SINGLE WORD VISUAL LEXICAL DECISION
On each of these pages is a simple example and sometimes a more complex example. Each complex example introduces a new parameter/switch.
<n 16>1 <azk>2 <cr>3 <fd 38>4 <t 2000>5 <id "PIO12">6 <id "keyboard"> <dbc 0>7 <dwc 000255000>8
09 "Press SPACEBAR to start"10;11
+112*13 "RABIES" /;14
-2 * "BRANTLY"/;
-3 * "SKELVE"/;
+4 * "GAME"/;
+5 * "BACON"/;
+6 * "ASH"/;
-7 * "GRADDLE"/;
+8 * "FAKED"/;
0 <Bell>15 "End of Part 1. Press SPACEBAR to continue";16
-9 * "LUNCE"/;
+10 * "STALE"/;
+11 * "HEDGE"/;
-12 * "SMARKLE"/;
-13 * "INDRASTAL"/;
-14 * "SNOTHS"/;
+15 * "BELIEVE"/;
-16 * "EMBRINT"/;
0 "The End. Thank You.";17
Empty lines at the top of your control file will cause the file to fail
1 Number of test items. That is the number of items with unique ID numbers. Repeated numbers for fillers and 0's should not be included in this.
2 Output is in ASCI text format.
3 Continuous Running. Without this each trial would have to started by pressing the spacebar. For something like a self paced reading experiment then you would not want continuous running.
4 Frame duration in ticks. What is a tick?. In fact it actually sets the time that the next frame is scheduled, as opposed to the actual duration of the frame
5 Time out. How long the subject has to respond before the machine automatically caries on. Time outs are recorded as errors in the output with RT at whatever TO is set to. Without this the DMDX defaults to a time out of 4000ms.
6 Input device, the first one is the button box. The second on is, this is a hard one, the keyboard. The keyboard is the default. The default keys are right shift key 'YES', lef shift key 'NO', spacebar 'request'. You can specify more than one type of input device as above.
7 Default Background Colour. '0' is black.
8 Default Writing Colour. '000255000' is green. 000000255 is blue, 255000000 is red. Each 3 digit block refers to a colour. Black is a special case and is <0>. White is 255255255. You can vary the darkness of a colour. 000100000 is a faint green.
9 '0' is the ID number for non-test lines in control files. Lines for giving instructions, etc.
10 Text to printed to the screen should be enclosed in quotes, "".
11 Semicolons mark the end of an item. Every item and every instruction must be terminated with a semicolon.
12 Item ID number. All items for which RT's are to be recorded need a unique ID number. RT's are stored and labelled with this ID number. '+' means correct response is YES. '-' means correct response is NO. A wrong response is marked with a minus sign in the output file.
13 Clock on. Start recording RT from this point, here the onset of the visual display.
14 Backslash '/' is the frame delimiter. Here it is needed to make the text be displayed for the time specified in the frame duration parameter. Without the backslash the word will be erased when the subject responds and DMDX will go onto the next item. See the tips page for more on frames.
15 <Bell> plays the computer bell/buzzer to sound.
16 No backslash here, so that program stops until space bar is pressed.
17 No backslash as this the last item.
A more complex form of the above design might be as below...
N16 <s 16>1 <d 20>2 <azk> <cr> f38 <t 2000> <id "PIO12"> <id "keyboard"> <dbc 0> <dwc 000255000> <vm 800,600,600,16,0>3
$4
0 "Press SPACEBAR to start";
$
+1 * "RABIES" /;
+2 * "ASH" /;
+3 * "BACON" /;
+4 * "GAME" /;
-5 * "GRADDLE" /;
-6 * "LUNCE" /;
-7 * "BRANTLY" /;
-8 * "SKELVE" /;
$
0 <Bell> <ln -2>5 "Have a Break",6 <ln 2> "Press SPACEBAR to restart";
$
+9 * " BELIEVE"/;
+10 * "STALE"/;
+11 * "HEDGE"/;
+12 * "FAKED"/;
-13 * "INDRASTAL"/;
-14 * "SNOTHS"/;
-15 * "SMARKLE"/;
-16 * "EMBRINT"/;
$
0 "The End. Thank You.";
$
This design scrambles the order of presentation of the items so that each time the experiment is run, the items will be presented in a different order. There is more on scrambling on the tips page.
1 Scramble. The number is the block size. It is 16 here, which means the whole 16 items are treated as one block for scrambling. If it was 8, the first 8 items would be scrambled as one block and as would the second. If your experiment is for example split into two halves, it would be best to make sure each half has equal numbers of test stimuli and randomise within each half.
2 The delay parameter 'd' controls the inter-trial interval and is given in ticks. The inter trial interval is the time between the end of one item and the start of the next. The default is 48 ticks. It is, however, only a minimum delay, the delay is timed from the point at which the preparation of the next item is completed. See the tips page for more on this.
3 The video mode parameter, vm, sets the screen size and colour depth. Here it is 800 by 600 pixels and 16 bit colour. This will give reasonable looking fonts and enough colour depth to show most bitmap images. If you have a large-ish image and you use too low screen resolution, only half the image may be on the screen. If you don't have enough colour depth, then the image will look very poor. Try playing around with these parameters to find the most suitable ones for what you want to do. For instance Arabic characters are more curved than Latin and will look worse at lower screen resolutions. Upping resolution or colour depth increases video memory load. If you have only lowish video memory on a machine, say a laptop, you can use an image editor to reduce the resolution of your pictures themselves, e.g. from 32 bit colour to 16 bit colour. This worked fine here at the CBU.
4 The dollar signs above and below lines mean that these items will not be scrambled. They will be displayed in their original position.
5 <ln -2>. Write the text 2 lines above centre line. <ln 2>. Write the text 2 lines below centre line
6 The comma delimits the frame, allowing the two pieces of text to be displayed simultaneously.
-- Main.CarolineWhiting - 23 Mar 2007