APPENDIX VI

Description of CANTAB tests used A. Intra/Extra-Dimensional Shift

A1 Display

Figure A Display of the IED Shift Test

Two artificial dimensions are used in this test, colour-filled abstract shapes and white lines. Simple stimuli are made of just one of these dimensions, whereas compound stimuli are made-up of both, namely white lines overlying colour-filled shapes. Subjects progress through the test by satisfying a set criterion of learning at each of nine stages (six consecutive correct responses). If at any stage the subject fails to reach this criterion after 50 trials, the test terminates (CeNeS Cognition, 1998a).

A2 Task

The test starts with the presentation of two simple, coloured-filled shapes. The subject must learn which of the stimuli is correct by clicking on it with a mouse. Once criterion is reached the contingencies are reversed so that now the previously incorrect stimulus is correct. The second dimension is then introduced, initially lying adjacent to, and then overlapping the first dimension. The contingencies do not change, remaining the same as at the end of the simple discrimination. Once criterion has been reached with the overlapping compound stimulus, the contingencies are reversed within the original dimension. It is important to note that the second dimension is entirely redundant to the solution of the problem at this stage.

Once the subject has learned the compound discrimination, new compound stimuli are presented, till varying along the same two dimensions of shape and line. Subjects are initially required to continue to attend to the previously relevant dimension of shape to learn which of the two new exemplars is correct (the intra-dimensional shift). For the next stage subjects are required to shift attention to the previously irrelevant dimension and learn which of the two exemplars in this dimension is now correct (the extra-dimensional shift) (CeNeS Cognition, 1998a).

A3 Standardised instructions

Go into this test before explaining the instructions. Say:

 

Now you can see two patterns. One of the patterns is correct and the other is wrong. What you have to do is click with the mouse on the one you think is correct. There is a rule that you can learn and follow to make sure you get it correct each time. The computer will keep track of how well you are doing and when it is clear that you know the rule, the computer will change it, but remember, this will not happen very often. When the rule is changed you will have to think of a different rule in order to go on doing well. To begin with, there is nothing on the screen to tell you which of the two patterns is correct so your first choice will be a simple guess. However, the computer will give a message after each attempt to tell you whether you are right or wrong. You can start now.

If they hesitate, prompt with:

Just guess this first time. Choose now.

If they get it correct, say:

Good, now keep on trying to get it correct.

If they get it wrong, say:

Bad luck, now try to get it correct.

When the subject makes their first mistake at a rule change say:

 

Now remember, the rule will change at some point.

From "CANTAB User Manual: The Parallel Batteries," by CeNeS Cognition, 1998a, pp. 40-41. Copyright 1998 by CeNeS Limited, Cambridge, UK. Adapted with permission of the authors.

 

A4 Main data items recorded

  • stage reached (maximum 9)

  • total errors

  • errors at ED-shift

  • errors up to ED-shift
  •  

B. Rapid Visual Information Processing

B1 Display

Figure B Display of the RVP Test

This test has a 2-minute training period before the actual 4-minutes test is run. In both training and actual test a white box appears in the centre of the computer screen, inside which digits from 2 to 9, appear in a pseudo-random order, at the rate of 100 digits per minute. Subjects are required to monitor the changing digits for pre-defined number sequences and to respond by pressing a button at the presentation of the final digit of the sequence. Their reaction time is not measured (CeNeS Cognition, 1998a).

B2 Task

In the test itself subjects are requested to detect three particular sequences of digits, 3-5-7, 2-4-6, and 4-6-8, and to register responses with a button press. However in the training period, the subject is requested to press the button only when there is a 3-5-7 sequence. During this training period the target sequence will also appear red, underlined in yellow, and the computer will give feedback whether the button was pressed correctly or not. These cues are all phased out by the end of the two-minute training period. In the test itself there are no cues whatsoever.

Target sequences occur at the rate of 9 every one-minute, with each target sequence appearing three times in each minute. For scoring purposes CANTAB calculates the number of responses recorded a having occurred within 1800 milliseconds of the final digit presentation for each of the target sequences. CANTAB also records false alarms, defined as occasions in which the subject incorrectly identified a target sequence. Finally, CANTAB also records and reports the mean hit response latency (CeNeS Cognition, 1998a).

B3 Standardised instructions

Training stage

The computer displays Please Wait and an empty box with the number 357 next to it.

Now give the following instruction:

 

 

You are going to see some numbers appearing one at a time in a box in the centre of the computer screen. What you have to do is to look for a target sequence of three numbers and press the ad whenever you spot the target. The target sequence will be a '3' immediately followed by a '5', immediately followed by a '7'. It is only when you see the last number of the sequence that you should press the pad. To begin with you will know that a sequence has begun because the target sequence will appear in red and be underlined in yellow. There will also be a Correct message from the computer if you press the pad correctly. As the practice sequence progresses you will find that these cues will gradually be phased out.

Now begin the practice session. If the subject responds too early, say:

 

Wait until you see the last digit before pressing the pad.

At the end of two minutes the training phase will end and the computer will again read Please Wait.

 

Test phase

When the screen reads Please Wait and displays three sequences of numbers give the following instructions:

 

 

This time you will do the same thing, but there will now be two other sequences you have to remember, 2-4-6 and 4-6-8 as well as 3-5-7. Whenever you see any of these three target sequences you should press the button when the 3rd digit appears. The test will last for four minutes so please try to concentrate until the end. The target sequences will remain on the screen to help you remember them. However, try to concentrate on the box in which the numbers are changing. Please respond as quickly as you can whilst trying to avoid making mistakes. Take a few seconds to familiarise yourself with the three different sequences, 3-5-7, 2-4-6 and 4-6-8. Remember there will be no colour, no underlining and no cues from the computer.

From "CANTAB User Manual: The Parallel Batteries," by CeNeS Cognition, 1998a, pp. 36-37. Copyright 1998 by CeNeS Limited, Cambridge, UK. Adapted with permission of the authors.

 

B4 Main data items recorded

  • probability of hit - this is the probability of the subject responding correctly, equal to the hits / (hits + misses)

  • probability of false alarm - this is the probability of a false alarm, equal to false alarms / (false alarm + correct rejection)

 

C. Paired Associates Learning

C1 Display

Figure C Display of the PAL Test

Six boxes are displayed on the screen. All are opened in a randomised order. In one of them there is a pattern, and the subject is requested to remember its position and later click on the appropriate location with a mouse. After the first trial the subject will have more object associated with different locations to remember (CeNeS Cognition, 1998a).

C2 Task

In essence the subject is required to remember patterns associated with different locations on the screen, and during the test phase, as each pattern is presented, point to the appropriate location. After the last box has been closed the patterns are shown in the middle of the screen and the subject must click on the box where the patterns were located. If the choices are correct, the procedure is repeated with two new patterns. If either choice was incorrect all the boxes are reopened (the reminding phase), after which the subject must choose again. The test starts off at a very simple level with only one pattern to recall. After two correct sets with a single pattern, the number of patterns is increased to two for two sets, then to three for two sets, and then to six and finally eight for one set each.

The subject may have up to ten repeat reminder presentations for each set of patterns to learn the list. If any list has not been correctly completed within ten presentations the test is automatically terminated (CeNeS Cognition, 1998a).

C3 Standardised instructions

One pattern (two trials at this level)

Go into this test before explaining the instructions. There is one demonstration set followed by test sets. Now say:

 

 

 

This time there will be six boxes. Each box will open up. There will be a pattern in one of the boxes and you have to remember which box it is in.

When the pattern appears, say:

There is the pattern. Try to remember which box it is in.

Make sure that the subject is looking at each box in turn. When all the boxes have been opened, the pattern appears in the middle of the screen. Say:

 

 

 

Click on the box where you saw that pattern appear.

When the subject chooses if the subject got it right, the screen will display All Correct. Now say:

 

 

Now we are going to do the same thing again, but this time with a different pattern.

However if the subject has made an error on this or subsequent trials, use the instruction:

 

 

You made a mistake, but you get another go to get them all right. Look carefully. The boxes will open up again to show you where the patterns really belong. Now have another go.

At the end of the second correct set with one pattern the computer will display All Correct. 2 New Shapes.

 

Two patterns (two trials at this level)

Now say:

This time there will be two patterns to remember. Each box will open up. You have to remember which pattern is in which box.

As the patterns appear, point to them and say:

 

There is one pattern… and there is the other pattern.

When all the boxes have been opened, the patterns appear in the middle of the screen, one by one. Say:

 

 

So which box was that pattern in? And, which box was that pattern in?

Three patterns (two trials at this level)

Say:

This time there will be three patterns

Six patterns (one trial at this level)

Say:

This time all six boxes will have a pattern inside and you have to remember which pattern goes in which box. You may not get this correct first time, but you can have more goes until you do. Just try to do the best you can.

Eight patterns (one trial at this level)

Say:

Now there will be eight boxes. Each box will have a pattern inside and you have to remember which pattern goes in which box. You may get this all-correct first time, but you can have more goes until you do. Just do the best you can.

From "CANTAB User Manual: The Parallel Batteries," by CeNeS Cognition, 1998a, pp. 28-32. Copyright 1998 by CeNeS Limited, Cambridge, UK. Adapted with permission of the authors.

C4 Main data items recorded

     

  • stage reached (maximum 8)

    •  

  • total errors

    •  

  • mean errors to learn

D. Spatial Working Memory

D1 Display

Figure D Display of the SWM Test

The test begins with a number of coloured boxes being shown on the screen. The aim of the test is for the subject to find a blue token in each of the boxes and use them to fill up an empty column on the right hand side of the screen. The number if boxes is gradually increased until it is necessary to search a total of eight boxes. The colour and position of the boxes used are changed from trial to trial to discourage the use of stereotyped search strategies (CeNeS Cognition, 1998b).

D2 Task

The subject must click on each box in turn until one opens with a blue token inside (a search). Returning to an empty box already sampled on this search is an error. When the blue token has been found, the subject has to place it in the right column by clicking on the right-hand side of the screen. The box that contained the blue token will not obtain another one on this trial. Returning to this box is also an error. The subject must then begin a new search for the next blue token. It may be in any of the boxes that so far have remained empty.

The order in which the subject searches the boxes is determined by the subjects themselves, but the number of empty boxes they must visit (discounting errors), is determined by the computer. At the end of each trial, when the column is full, a COMPLETE message is displayed followed shortly afterwards by the message NEW SET. The sets vary in size from three boxes to eight boxes. The black column must be filled with as many tokens as there are boxes (CeNeS Cognition, 1998b).

D3 Standardised instructions

Set 1

Demonstrate with the first trial and then let the subject practice on the second trial. Say:

 

 

For this test, you will see some coloured boxes on the screen. What you have to do on each go is to look for a blue token that the computer has hidden inside one of the boxes. Only one token will be hidden at a time. You have to collect enough blue tokens to fill the black hole ('home') on the right of the screen. To look inside a box just click on it.

Click on one of the boxes:

This box does not have a blue token in it so I shall try a different box.

Click on another box:

 

Click on the white column or black hole on the right hand side of the screen.

This box has a blue token inside it and now I am going to move it here to fill the black hole.

The following instruction is of crucial importance and must be strongly emphasised:

Point to the one you have just used.

 

Now I have found a blue token in this box…

… there will never be one in there again, so I must not go back to it. There are two more blue tokens to find, but the computer never uses the same box twice for the blue token, so I must click on another one.

Click on another.

There is no token inside this box, so I will try another.

Click on the box you have not yet found a blue token in to reveal the blue token, and then click on the RHS of the screen

 

 

Now I have found two tokens and the last one must be here.

Click on the only box in which you have not yet found a blue token and then click the RHS of the screen.

 

Now I have found all three tokens and I have finished because I have filled the black hole completely with blue tokens.

The computer will display Completed. After a pause the words New Set will appear. Say:

 

 

Now you have a go

Set 2

Say:

Click on one of the boxes to search for a blue token.

Click on one of the boxes:

This box does not have a blue token in it so I shall try a different box.

The subject should click on one of the boxes containing a token.

Now you have got one blue token to fill the black hole.

Look for another one, but remember that it will be in a different box this time.

Set 3… 16

There are in all four practice sets with 3 boxes and then the computer will move onto the test trials which will include four sets with 4 boxes, four with 6 boxes and four with 8 boxes.

 

From "CANTAB User Manual: Working Memory and Planning Battery," by CeNeS Cognition, 1998b, pp. 24-29. Copyright 1998 by CeNeS Limited, Cambridge, UK. Adapted with permission of the authors.

D4 Main data items recorded

     

  • Between errors - occasions when the subject returns to a box in which a token has already been found

  • Strategy score
TOP

<-  Main  ->