as a graph in two dimensions. Explain the meaning of the slope marked as s in the diagram,with respect to the representation of age.You should refer to the start and end points of the slope,as well as to its angle.

The slope s starts at 10 years,which means that at this age a person starts to be considered a teenager,while still partly being considered a child.At 14 years,the slope ends indicating that from this point onwards,we no longer consider the person as a child,but as a teenager.The angle of the slope indicates the rate of transition from a child to a fully-fledged teenager.(1)for each for the two (1)end points of the slope;(1) for the angle.

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(f)

Most training is supervised,in that the elements in the training set are pairs containing the input to the system as well the desired output.In real life,not all of what we humans are able to do has been taught to us in a supervised manner: we have learnt some concepts through unsupervised experience,when the desired output has not been explicitly stated.

Suggest an example of a classfication task that may be performed by humans,where the concept has been learnt in an unsupervised manner.

Accept other suitable examples

•If a person is given a pail of manufactured parts and told to sort them in two piles, without any further instructions,after looking at a sampling of the parts,the person would notice common characteristics of the parts and start to look for abnormalities.
•If a person is given a large set of slides of blood samples,the person will identify the common features,and notice any slides that have features that are different.

(2)for a complete solution;(1)for a reasonable attempt.

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(g)

Speech can be generated by computer systems through two means: speech synthesis and pre-recorded speech .Briefly describe two problems of pre-recorded speech.

Accept other suitable answers
(1)for each valid point

•Words are recorded in monotone,which sounds unnatural when combined

•There may be problems in extending the vocabulary after a period of time as the person who originally recorded the words may no longer be available.

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(h)

There are proponents and opponents to the concept of intelligent machines.In your opinion,what is meant by “intelligence ”?According to your definition of intelligence, explain whether you think intelligent machines could exist.

Marks awarded to marker ’s discretion.This is an open question with no right or wrong answer.The basic objective is to test the candidate ’s ability to take a stand and justify his stand.
An appropriate definition should receive (1);award a maximum of (2)for the discussion.

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